(a) Steam Heating Boilers.
  (1) Safety valves.
    (A) Each steam boiler shall have one or more safety valves, that are identified with applicable designator with the ASME Certification Mark of the spring pop type, adjusted and sealed to discharge at a pressure not to exceed 15 psig (103 kilopascals). Seals shall be attached in a manner to prevent the valve from being taken apart without breaking the seal. The safety valves shall be arranged so that they cannot be reset to relieve at a higher pressure than the MAWP of the boiler. A body drain connection below seat level shall be provided. For valves exceeding 2 1/2 inch nominal pipe size (65 mm), the drain hole or holes shall be tapped not less than 3/8 inch nominal pipe size (10 mm). For valves 2 1/2 inch nominal pipe size (65 mm) or less, the drain hole shall not be less than 1/4 inch (6 mm) in diameter.
    (B) Each safety valve 3/4 inch nominal pipe size (20 mm) or over, used on a steam boiler, shall have a substantial lifting device, which will positively lift the disk from its seat at least 1/16 inch (1.6 mm), when there is no pressure on the boiler. The seats and disks shall be of suitable material to resist corrosion.
    (C) No safety valve for a steam boiler shall be smaller than 1/2 inch nominal pipe size (15 mm). No safety valve shall be larger than 4 1/2 inches nominal pipe size (15 mm). The inlet opening shall have an inside diameter approximately equal to, or greater than, the seat diameter.
    (D) The minimum relieving capacity of valve or valves shall be governed by the capacity marking on the boiler.
    (E) The minimum valve capacity in pounds per hour shall be the greater of that determined by dividing the maximum Btu output at the boiler nozzle obtained by the firing of any fuel, for which the unit is installed by 1,000, or shall be determined on the basis of the pounds of steam generated per hour, per square foot of boiler heating surface as given in §65.615, Exhibit 7. For cast iron boilers, the minimum valve capacity shall be determined by the maximum output method. In every case, the safety valve capacity for each steam boiler shall be such that with the fuel burning equipment installed, and operated at maximum capacity, the pressure cannot rise more than 5psig (35 kilopascals) above the MAWP.
    (F) Safety valve piping. No valve shall be placed between the safety valve and the boiler or on the discharge pipe between the safety valve and the atmosphere. When a discharge pipe is used, it shall be full size and fitted with an open drain to prevent water from lodging in the upper part of the safety valve or pressure relief valve or in the discharge pipe. When an elbow is placed on the safety valve discharge pipe, it shall be located close to the valve outlet. The discharge pipe shall be securely anchored and supported, independent of the valve. If a muffler is used on a pressure relief valve, it shall have sufficient area to prevent back pressure from interfering with the proper operation and discharge capacity of the valve.
    (G) Safety valves and pressure relief valves shall be installed on the boiler with spindles positioned vertically. The opening or connection between the boiler and any safety valve or pressure relief valve shall have at least the area of the valve inlet.
  (2) Feedwater connections.
    (A) Feedwater or water treatment shall be introduced into a boiler through the return piping system or through an independent feedwater connection which does not discharge against parts of the boiler exposed to direct radiant heat from the fire. Feedwater or water treatment shall not be introduced through openings or connections provided for inspection or cleaning, safety valve, surface blowoff, water column, water gage glass, pressure gage, or temperature gage.
    (B) Feedwater pipe shall be provided with a check valve near the boiler and a stop valve or cock between the check valve and the boiler or return pipe system.
  (3) Low-water fuel cutoffs and water feeding devices.
    (A) All automatically fired steam boilers, except boilers having a constant attendant, who has no other duties while the boiler is in operation, shall be equipped with approved automatic low-water fuel cutoffs installed in such a manner that they cannot be rendered inoperative by the manipulation of any manual control or regulating apparatus.
    (B) The MAWP of all low water fuel cutoff devices shall be set at or above the boiler stamped MAWP.
    (C) When low-water fuel cutoff and feedwater pump controls are combined in a single device, an additional separate low-water fuel cutoff shall be installed. The additional control shall be wired in series electrically with the existing low-water fuel cutoff.
    (D) When a low-water fuel cutoff is housed in either the water column or a separate chamber, it shall be provided with a blowdown pipe and valve, not less than 3/4 inch nominal pipe size (20 mm). The arrangement shall be such that when the water column is blown down, the water level in it will be lowered sufficiently to activate the low-water fuel cutoff device.
    (E) If a water feed device is utilized, it shall be constructed to prevent feedwater from entering the boiler through the water column or separate chamber of the low-water fuel cutoff.
  (4) Pressure gages.
    (A) Each steam heating boiler shall have a pressure gage connected to the device exterior to the boiler. The gage shall be of sufficient capacity to keep the gage tube filled with water and arranged so that the gage cannot be shut off from the boiler except by a cock with tee or lever handle placed in a pipe near the gage. The handle of the cock shall be parallel to the pipe in which it is located when the cock is open.
    (B) The scale on the dial of a steam heating boiler pressure gage shall be graduated to not less than 30 psig (207kilopascals) nor more than 60 psig (414 kilopascals). The travel of the pointer from zero to 30 psig (207 kilopascals) pressure shall be at least three inches.
  (5) Stop valves.
    (A) Single steam heating boilers. When a stop valve is used in the supply pipe connection of a single steam heating boiler, there shall be one used in the return pipe connection.
    (B) Supply and return line. Each supply and return line to a steam heating boiler, which may be entered while adjacent boilers are in operation, shall be fitted with either two stop valves with ample drain between or a stop valve and figure 8 blank. The blank shall be installed between the stop valve and the boiler.
    (C) Type of stop valve. When stop valves over two inches in size are used, they shall be of the outside screw-and-yoke rising stem type or of such other type as to indicate at a distance whether it is closed or open by the position of its stem or other operating mechanism. The wheel may be carried either on the yoke or attached to the stem. If the valve is of the plug cock type, it shall be fitted with a slow opening mechanism and an indicating device and the plug shall be held in place by a guard or gland.
  (6) Bottom blowdown or drain valve.
    (A) Bottom blowoff valve. Each steam heating boiler shall have a bottom blowoff connection fitted with a valve or cock, connected to the lowest water space practicable with a minimum size as shown in §65.615, Exhibit 8. The discharge piping shall be full size to the point of discharge. Boilers having a capacity of 25 gallons (95 liters) or less are exempt from these requirements.
    (B) Drain valve. Each boiler shall have one or more drain connections, fitted with valves or cocks connecting to the lowest water containing spaces. The minimum size of the drain piping, valves, and cocks shall be 3/4 inch nominal pipe size (20 mm). The discharge piping shall be full size to the point of discharge. When the blowoff connection is located at the lowest water containing space, a separate drain connection is not required.
    (C) Minimum pressure rating. The minimum pressure rating of valves and cocks used for blowoff or drain purposes shall be at least equal to the pressure stamped on the boiler, but in no case less than 30 psig (207 kilopascals). The temperature rating of such valves and cocks shall not be less than 250 degrees Fahrenheit (121 degrees Celsius).
  (7) Water gage glasses.
    (A) Each steam heating boiler shall have one or more water gage glasses attached to the water column or boiler, by means of valved fittings not less than 1/2 inch nominal pipe size (15 mm). The lower fitting shall have a drain valve of the straightway type, with opening not less than 1/4 inch (8 mm) diameter to facilitate cleaning. Gage glass replacement shall be possible under pressure.
    (B) Transparent material, other than glass, may be used for the water gage, provided that the material will remain transparent and has proved suitable for the pressure, temperature, and corrosive conditions encountered in service.
  (8) Piping, Fittings and Valves.
Cont'd...
(A) All piping, fittings and valves on the steam line, shall have a pressure rating equal to or greater than the MAWP of the boiler and a temperature rating of no less than 250 degrees Fahrenheit (121 degrees Celsius).
    (B) All piping, fittings and valves other than the steam line, shall have a minimum pressure and temperature rating equal to or greater than the maximum expected pressure and temperature that may be reached.
(b) Hot Water Heating Boilers.
  (1) Pressure relief valves.
    (A) Each hot water heating boiler shall have at least one pressure relief valve, of the automatic reseating type, identified with the ASME Certification mark with the "V" or "HV" designator ASME Code Symbol, and set to relieve at or below the MAWP of the boiler.
    (B) When more than one pressure relief valve is used on a hot water heating boiler, the additional valve or valves shall have a set pressure within a range not to exceed 6 psig (42 kilopascals) above the MAWP of the boiler up to and including 60 psig (414 kilopascals), and 5.0% for those having a MAWP exceeding 60 psig (414 kilopascals).
    (C) Pressure relief valves shall be spring loaded and shall be set and sealed, so that they cannot be reset without breaking the seal. A body drain connection below seat level shall be provided. For valves exceeding 2 1/2 inch nominal pipe size (65 mm), the drain hole or holes shall be tapped not less than 3/8 inch nominal pipe size (10 mm). For valves of 2 1/2 inch nominal pipe size (65 mm) or less, the drain hole shall not be less than 1/4 inch (6 mm) diameter.
    (D) Each pressure relief valve shall have a substantial lifting device, which will positively lift the disk from its seat at least 1/16 inch (1.6 mm) when there is no pressure on the boiler.
    (E) Seats and disks of pressure relief valves shall be made of a suitable material to resist corrosion. No materials likely to fail due to deterioration or vulcanization, when subjected to saturated steam temperature corresponding to capacity test pressure, shall be used for any part.
    (F) No pressure relief valve shall be smaller than 3/4 inch nominal pipe size (20 mm) nor larger than 4 1/2 inch nominal pipe size (115 mm) except that boilers having a heat input not greater than 15,000 Btu/hr (4.4 kilowatts) may be equipped with a rated pressure relief valve of 1/2 inch nominal pipe size (15 mm). The inlet opening shall have an inside diameter approximately equal to, or greater than, the seat diameter. In no case shall the minimum opening through any part of the valve be less than 1/4 inch (6 mm) diameter or its equivalent area.
    (G) The required steam relieving capacity, in pounds per hour, of the pressure relieving device or devices on a boiler shall be the greater of that determined by dividing the maximum output in Btu at the boiler nozzle obtained by the firing of any fuel for which the unit is installed by 1,000 or shall be determined on the basis of pounds of steam generated per hour per square foot of boiler heating surface as given in §65.615, Exhibit 7. For cast iron boilers the minimum valve capacity shall be determined by the maximum output method.
    (H) In every case, the pressure relief valve capacity for each boiler with a single pressure relief valve shall be such that, with the fuel burning equipment installed and operated at maximum capacity, the pressure cannot rise more than 10% above the MAWP. When more than one pressure relief valve is used, the overpressure shall be limited to 10% above the set pressure of the highest set valve.
    (I) Pressure relief valve piping. No valve shall be placed between the pressure relief valve and the boiler or on the discharge pipe between the pressure relief valve and the drain. When a discharge pipe is used, it shall be full size and fitted with an open drain to prevent water from lodging in the upper part of the pressure relief valve or in the discharge pipe. When an elbow is placed on the pressure relief valve discharge pipe, it shall be located close to the valve outlet. The discharge pipe shall be securely anchored and supported, independent of the valve. Mufflers shall not be used on hot water heating boilers.
    (J) Pressure relief valves and safety valves shall be installed on the boiler with spindles positioned vertically. The opening or connection between the boiler and any pressure relief valve or safety valve shall have at least the area of the valve inlet.
  (2) Makeup water connections.
    (A) Makeup water or water treatment shall be introduced into a boiler through the return piping system or through an independent makeup water connection, which does not discharge against parts of the boiler exposed to direct radiant heat from the fire. Makeup water or water treatment shall not be introduced through openings or connections provided for inspection or cleaning, pressure relief valve, pressure gage, or temperature gage.
    (B) Makeup water pipe shall be provided with a check valve near the boiler and a stop valve or cock between the check valve and the boiler, or between the check valve and the piping system.
  (3) Low-water fuel cutoffs and water feeding devices.
    (A) All automatically fired hot water heating boilers shall have an automatic low-water fuel cutoff that has been designed for hot water service, and it shall be so located as to automatically cut off the fuel supply when the surface of the water falls to a level below the normal waterline established.
    (B) The MAWP of all low water fuel cutoff and flow sensing devices shall be set at or above the boiler stamped MAWP.
    (C) When low-water fuel cutoff and feedwater pump controls are combined in a single device, an additional separate low-water fuel cutoff shall be installed. The additional control shall be wired in series electrically with the existing low-water fuel cutoff.
    (D) When a low-water fuel cutoff is housed in either the water column or a separate chamber it shall be provided with a blowdown pipe and valve not less than 3/4 inch nominal pipe size (20 mm). The arrangement shall be such that when the water column is blown down, the water level in it will be lowered sufficiently to activate the low-water fuel cutoff device.
    (E) As there is no normal water line to be maintained in a hot water heating boiler, any location of the low-water fuel cutoff above the lowest safe water level established by the boiler manufacturer is satisfactory.
    (F) All automatically fired hot water heating boilers, when installed in a forced circulation system and not under continuous attendance, shall be equipped in the manner described in this subsection. A coil-type boiler or a water-tube boiler requiring forced circulation to prevent overheating of the coils or tubes shall have a flow sensing device which is listed by a nationally recognized testing agency to prevent burner operation at a flow rate inadequate to protect the boiler unit against overheating.
    (G) If a water feed device is utilized, it shall be constructed to prevent feedwater from entering the boiler through the water column or separate chamber of the low-water fuel cutoff.
  (4) Pressure and Temperature gages.
    (A) Each hot water heating boiler shall have a pressure or altitude gage connected to it or to its flow connection, which cannot be shut off from the boiler except by a cock with tee or lever handle placed in a pipe near the gage. The handle of the cock shall be parallel to the pipe in which it is located when the cock is open.
    (B) The scale on the dial of the pressure or altitude gage shall be graduated to not less than 1 1/2 nor more than 3 1/2 times the pressure at which the pressure relief valve is set. The gage shall be provided with effective stops for the indicating pointer at the zero point and at the maximum pressure point.
    (C) Piping and tubing for pressure or altitude gage connections shall be of nonferrous metal when smaller than 1 inch nominal pipe size (25 mm).
    (D) Each hot water heating boiler shall have a thermometer or temperature gage located and connected, that it shall be readable, and shall be located so that it shall at all times indicate the temperature of the water in the boiler at or near the outlet. If placed on the outlet piping, it must be located between the stop valve and the boiler.
  (5) Stop valves.
    (A) Stop valves shall be located at an accessible point in the supply and return pipe connections near the boiler nozzle of a single hot water heating boiler installation to permit draining the boiler without emptying the system.
    (B) When the boiler is located above the system and can be drained without draining the system, stop valves may be eliminated.
Cont'd...
(C) Type of stop valve. When stop valves over two inches in size are used, they shall be of the outside screw-and-yoke rising stem type or of such other type as to indicate at a distance whether it is closed or open by the position of its stem or other operating mechanism. The wheel may be carried either on the yoke or attached to the stem. If the valve is of the plug cock type, it shall be fitted with a slow opening mechanism and an indicating device and the plug shall be held in place by a guard or gland.
  (6) Drain valve.
    (A) Each hot water heating boiler shall have one or more drain connections, fitted with valves or cocks connecting to the lowest water containing spaces. The minimum size of the drain piping, valves, and cocks shall be 3/4 inch nominal pipe size (20 mm). The discharge piping shall be full size to the point of discharge. When the blowoff connection is located at the lowest water containing space, a separate drain connection is not required.
    (B) Minimum pressure rating. The minimum pressure rating of valves and cocks used for blowoff or drain purposes shall be at least equal to the pressure stamped on the boiler, but in no case less than 30 psig (207 kilopascals). The temperature rating of such valves and cocks shall not be less than 250 degrees Fahrenheit (121 degrees Celsius).
  (7) Provisions for thermal expansion.
    (A) Heating systems with open expansion tank- An indoor overflow from the upper portion of the expansion tank shall be provided in addition to an open vent, the indoor overflow to be carried within the building to a suitable plumbing fixture or basement.
    (B) Closed heating system.
      (i) If the system is of closed type, an airtight tank or other suitable air cushion that is consistent with the volume and capacity of the system shall be installed.
      (ii) If the system is designed for a working pressure of 30 psig (207 kilopascals) or less, the tank shall be suitably designed for a minimum hydrostatic pressure of 75 psig (520 kilopascals).
      (iii) Expansion tanks for systems designed to operate above 30 psig (207 kilopascals) shall be constructed in accordance with the ASME Code, Section VIII, Division 1, or Section X, and the pressure and temperature ratings of the tank shall be equal to or greater than the pressure and temperature ratings of the system pressure. A pressure relief valve shall be installed with a set pressure at or below the MAWP of the expansion tank. Alternately the boiler pressure relief valve may be used provided the expansion tank's MAWP is equal to or greater than the set pressure of the pressure relief valve.
      (iv) Provisions shall be made for draining the tank without emptying the system, except for pre-pressurized tanks.
      (v) If the expansion tank was originally equipped with a sight glass, the sight glass and sight glass valves shall be in working condition at all times, and the water level shall be maintained as per the manufacturer's recommendations.
  (8) Piping, Fittings and Valves.
    (A) All piping, fittings and valves on the boiler supply and return lines shall have a pressure rating equal to or greater than the MAWP of the boiler and a temperature rating of no less than 250 degrees Fahrenheit (121 degrees Celsius).
    (B) All piping, fittings and valves other than the boiler supply and return lines shall have a minimum pressure and temperature rating equal to or greater than the maximum expected pressure and temperature that may be reached.
(c) Hot Water Supply Boilers.
  (1) Pressure relief valves.
    (A) Each hot water supply boiler shall have at least one pressure relief valve, of the automatic reseating type, identified with the ASME certification mark with the "V" or "HV" designators, and set to relieve at or below the MAWP of the boiler.
    (B) When more than one pressure relief valve is used on a hot water supply boiler, the additional valve or valves shall be officially rated and may have a set pressure within a range not to exceed 6 psig (42 kilopascals) above the MAWP of the boiler up to and including 60 psig (414 kilopascals), and 5.0% for those having a MAWP exceeding 60 psig (414 kilopascals).
    (C) Pressure relief valves shall be spring loaded. Pressure relief valves shall be set and sealed so that they cannot be reset without breaking the seal. A body drain connection below seat level shall be provided. For valves exceeding 2 1/2 inch nominal pipe size (65 mm), the drain hole or holes shall be tapped not less than 3/8 inch nominal pipe size (10 mm). For valves of 2 1/2 inch nominal pipe size (65 mm) or less, the drain hole shall not be less than 1/4 inch (6 mm) diameter.
    (D) Each pressure relief valve shall have a substantial lifting device which will positively lift the disk from its seat at least 1/16 inch (1.6 mm) when there is no pressure on the boiler.
    (E) Seats and disks of pressure relief valves shall be made of a suitable material to resist corrosion. No materials likely to fail due to deterioration or vulcanization, when subjected to saturated steam temperature corresponding to capacity test pressure, shall be used for any part.
    (F) No pressure relief valve shall be smaller than 3/4 inch nominal pipe size (20 mm) nor larger than 4 1/2 inch nominal pipe size (115 mm) except that boilers having a heat input not greater than 15,000 Btu/hr (4.4 kilowatts) may be equipped with a rated pressure relief valve of 1/2 inch nominal pipe size (15 mm). The inlet opening shall have an inside diameter approximately equal to, or greater than, the seat diameter. In no case shall the minimum opening through any part of the valve be less than 1/4 inch (6 mm) diameter or its equivalent area.
    (G) The required steam relieving capacity, in pounds per hour, of the pressure relieving device or devices on a boiler shall be the greater of that determined by dividing the maximum output in Btu at the boiler nozzle obtained by the firing of any fuel for which the unit is installed by 1,000, or shall be determined on the basis of pounds of steam generated per hour per square foot of boiler heating surface as given in §65.615, Exhibit 7. For cast iron boilers, the minimum valve capacity shall be determined by the maximum output method.
    (H) In every case, the pressure relief valve capacity for each boiler with a single pressure relief valve shall be such that, with the fuel burning equipment installed and operated at maximum capacity, the pressure cannot rise more than 10% above the MAWP. When more than one pressure relief valve is used, the overpressure shall be limited to 10% above the set pressure of the highest set valve.
    (I) Pressure relief valve piping. No valve shall be placed between the pressure relief valve and the boiler nor on the discharge pipe between the pressure relief valve and the drain. When a discharge pipe is used, it shall be full size and fitted with an open drain to prevent water from lodging in the upper part of the pressure relief valve or in the discharge pipe. When an elbow is placed on the pressure relief valve discharge pipe, it shall be located close to the valve outlet. The discharge pipe shall be securely anchored and supported, independent of the valve. Mufflers shall not be used on hot water supply boilers.
    (J) Pressure relief valves and safety valves shall be installed on the boiler with spindles positioned vertically. The opening or connection between the boiler and any pressure relief valve or safety valve shall have at least the area of the valve inlet.
  (2) Makeup water connections.
    (A) Makeup water or water treatment shall be introduced into a boiler through the return piping system or through an independent makeup water connection which does not discharge against parts of the boiler exposed to direct radiant heat from the fire. Makeup water or water treatment shall not be introduced through openings or connections provided for inspection or cleaning, pressure relief valve, pressure gage, or temperature gage.
    (B) Makeup water pipe shall be provided with a check valve near the boiler and a stop valve or cock between the check valve and the boiler or between the check valve and the piping system.
  (3) Low-water fuel cutoffs and water feeding devices.
    (A) All automatically fired hot water supply boilers shall have an automatic low-water fuel cutoff that has been designed for hot water service, and it shall be so located as to automatically cut off the fuel supply when the surface of the water falls to a level below the normal waterline established.
    (B) The MAWP of all low water fuel cutoff and flow sensing devices shall be set at or above the boiler stamped MAWP.
    (C) When low-water fuel cutoff and feedwater pump controls are combined in a single device, an additional separate low-water fuel cutoff shall be installed. The additional control shall be wired in series electrically with the existing low-water fuel cutoff.
Cont'd...
(D) When a low-water fuel cutoff is housed in either the water column or a separate chamber it shall be provided with a blowdown pipe and valve not less than 3/4 inch nominal pipe size (20 mm). The arrangement shall be such that when the water column is blown down, the water level in it will be lowered sufficiently to activate the low-water fuel cutoff device.
    (E) As there is no normal water line to be maintained in a hot water supply boiler, any location of the low-water fuel cutoff above the lowest safe water level established by the boiler manufacturer is satisfactory.
    (F) All automatically fired hot water heating boilers, when installed in a forced circulation system and not under continuous attendance, shall be equipped in the manner described in this subsection. A coil-type boiler or a water-tube boiler requiring forced circulation to prevent overheating of the coils or tubes shall have a flow sensing device which is listed by a nationally recognized testing agency to prevent burner operation at a flow rate inadequate to protect the boiler unit against overheating.
    (G) If a water feed device is utilized, it shall be constructed to prevent feedwater from entering the boiler through the water column or separate chamber of the low-water fuel cutoff.
  (4) Pressure and Temperature gages.
    (A) Each hot water supply boiler shall have a pressure or altitude gage connected to it or to its flow connection which cannot be shut off from the boiler except by a cock with tee or lever handle placed in a pipe near the gage. The handle of the cock shall be parallel to the pipe in which it is located when the cock is open.
    (B) The scale on the dial of the pressure or altitude gage shall be graduated to not less than 1 1/2 nor more than 3 1/2 times the pressure at which the pressure relief valve is set. The gage shall be provided with effective stops for the indicating pointer at the zero point and at the maximum pressure point.
    (C) Piping and tubing for pressure or altitude gage connections shall be of nonferrous metal when smaller than 1 inch nominal pipe size (25 mm).
    (D) Each hot water supply boiler shall have a thermometer or temperature gage located and connected so that it shall be readable, and shall be located so that it shall at all times indicate the temperature of the water in the boiler at or near the outlet. If placed on the outlet piping, it must be located between the stop valve and the boiler.
  (5) Stop valves.
    (A) Stop valves shall be located at an accessible point in the supply and return pipe connections near the boiler nozzle of a single hot water supply boiler installation to permit draining the boiler without emptying the system.
    (B) When the boiler is located above the system and can be drained without draining the system, stop valves may be eliminated.
    (C) Type of stop valve. When stop valves over two inches in size are used, they shall be of the outside screw-and-yoke rising stem type or of such other type as to indicate at a distance whether it is closed or open by the position of its stem or other operating mechanism. The wheel may be carried either on the yoke or attached to the stem. If the valve is of the plug cock type, it shall be fitted with a slow opening mechanism and an indicating device and the plug shall be held in place by a guard or gland.
  (6) Drain valve.
    (A) Each hot water supply boiler shall have one or more drain connections, fitted with valves or cocks connecting to the lowest water containing spaces. The minimum size of the drain piping, valves, and cocks shall be 3/4 inch nominal pipe size (20 mm). The discharge piping shall be full size to the point of discharge. When the blowoff connection is located at the lowest water containing space, a separate drain connection is not required.
    (B) Minimum pressure rating. The minimum pressure rating of valves and cocks used for blowoff or drain purposes shall be at least equal to the pressure stamped on the boiler, but in no case less than 30 psig (207 kilopascals). The temperature rating of such valves and cocks shall not be less than 250 degrees Fahrenheit (121 degrees Celsius).
  (7) Provisions for thermal expansion.
    (A) If a system is equipped with a check valve or pressure reducing valve in the cold water inlet line, consideration should be given to the installation of an airtight expansion tank or other suitable air cushion. Otherwise, due to the thermal expansion of the water, the pressure relief valve may lift periodically.
    (B) If an expansion tank is provided, it shall be constructed in accordance with the ASME Code, Section VIII, Division 1 or Section X, and the pressure and temperature ratings of the tank shall be equal to or greater than the pressure and temperature ratings of the system pressure. Except for pre-pressurized tanks, which should be installed on the cold water side, provisions shall be made for draining the tank without emptying the system.
    (C) If the expansion tank was originally equipped with a sight glass, the sight glass and sight glass valves shall be in working condition at all times, and the water level shall be maintained as per the manufacturer's recommendations.
  (8) Piping, Fittings and Valves.
    (A) All piping, fittings and valves on the boiler supply and return lines shall have a pressure rating equal to or greater than the MAWP of the boiler and a temperature rating of no less than 250 degrees Fahrenheit (121 degrees Celsius).
    (B) All piping, fittings and valves other than the boiler supply and return lines shall have a minimum pressure and temperature rating equal to or greater than the maximum expected pressure and temperature that may be reached.
(d) Potable Water Heaters (ASME Code HLW).
  (1) Pressure relief valves.
    (A) Potable water heaters (tank type) shall have at least one officially rated temperature and pressure relief valve, or one officially rated pressure relief valve, set to relieve at or below the maximum allowable pressure of the heater. No pressure relief valve shall be smaller than 3/4 inch nominal pipe size (20 mm). The valve (s) shall be marked with the ASME Code Symbol "V" or "HV". At no time shall the temperature probe of the temperature and pressure relief valve be removed or modified.
    (B) The pressure relief valve shall have a capacity equal to or exceeding the rated burner input of the heater. The relieving capacity for electric water heaters shall be 3,500 Btu/hr (1.0 kilowatts) per kilowatt of input.
    (C) The ASME Btu rating on the valve shall be used to determine the relieving capacity.
    (D) Pressure relief valves shall be connected directly to the heater within the top 6 inches of the tank.
    (E) Pressure relief valves may be installed vertically or horizontally. The center line of the horizontal connection shall be no lower than 4 inches from the top of the shell.
    (F) Pressure relief valves shall not be connected to an internal pipe in the heater, or to a cold water feed line connected to the heater.
    (G) Pressure relief valve piping. No valve shall be placed between the pressure relief valve and the boiler nor on the discharge pipe between the pressure relief valve and the drain. When a discharge pipe is used, it shall be full size and fitted with an open drain to prevent water from lodging in the upper part of the pressure relief valve or in the discharge pipe. When an elbow is placed on the pressure relief valve discharge pipe, it shall be located close to the valve outlet. The discharge pipe shall be securely anchored and supported, independent of the valve. Mufflers shall not be used on potable water heaters.
  (2) Water supply.
    (A) Water supply shall be introduced into a water heater through an independent water supply connection. Water shall not be introduced through openings or connections provided for cleaning, pressure relief valves, drains, pressure gage or temperature gage.
    (B) If the water supply pressure to a hot water heater exceeds 75% of the set pressure of the pressure relief valve, a pressure reducing valve is required.
  (3) Flow sensing device.
    (A) All automatically fired potable water heaters, when installed in a forced circulation system and not under continuous attendance, shall be equipped in the manner described in this subsection. A coil-type boiler or a water-tube boiler requiring forced circulation to prevent overheating of the coils or tubes shall have a flow sensing device which is listed by a nationally recognized testing agency to prevent burner operation at a flow rate inadequate to protect the boiler unit against overheating.
    (B) The MAWP of all flow sensing devices shall be set at or above the boiler stamped MAWP.
  (4) Gages.
Cont'd...
(A) Temperature gages. Each hot water heater shall have a thermometer located and connected at or near the outlet that is readable. The thermometer shall at all times indicate the temperatures of the water in the hot water heater. If placed on the outlet piping, it must be located between the stop valve and the boiler.
    (B) Pressure gages. Each hot water heater that is of the coil type or water tube shall have a pressure gage located as close to the boiler as possible that is graduated to not less than 1 1/2 or more than 3 1/2 times the pressure at which the pressure relief valve is set.
  (5) Stop valves. Stop valves should be placed in the supply and discharge pipe connections of the hot water heater installation to permit draining the heater without emptying the system.
  (6) Drain valves. Each hot water heater shall have a bottom drain pipe connection fitted with a valve or cock connected to the lowest water space practical. The minimum size bottom drain shall be 3/4 inch nominal pipe size (20 mm).
  (7) Provisions for thermal expansion.
    (A) If a system is equipped with a check valve or pressure reducing valve in the cold water inlet line, consideration should be given to the installation of an airtight expansion tank or other suitable air cushion. Otherwise, due to the thermal expansion of the water, the pressure relief valve may lift periodically.
    (B) If an expansion tank is provided, it shall be constructed in accordance with the ASME Code, Section VIII, Division 1 or Section X, and the pressure and temperature ratings of the tank shall be equal to or greater than the pressure and temperature ratings of the system pressure.
    (C) Except for pre-pressurized tanks, which should be installed on the cold water side, provisions shall be made for draining the tank without emptying the system.
    (D) If the expansion tank was originally equipped with a sight glass, the sight glass and sight glass valves shall be in working condition at all times, and the water level shall be maintained as per the manufacturer's recommendations.
  (8) Piping, Fittings and Valves.
    (A) All piping, fittings and valves on the boiler supply and return lines shall have a pressure rating equal to or greater than the MAWP of the boiler and a temperature rating of no less than 210 degrees Fahrenheit (99 degrees Celsius).
    (B) All piping, fittings and valves other than the boiler supply and return lines shall have a minimum pressure and temperature rating equal to or greater than the maximum expected pressure and temperature that may be reached.

Source Note: The provisions of this §65.611 adopted to be effective June 15, 2015, 40 TexReg 3121; amended to be effective February 15, 2016, 41 TexReg 795; amended to be effective September 1, 2018, 43 TexReg 5361