Use of a Backflow Preventer in Boiler Applications


The Department of Community Affairs (DCA) has been receiving many calls pertaining to the requirement
for a check valve in the domestic water supply for the boiler water makeup, in addition to the backflow preventer as required by the Plumbing Subcode. The check valve violation is being issued by an insurance company’s inspector or by an inspector from the New Jersey Department of Labor and Workforce Development, Bureau of Boiler and Pressure Vessel Compliance (BB&PVC.)

A check valve and stop valve or cock are required by the American Society of Mechanical Engineers (ASME) standard, which is referenced through N.J.A.C. 12:90, Boilers, Pressure Vessels, and Refrigeration Compliance Regulations. ASME Section IV, HG-705(a) and (b), states that a check valve must be installed in the boiler water makeup system supply line. Also, a stop valve or cock must be installed between the heck valve and the boiler. The ASME standard is enforced by the BB&PVC.

The BB&PVC has determined that a standard backflow preventer, as required by the Plumbing Subcode, would not prevent the backflow of water from a boiler into the potable water system due to the fact that the seats on the backflow preventer check valves would not be able to withstand the high-temperature hot water from the boiler should there be a break in the water supply system which would cause a back siphonage from the boiler into the potable water system. Typically, backflow preventers are rated at 140 degrees to 180 degrees Fahrenheit. Check valves are rated at 250 degrees Fahrenheit. The ratings of the backflow preventers and check valves were verified through the manufacturer of the devices.

Also, with the use of a reduced-pressure backflow preventer assembly, should the check valve in the backflow preventer fail due to the high-temperature water backflow from the boiler, the backflow would discharge through the relief vent, which puts the boiler at risk for a dry-firing condition and could result in a catastrophic failure or a boiler explosion. This would also apply to a double check valve assembly should the assembly check valves fail due to the high-temperature water which would backflow into the potable water supply.

DCA-licensed plumbing subcode officials are to ensure that the proper required backflow preventer is
installed on the potable water supply for a boiler water makeup, per the Plumbing Subcode. The plumbing
subcode official should not approve the installation unless the proper additional check valve and stop valve or cock are installed in the boiler water makeup supply, as required by N.J.A.C. 12:90 through ASME, which is enforced by the BB&PVC. During the plan review stage and during your inspection of a boiler which would be regulated by the BB&PVC, you should bring to the attention of the contractor that an additional check valve and stop valve or cock will be required per the N.J.A.C. 12:90 regulations in
order to pass the BB&PVC inspection.

If you notice any problems, please report them to Milton Washington, Chief of the BB&PVC, at (609) 292-
2921.


To help DCA inspectors, the following is the text of the scope of the BB&PVC regulations, which are found
at N.J.A.C. 12:90-4:

N.J.A.C. 12:90-4.1(b) This subchapter shall not apply to:

  1. Steam boilers having adequate relief devices set to discharge at a pressure not greater than 15 psig when such boilers serve buildings of less than six dwelling units or other dwellings with accommodations for less than 25 persons;
  2. Hot-water boilers having relief devices set to discharge at a pressure not greater than 160 psig
    and hot-water boilers limited to temperatures not exceeding 250 degrees Fahrenheit when such
    boilers serve buildings of less than six dwelling units or other dwellings with accommodations for
    less than 25 persons;
  3. Any steam or hot-water boiler having less than 10 square feet of surface;
  4. Any steam or hot-water boiler having a heat input of less than 10 kilowatts or less than 40,000 BTU
    per hour;
  5. Any steam or hot-water boiler under the jurisdiction and control of the United States Government when actively regulated by a federal agency; and
  6. Any steam or hot-water boiler used solely for the propulsion of a motor vehicle regulated by the
    Motor Vehicle Act, Title 39 of the Revised Statutes.

As stated above, these regulations do not apply to boilers in buildings with fewer than six dwelling units.

Contact:

Thomas C. Pitcherello
Code Assistance Unit
(609) 984-7609

Source:
Construction Code Communicator, Volume 19, Number 1, Spring 2007 (PDF)

 

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