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How does one test a back flow check valve that sits between the city water supply mains and my business fire supression system?
 

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As a former plant manager I've delt with some of this stuff. Especially the NFPA 25 tests. Some things get tested every 1, 2, 3, 5, 10 yrs. You should get about a 35 pg report annually from your sprinkler contractor.

Every system is a bit different. I'll try to give you a generic answer. Your valve is either in your riser or in a pit outside. (***Caution - there can be deadly methane in the pit*** There are strict regulations for working in it.) Open your inspectors test valve to the outside of the bldg and let the water flow. Then shut it off. Shut off your supply from the city. Then if the check valve is working properly the cavity in the valve will have no pressure or water after you drain its chamber. You'll open a valve milled into the side of the chamber to drain it. There also may be a pressure gauge milled into the valve too or on an adjacent smaller pipe that in some way connected to the check valve chamber. Hopefully the water will stop coming from the drain.

Some valves actually have an inspection cover you can remove to see the flapper door closed on the plant side or to see if the gasket is leaking. If not there are various bypasses around the valves with pressure gauges that you can determine the back flow / head pressure from the plant side. You may have to introduce addl air to to get the plant side up to the spec pressure or its done with a small fire pump upon opening the inspectors test valve before shutting off the city water.

These sprinkler systems /componants are usually well built. If the valve is leaking, many times its the heavy black gasket that the flapper door closes against. They're easily replaced. Another thing is if you have operating inconsistancies across the gauges they need to be replaced to get proper readings. They are mandated to be replaced every 10 years. The date of mfg is on the dial face. Go to the NFPA site and get the NFPA 25 reference book. It has some specs on what's supposed to happen overall.

Every system is unique with its own valves, bypasses, gauges etc. You should be working with a sprinkler contractor annually.

By the way, why do you ask ?

Addl - Hmmmm....let me guess ? The Fire Captain came in asking for the inspection report. You can't inspect it in house without the proper certifications. The sprinkler guy will give you a report and / or send it to the Capt. noted on your violation notice.

If you haven't been working with a sprinkler contractor the initial annual survey can be expensive, but in future years they run right through it and its less costly.
 
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