How to test a RPZ backflow preventer

In this video I tested two RPZ backflow preventers for a dentist office. One of them was easy, the other not so much. Thanks for watching!
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[@danielg.9578]

From my understanding, Check #2 PSID is the actual Pressure Drop across Check #2. You would put High hose on TC #3 and Low Hose on TC #4 for that pressure differential measurement.

[@joninnet]

Reverse the hoses on your rig. The bend on the other end of your high hose will allow you to avoid that half inch water line over the test cock.

[@Invictusxiv]

Something I’ve noticed is nobody talks about the buffer. If you recorded it, how did you? I’m curious about the relevance of it.

[@andy_plumbs]

The buffer?

[@Invictusxiv]

@@andy_plumbs Some departments have on their test sheets "buffer PSI" as it's main purpose is to see how much of pressure fluxuation there is, usually it has to be more than 3.0 psi from what I understand. Do you check the buffer on your tests? I have to in mystate/county.

[@andy_plumbs]

@@Invictusxiv nope, never heard of it.

[@JimmyBackflow]

The differential across the second check valve differs from the differential pressure across the first check valve. Also, to backpressure the second check valve, the high control valve must be opened to introduce high pressure to the backside of the second check valve. Bad installation, no drain for catastrophic discharge. There are many problems with this video.

[@andy_plumbs]

Are you saying the way I tested it was incorrect? I agree that the RP should be dumping to a drain but I didn’t plumb the building.

[@JimmyBackflow]

@@andy_plumbs To measure the differential pressure across the first check valve, connect the high-pressure hose to TC#2 and the low-pressure hose to TC#3, bleed out the air and take the reading. To backpressure the second check valve with the hoses still connected to TC#2 and TC#3, bleed the air out of the vent hose by opening the low control valve and connecting the vent hose to TC#4. Open the high control valve one complete turn and observe the relief valve. If there is no discharge, the second check valve is drip-tight with backpressure. To validate that backpressure was introduced behind the second check valve and not going downstream, close TC#2 and observe the gauge. If holding steady, the backpressure of the second check valve is confirmed, and the backflow preventer test was conducted when in a static state. To trigger the relief valve, open the low control valve one-quarter turn and observe the first drip. To test the DP across the second check valve, close TCs and remove hoses. Next, connect the high-pressure hose to TC#3 and the low-pressure hose to TC#4. Bleed and take the reading. It should be one psid or greater. I refer you to videos on TH-cam at jimmybakcflow.com. Also, the AWWA M14 manual has several test procedures, including the one I described. Testing is easy, but not done correctly causes concerns.

[@andy_plumbs]

@@JimmyBackflow the procedure you’re describing is similar to how DC’s are tested, but I’ve never disconnected my hoses and jumped test cocks on a RP. I’ve always used the ASSE field test procedure book and it doesn’t mention anything of jumping test cocks either.

[@JimmyBackflow]

@@andy_plumbs To measure the DP across the RP second check valve, you must measure the pressure at TC#3 and TC#4. You will not see the steps described for measuring the DP across the second check valve because most test procedures and authorities do not require them. The problem occurs when testers fill out the form and put the DP of the first check valve in the second check valve box. This is a big problem in the industry because trainers do not explain how to measure the DP across the second check valve. If you want to measure the DP across the RP second check valve, do it correctly. If not, leave it blank. If you watch my videos, you will have a good understanding on how to test backflow preventers. The procedure is used through the NE States, NY, PA, and NJ and is outlined in the AWWA M14 Cross-connection Control Manual. Also, NEWWA provides a certification program for testing backflow preventers; a written copy of the test procedure is available.