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Pressure Oscillation Test


randynavarro
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OK. Quit holding out on me.

According to a local water heater replacement company, this is some sort of simple test they do to determine if the plumbing system is closed or open. This will determine the need for an expansion tank.

If it's simple it would be worthy of incorporation in my routine.

If only someone knew what it was!

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Originally posted by randynavarro

Anybody know how to do one?

Supposably, (sorry, been with my kids too much), supposedly one can determine if a plumbing system is closed or open.

Pressure oscillation test...

Is that like the day after you ate too many burrito's?

Around here if there is no antibackflow on the water main then it is open... I would guess if it is to determine a need for an expansion tank it would involve putting a shrader valve on the system somewhere and adding pressure to see if it backs down on it's own or not.

Note: This is a completely half ass GUESS, and I should not be confused in any way with someone who is even remotely educated in this area.

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I think you are close to the mark. I would think the local water utility would know if you gave them home's address or date of construction (or when the water service line was last replaced, for an older home), if a backflow preventer is installed on the service line.

Don't know how to do the test, though. Have you called a local plumber?

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Originally posted by msteger

I think you are close to the mark. I would think the local water utility would know if you gave them home's address or date of construction (or when the water service line was last replaced, for an older home), if a backflow preventer is installed on the service line.

Don't know how to do the test, though. Have you called a local plumber?

I talked to a plumber yesterday and asked him about the backflow issue. He said these have been pretty standard at least 10 years in the meters.

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Okay. Just got off the phone with a water heater tech. from one of the big water heater outfits here in Seattle. . .

Here's how they do it:

Method A - not completely reliable

1) stick a pressure gage on the drain cock at the bottom of the water heater

2) run a faucet for 30 seconds or so

3) If the pressure returns slowly, then there's likely a reducing valve - the system is closed

4) If the pressure bounces back semi-fast and "bounces", the system is open

5) if the pressure bounces back hard and sticks, the system is closed.

Method B - Applied Heat method - very reliable

1) stick a gage on the drain cock or hose bibb

2) fire the water heater-(turn up the t-stat or run a hot fixture for 5-10 minutes)

3) turn the fixture off

4) as water heats, the pressure will rise. If it does, the system is closed

5) if the pressure doesn't rise as the water heats, the system is open

These tests sound pretty basic and can be incorporated in to a typical inspection routine, in my opinion. I'm gonna dink with it the next few times out and see if its practical.

As Scott has already alluded, if you see a pressure reducing valve or the check valve at the meter, then you know the system is closed--an expansion tank is required.

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