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Called out for a possible leak today, damp section of insulationin attic and water stains on the ceiling. 2007 house piped overhead in pex b. Checked all connections in the attic, couldn't find anything. So we decided to run pressure test: shut off every stop, checked every shower/tub, and put a gauge on the washer outlet. The meter isn't perceptably moving. We shut it off. The gauge drops from 90 psi to 0 in about 45 seconds. Turn meter back on, it spins then stops. Doesn't move for 5 minutes. Try the test again, gauge still drops.

My journey and service manager (master) were stumped. Any ideas what it could be?

The water in the attic turn out to be bad flashing when the roof got redone. We found that by hosing down the roof.
 

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So you found the leak that was due to a roof leak and now your question is why you have pressure drop? Where are the pictures?

Might be a faulty gauge, try another.
 

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So you found the leak that was due to a roof leak and now your question is why you have pressure drop? Where are the pictures?

Might be a faulty gauge, try another.
How would a faulty gauge "lose" pressure without leaking water? Show the wrong pressure yes. My guess is the old favorite for running water, a toilet.

I would look in the waste piping and see if you've got water coming down the drain.

Or put dye in the toilet tank and see if it ends up in the bowl.
 

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My guess is the old favorite for running water, a toilet.
I suppose it's possible. We had all the stops shut off though. One could have been bad.

now your question is why you have pressure drop?
Yes. What would cause the pressure in the house to drop to zero within a minute, but not cause the meter to spin at all when the water is on? I would think a big enough leak to cause that kind of a pressure drop would show up at the meter.
 

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The only thing that will move the meter is
Its either one of the toilets moving water or a water softener moving water through it
or the t+p valve....

I think you already found the problem you were looking for with the leaking boot on the roof...
but also if you do not INSULATE the pex pipe going through the attic with aramaflex, it will
weep like a baby..... if the lines are not insulated they will condensate and drip......
 

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Discussion Starter #9
Just asking, did you guys rule out the water service?
I'm not quite sure what you mean by this. Could you clarify?

Sprinkler valve or float style pool filler
Turned off the pool filler. Sprinkler RPZ appeared to be off.

We explained to the homeowner what was happening. She was more concerned that the roofers told her there was no leak in the flashing and then we found one. She is a loyal repeat customer of ours, so I'm sure we'll get a call if something else points to a leak.

Now that I think about it, we never did check the T/P valves. They have 2 tankless Rinnai units and a recirc loop. Do tankless normally pop T/P valves?

Thanks for bearing with me. I've done a fair bit of "maintenance plumbing," but I am still a 1st year when it comes down to it.
 

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............Thanks for bearing with me. I've done a fair bit of "maintenance plumbing," but I am still a 1st year when it comes down to it.
We love to help fellow plumbers ;)

I wouldn't call one year a fair bit of anything though. You'll see new things all the time for decades to come.
 

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I'm not quite sure what you mean by this. Could you clarify?

Turned off the pool filler. Sprinkler RPZ appeared to be off.

We explained to the homeowner what was happening. She was more concerned that the roofers told her there was no leak in the flashing and then we found one. She is a loyal repeat customer of ours, so I'm sure we'll get a call if something else points to a leak.

Now that I think about it, we never did check the T/P valves. They have 2 tankless Rinnai units and a recirc loop. Do tankless normally pop T/P valves?................
If you just simply shut the main valve than pressure could be going back to the city line/well pump. RPZ appeared to be off but valve could be leaking by. Just check to see if the T&P's are leaking, they shouldn't be or I think you would have noticed.

Water doesn't compress so if there's a leak and there's no air in the system it will drop fast. But...

If you got air in the system, which I am sure there is if you're hooking up a gauge in line than the pressure may drop from the air cooling because it will compress. In which case just repressurize it a second time and see if it drops then. If you do this several times and it repeatedly drops than you have a leak somewhere.

If you're really intent on finding the "leak" I suggest you air test so you can hear the leak.
 

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Does it drop all the way to zero?
 

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Could there be a heating system/loop that's taking the water?
 

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If, as you say, the rotor on the meter doesn't move when everything is shut off (and there is no noticeable increase in the water bill), then what's the big deal.
I was thinking the same thing but I assume the homeowner is spooked now that they've had one leak and is worried there may be water damage in a wall somewhere.
 
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Called out for a possible leak today, damp section of insulationin attic and water stains on the ceiling. 2007 house piped overhead in pex b. Checked all connections in the attic, couldn't find anything. So we decided to run pressure test: shut off every stop, checked every shower/tub, and put a gauge on the washer outlet. The meter isn't perceptably moving. We shut it off. The gauge drops from 90 psi to 0 in about 45 seconds. Turn meter back on, it spins then stops. Doesn't move for 5 minutes. Try the test again, gauge still drops.

My journey and service manager (master) were stumped. Any ideas what it could be?

The water in the attic turn out to be bad flashing when the roof got redone. We found that by hosing down the roof.
You did mention that you shut all the stops, but if there is a bad washer on even one of them you could still be leaking by and dropping pressure. Especially through a toilet fill valve.
 

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Discussion Starter #17
Thanks for the replies. The HO wasn't terribly worried about and said they would keep an eye on the water bill. Neither I, my journey, or our master was convinced there was a leak in the house. I was looking for info on other stuff to check should I run j to a similar situation in the future and do have a concerned customer on my hands.
 

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Thanks for the replies. The HO wasn't terribly worried about and said they would keep an eye on the water bill. Neither I, my journey, or our master was convinced there was a leak in the house. I was looking for info on other stuff to check should I run j to a similar situation in the future and do have a concerned customer on my hands.
it doesnt take much water loss to lower the pressure, when the gauge reads top pressure , go to a faucet with a plastic cup and release water till the gauge reads zero, then you will know the small amount of water it took to lower the pressure to give the home owner an idea of the amount of water your talking about..
 

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Is it possible the meter isn’t registering a tiny leak but your pressure gauge is showing the leak ?

If so, it might be best to wait for the leak to get worse to help locate but in some situations that’s not the most desirable approach. If it’s a leak under a concrete foundation I like to isolate either cold or hot and then start locating.
 

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Is it possible the meter isn’t registering a tiny leak but your pressure gauge is showing the leak ?

If so, it might be best to wait for the leak to get worse to help locate but in some situations that’s not the most desirable approach. If it’s a leak under a concrete foundation I like to isolate either cold or hot and then start locating.
I had an issue recently with a radiant floor system, it was for a friend, he did all the pex loops and its been in service a few years no issue, till this year he was getting air bound one 1 floor...it ended up being a bad loop with a leak, no water was seen, but it was sucking air, after some investigating and testing, I narrowed it down to 1 loop and isolated it from the system, and no more air...next step will be to cut the ends and pressurize with air and try and find the leak location..I put a pressure gauge on the lop and it loses pressure over 10 to 15 minutes...I think its a screw through the pex and as the screw rusted it let in air and maybe some water out, but most of the pex is buried in the ceiling behind lots of insulation and a water proof insulated plastic he put up under the fiberglass insulation..im glad he did the pex and its not my doing..but I get stuck fixing it..
 
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