Mysterious Plumbing Leak

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1,601
Location
MD
Two times now I've had a leak in the master bath, falling down into the ceiling in the basement. I had a plumber come out and he couldn't find much. His theory was that the shower had soaked the area outside the tub and it had trickled down. Now the leak is back and it can't be what the plumber theorized, because I was able to stop the leak by tuning off the supply at the hot water heater. It seems to be clearly coming from the hot water line. This is what I thought it might have been in the first place, but I trusted the plumber. Since I have turned the water back on at the hot water heater there have been no leaks. I'm stumped. It can't be a pin-hoe leak in a pipe can it? That wouldn't go away. Might it be a valve?
 
Messages
386
Location
Finland
Maybe it's caused by thermal expansion, something starts to leak when line gets hot as you use some hot water. Good time to do some re-piping before larger leak occurs...
 
Messages
1,676
Location
Waldorf, Maryland
Do you have a humidifier on your furnance? If so, were is your furnance? The saddle valves used to furnish water to a humidifier can leak, even when turned off. Usually if you tighten the hex shaped top of the valve, it will stop leaking
 
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Messages
539
Location
Illinois
Had a tub that only leaked when someone stood in the tub to take a shower. It didn't leak if you just ran the water with the no one in the tub. It was the drain connection.
 

JTK

Messages
13,432
Location
Buffalo, NY
We had a similar situation in our last home. One day a wet spot occurred in the kitchen ceiling, somewhat near where the 2nd floor full bathroom was. I figured one of the kids overflowed the toilet, or got water on the floor from the shower, etc. Next day water started dripping out of a kitchen light fixture base! Called a neighbor plumber for assistance on this one. We popped a hole in the skim-coated lath board ceiling only to be met with a torrent of water. Quickly threw the trash can under to catch the water. Had no choice at that point but cut some exploratory holes in the ceiling. We found a pin hole leak in a copper water line, where the pipe corroded through. All the piping up in there looked sketchy, including the old galvanized waste lines. Long story short, all new plumping, from the upstairs bathroom fixtures, right down to the basement. $1200
 

ET16

Thread starter
Messages
1,601
Location
MD
Originally Posted By: another Todd
Can you get ahold of a camera snake that you could stick up in there and look for the leak while it is active?
The difficult part is I don't know how to get it to leak. It's related to the hot water line, but I don't know the conditions that set it off.
 

ET16

Thread starter
Messages
1,601
Location
MD
Originally Posted By: wymi516
Had a tub that only leaked when someone stood in the tub to take a shower. It didn't leak if you just ran the water with the no one in the tub. It was the drain connection.
The plumber thought it was probably the drain at first, but it wasn't.
 

JTK

Messages
13,432
Location
Buffalo, NY
That's how it was on our previous home, a cape-cod style built in the early 1950's. No access. Had to pull drywall. I'd suggest that's what you do where you see water. Problem is, water can travel long ways.
 
Messages
15,859
Location
NE,Ohio
how is the water pipe ran? I had a spot in the bathroom that went plastic pipe >>different size plastic pipe >> copper pipe within 3ft of shower.. one of the joints in the middle of the floor cracked from flex/water hammer it would only leak when the toilet was filling. That one took awhile to find. Punched some holes in the floor by wall by picking up the tiles then sawing into the boards with a vibrating cutter. fished a camera/scope through the floor between the boards.. finally found it.. moved over 5ft made a 2x1' hole and fixed the pipes, then reinforced the boards,layed them back down and fixed tiles. total MASSIVE PITA
 
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ET16

Thread starter
Messages
1,601
Location
MD
Originally Posted By: sciphi
Shower blend valve failing or associated piping leaking? That's where I'd guess.
That's interesting. My wife said that the pressure was different in the shower. I think the leak is lower than the valve in the wall, though. My guess is that it is leaking around the hot faucet for the tub. I see that they are connected somehow, but can't get a good look through the access panel.
 
Messages
2,081
Location
California
If this is a two- or three-handle tub/shower valve, it's possible that the stem on the hot side isn't tightened all the way into the valve body, or that the gasket between the valve stem and body is leaking. You can check this by turning off the water to the house, and unscrewing the hot stem. After checking the gasket, make sure the stem is in the "open" position when you screw it back in.
 
Messages
2,806
Location
Michigan
I helped a buddy of mine diag a similar issue, One this we realized that the water will run down and then parallel following a floor joist. one of the hot water pipe joint is loooooose and leaking. do you have plex or copper throughout?
 
Originally Posted By: ET16
Originally Posted By: another Todd
Can you get ahold of a camera snake that you could stick up in there and look for the leak while it is active?
The difficult part is I don't know how to get it to leak. It's related to the hot water line, but I don't know the conditions that set it off.
It has probably been leaking for a while, you may be able to see signs of past leakage, like calcium streaks, green build up on copper etc.
 
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