Finding leak in PVC conduit
#1
11-01-21, 04:39 PM
Join Date: Nov 2021
Posts: 5
Upvotes: 0
Received 0 Upvotes
on
0 Posts
Finding leak in PVC conduit
I have kind of a strange situation and I'm hoping some of you have some ideas. I have an outdoor wood boiler which runs heated water through pex tubing in to my basement. The pex tubing runs through a 4" schedule 40 PVC conduit buried 2-3' underground. I noticed this spring that there was water in the conduit (not leaking from the pex tubing, but seeping in from the ground). I had the pipe partially replaced this summer and maddeningly enough I still have water in the conduit. I have an idea of the general vicinity where the leak likely lives as part of the pipe passes through a pretty boggy area in the yard. I have now uncovered all of the joints in the boggy area and am prepared to cut the pipe and apply a boot. However, it is not obvious to me where the bad joint is (none of them appear abnormal grossly). I've capped 1 end and mostly capped the other end and tried to pressurize the pipe with a shop vac +/- air compressor but I'm not sure that I'm getting enough pressure to actually see bubbles (I filled up the holes with water to try to see any bubbles better). At 1 point tonight I thought sure I saw bubbles near one of the joints but it was not a repeatable phenomenon. I just want to make sure I'm addressing the problem and not potentially cutting through good pipe and ignoring the actual problem in the next joint. Any ideas? I understand this is a weird setup and my explanation might be confusing - let me know what questions you have. Thanks so much for any help or ideas you have!
#2
11-01-21, 04:53 PM
Group Moderator
One of your issues is that PVC conduit was used. PVC conduit is not really designed to keep water out. That is why wires installed in PVC conduit that is buried are required to be water-resistant.
Is the water hurting anything? What about just coating all the joints with a sealant such as Flex-seal?
Is the water hurting anything? What about just coating all the joints with a sealant such as Flex-seal?
#3
11-01-21, 05:07 PM
Join Date: Nov 2021
Posts: 5
Upvotes: 0
Received 0 Upvotes
on
0 Posts
I had to use PVC as it goes under a driveway and needed to be strong enough to withstand the weight of cars - the other option is black corrugated but the guy who installed it said that wouldn't be strong enough. All of the joints were primed and glued. As for whether it's hurting anything - I mean technically no, but the water is stealing my heat! - it's a terrible insulator and is forcing my wood consumption to go up unnecessarily. Is the flex-seal a better option than a boot? Or i guess it's probably better because i wouldn't be cutting any pipes?
#4
11-01-21, 06:43 PM
Group Moderator
I was thinking that plumbing PVC would have been a better choice than electrical conduit as it is designed to keep water from leaking in or out. But really that is moot now. 
Just wondering, is it really an electrical conduit? I ask because you can only get 4" conduit from an electrical supplier.
Yes, I think just sealing them on the outside is a good option as you are trying to keep water out of the pipe. Goobing the joints with something like Flex-seal and/or Flex-tape might be good options. Somebody else may have a good product suggestion.
Just wondering, is it really an electrical conduit? I ask because you can only get 4" conduit from an electrical supplier. Yes, I think just sealing them on the outside is a good option as you are trying to keep water out of the pipe. Goobing the joints with something like Flex-seal and/or Flex-tape might be good options. Somebody else may have a good product suggestion.
#5
11-01-21, 10:42 PM
Member
The pex tubing runs through a 4" schedule 40 PVC conduit
If it's the gray then per prior notes your going to have issues. It was never designed to be water tight let alone pressure rated (not that yours is) so the joints were never intended to be "perfect".
The only thing I can think of is some type of Fernco boot but as you have found it's a tiny, very tiny, leak and you would pretty much have to address every joint if you cant find it.
Another option, slide a new pipe inside the existing PVC! Probably not a fun option.
#6
11-02-21, 04:53 AM
Join Date: Nov 2021
Posts: 5
Upvotes: 0
Received 0 Upvotes
on
0 Posts
Oh interesting - no, the original pipe was the grey with flared ends - when we replaced it this summer we used the white with the collars. I didn't realize the colors mattered - but it sounds like we replaced electrical conduit with plumbing pipe? So I should have a chance to make it water tight? It's maddening to me (a non-professional) because all I'm asking this pipe to do is sit in the ground and keep the outside out. There is absolutely no pressure in the pipe. The new inner pipe option i think isn't possible as the pex tubing has several layers of insulation around them so there's not a lot of clearance (and there's also several angles). Thank you all for your advice!
#7
11-02-21, 10:09 AM
Are the ends of the PVC pipe sealed? Warm, humid air could be coming in from the house side and condensing, causing water in the pipes.
I'm surprised cemented PVC pipe is allowing water in. Even with a dirty or poorly cemented fitting, they usually are quite secure, even with pressure systems (which yours isn't).
I wonder if you'd be better off setting up some kind of drain instead. At a low point in the pipe, drill and let drain into a small gravel drywell underneath. Not sure if it would be better to set it up somehow so you can drain it once or twice a year, or just leave it open. I can't imagine the water coming in is that significant - especially since it's coming in just through wet soil (and not like you're going under a stream).
I'm surprised cemented PVC pipe is allowing water in. Even with a dirty or poorly cemented fitting, they usually are quite secure, even with pressure systems (which yours isn't).
I wonder if you'd be better off setting up some kind of drain instead. At a low point in the pipe, drill and let drain into a small gravel drywell underneath. Not sure if it would be better to set it up somehow so you can drain it once or twice a year, or just leave it open. I can't imagine the water coming in is that significant - especially since it's coming in just through wet soil (and not like you're going under a stream).
2john02458
voted this post useful.
#8
11-02-21, 11:26 AM
Group Moderator
PVC makes great conduit and can be waterproof if the joints are properly glued. I have numerous similar conduits on my property. Condensation is a problem if the ends aren't sealed. Even in the ends of your conduit are in areas that don't get wet humid air gets into the pipe and then when it hits the cool underground pipe the moisture condenses into liquid. Since there isn't much airflow very little evaporates away so over time the pipe can gradually fill with water. That is a big reason insulated PEX is used for connecting to a heater like you are doing.
Depending on your water table you could construct a French drain underneath a low section of the pipe. Then drill a drain hole for the water to get out. The big drawback is a period of heavy rain or spring thaw when the ground is saturated you could have water rise up into the pipe.
You could snake another piece of PEX into the conduit and attach to a pump or wet/dry shop vac and occasionally suck out the water.
Depending on your water table you could construct a French drain underneath a low section of the pipe. Then drill a drain hole for the water to get out. The big drawback is a period of heavy rain or spring thaw when the ground is saturated you could have water rise up into the pipe.
You could snake another piece of PEX into the conduit and attach to a pump or wet/dry shop vac and occasionally suck out the water.
2john02458
voted this post useful.
#9
11-02-21, 05:38 PM
Join Date: Nov 2021
Posts: 5
Upvotes: 0
Received 0 Upvotes
on
0 Posts
oh wow that's a really good reminder. The pipe is usually sealed with spray foam on both ends but since I tore it out this summer the ends have been open. I talked with a local plumber today and got a cap for one end and an air valve with a PSI gauge for the other end today - my plan tomorrow is to see if the pipe can hold 5 PSI for any period of time. If it holds, then it's probably the condensation issue. If it doesn't, then hopefully the bubbles will lead us to the problem. Sound sensical? Thank you all for your help and advice!
#10
11-02-21, 05:53 PM
Join Date: Nov 2021
Posts: 5
Upvotes: 0
Received 0 Upvotes
on
0 Posts
That brings up another question - is the spray foam appropriate for sealing the ends? I'm quite convinced the water I was getting last winter/spring was secondary to ground water as the entire pipe should've had warm air in it, the ends were sealed with spray foam, and the amount of water seemed to vary with the amount of rain/snow we had. But the current water situation may be caused by the unsealed pipe. Once I get things under control and dried out, is spray foam an adequate choice to seal or do I need to do something else?
