Slab shower p-trap leak

[digitallogik]

Hello everyone,

I discovered an interesting situation in my basement this weekend. Apparently my tub has been leaking over the course of the last few months and I discovered a nice mold growth along with the leak. It looks like the p-trap for the tub was never backfilled with concrete after they did the plumbing as you can see from the pictures. I'm wondering if this is a typical thing or if this could have contributed to the waste pipes cracking/leaking? I was thinking the moving motion of entering/exiting the tub may have caused the PVC to crack against the cement? I suppose I won't know until I cut it out of there.

Does anyone have any tips on determining where this leak could be coming from? I was thinking food coloring in the drain to see if it comes up from the p-trap or not. I can't see any visible cracks and after shopvacing it out and running the tub it very slowly fills back up(10 minutes?) to the level you see in the picture.

We do not use this tub (havn't for about a year now) so I was also wondering if the water from the sink/floor drain/laundry could also be flowing back into this p-trap.

Also I'm not sure what the black capped pipe is supposed to be for? It looks like it might be a vent pipe, but it doesn't lead all the way to the attic?

Thanks in advance for any advice you might have. This is the first time I've done any major plumbing repair other than installing faucets/toilets and I'm just hoping someone can give me some good pointers so I don't screw anything up.

 

[Caduceus]

Typically the area around the p-trap is not filled with concrete. The black cap that you see is an air admittance valve (auto-vent). It should not be behind drywall. Adding a few fittings to bring it out for accessability before you repair the drywall would be beneficial. It would also be in your best interest to make an access panel for the waste/overflow and valve for future servicing.

 

[digitallogik]

Plumb-Crazy,

Thanks for taking the time to respond. I thought that (newly learned term, thanks to you)air admittance valve looked fishy. Where is the best place to bring it out to? Should it be brought out to an external wall or up into the attic?

Any advice for the repair of the leak?

 

[Caduceus]

By clearing out as much dirt as you can and exposing the piping would be the first place to start when looking for the leak. Some food coloring isn't a bad idea as long as it doesn't stain the tub interior. Is there a possibility of the leak coming from another area near the tub? The picture shows a 2" pipe and cleanout tee. Also, the tub should be secured to the framed wall and should never move or shift when entering it. If it does move, that problem needs to be addressed too.
You can relocate the AAV to anywhere in the house that you choose as long as you can get to it. Even just putting an access panel where it already exists would be an improvement. We certainly don't expect you to start hacking your house up. The important thing is that you can get to it to change it or use the adapter that it screws into as a cleanout.

 

[digitallogik]

Plumb-Crazy,

Thanks so much for the advice. I'll do some clearing out tonight and some additional investigation into the leak before I start taking out PVC. The tub doesn't shift at all, I was just wanting to make sure I don't repeat the mistakes that caused this and thought that could be a culprit. I'll make sure to put an access panel in. This corner has been hidden by a cabinet to hide it anyway. That's what caused the problem to be masked for too long.

 

[digitallogik]

Tried to clear as much as possible out of the hole. It looks like its not Mud showing there at all. That's some type of wet quick concrete that they used to re-fill the hole so I can't really get access to anything. I might try chiseling some of the concrete away to get under the p-trap.

One thing (red flag?) that I tested was taking some food coloring with a cup of water and putting it down the drain. I did not see any coloring show up in the hole, the water is super clear. I was expecting to see some coloring leak out from the bottom of the p-trap. I tried running the tub/sink/toilet and other fixtures in the house and it didn't seem to affect the level or rate at which the water is filling in at. It always seems to stop at around the same level. I can see its not dripping from the supply lines going to the tub.

I've been wanting to replace this tub with a shower for a while now, so I think I'm going to remove the tub and get a better look at what is going on underneath. I'd appreciate any ideas anyone would have in trying to track down the source of this leak. I'm hoping that pulling the tub will help.

 

[havasu]

Removing the tub will obviously allow easier access to your plumbing. You can rent an electric jack hammer which will make removal of the concrete around the pipes an easy task.

 

[Caduceus]

Looking at it from another perspective, let me ask this: If there was no use of the tub in the past year and no visible leaking from above drains or water supplies could this water possibly be pushing up from below the concrete? Soil saturated with ground water? It's not uncommon that this happens even if the whole basement does not sit below outside grade.
If this is the case you will have to look into a few options to resolve the moisture issue so that your basement doesn't become lined with mold and mildew.
Scoop out the area around the trap and use no water for about an hour. Come back and see if the hole is full again. Just a shot, but let's see if it hits something.

 

[digitallogik]

When I shop vac all the water up, it does re-fill even when not using any fixtures in the house, but I haven't tried continuously removing the water to see if it will eventually go down, I'll give that a shot tonight with the water main off for good measure. I'm also going to take a look at the water gauge to make sure its not coming from the sink or toilet supply. I will most likely save the tub removal for this weekend.

We did water issues coming in from a crack on the opposite side of the house during very heavy rain that I solved with a new downspout last year. As far as I know, there wasn't any moisture around this area during those rains. As part of that work I also re-graded all around the house. It had been pretty dry out for about a week before my discovery too so hopefully that's not the issue.

 

[digitallogik]

After my diy struggle I called in a pro he was pretty sure its ground water and recommended a sump pump to fix the issue. Im going to go ahead with that and hopefully my worries are over. Ill follow up when the water is gone. Thanks for your help. It looks like you were right plumb-crazy.

 

[digitallogik]

Big delay on the update, but I figured I owe one. I did some more exploring. The issue was actually a leak in one of the pvc joints in the wall of the floor above. I had to remove the Tub and quite a bit of drywall to find it. There was a small leak causing gradual water build up every time the kitchen sink/dishwasher were used. I think the ground was saturated because of how long this has been happening. It was hidden enough that I wasn't able to spot it until I noticed the water was a bit soapy. I'm very glad I didn't go with the Sump-pump option. I'm now enjoying a new shower/dry basement.

 

[phishfood]

Good to hear, thanks for following up with us.