Odd plumbing leak

[Zachary Hoyt]

I was happy a month or so ago when I ran all the new plumbing in the house and didn't have any leaks, but today a very odd leak developed that I can't understand. It is under the upstairs toilet. There is a slow seep of clear water coming out constantly between the 3" PVC coupler and the pipe below the flange. It drips about once a minute. I dried the pipe and made sure I was seeing just where the water was coming from. It's clear that I didn't get a good glue joint on that fitting and I'll need to cut it out and replace it, but the second part that I don't understand is where the water is coming from. It seems like there shouldn't be water there except when the toilet is flushed, and then only momentarily, since the pipe is vertical. Is there something wrong inside the toilet that could allow water to be getting to the joint between the flange and the coupler and the rest of the pipe, or is capillary action somehow responsible? I'll be very grateful for any advice.

[Dick Strauss]

Check the tank to toilet seal, the water supply to tank and the toilet to flange connections. Have you checked for puddles behind the toilet under the tank? It could be that the water is coming from outside the toilet and seeping around the flange from outside the pipe. You could also have a cracked toilet. You could also have a bad seal under the toilet causing a puddle to form under the toilet when when you flush. This water then seeps around the flange and it appears as if the 3" pipe connection is bad. I'm sure I'm missing other possibilities. Good luck!

[Michael Schuch]

I always sand both mating surfaces with ~80-120grit. Then apply the primer once or twice before welding with the cement. The larger the pipe/fitting the thicker the cement you should use. For a 3" pipe I would use the thick stuff. I apply a thin coat of cement on both mating surfaces before sticking them together.

I don't see any signs of the purple primer on that connection. The primer softens the PVC making a better weld.

Sorry, I can't tell where the drip is coming from.

[Zachary Hoyt]

Thank you both for the advice. There is no water getting out upstairs, or running down the side of the coupler, so wherever the water is coming from must be internal. I'll need to pull the toilet anyway when I go up Sunday or Monday, to run the flooring under it, so I'll look into it then. I didn't sand the pipe fittings but I did use clear PVC primer and applied cement to both surfaces. I must have not done it well enough, though.

[Tom M King]

I've never sanded PVC, and must have put together over a thousand joints since I got my Plumbing license in 1975. The primer cleans the pipe good enough without sanding if you use plenty of it. While the purple doesn't look good, you can see when you have used enough of it. Swab it all around a number of times. You can see when you've cleaned good enough as it dissolves the writing on the pipe.

The water might just be what's sitting on the end of the pipe. Dripping that slowly, it would take a while for it all to come out.

[Curt Harms]

Maybe put some food coloring in the bowl and flush it. See if the drips are colored. If not, food coloring in the tank and flush that. I wouldn't think food coloring would leave a permanent stain. If neither produces colored drips I guess it'd have to be the supply tube connection.

[Maurice Mcmurry]

Almost all toilets let a little water past continuously. Most hardware stores have dye tablets that can help find the problem. Sanding is not required for PVC. Primer is important and is purple so that an inspector can see at a glance if the joints were done properly. You could fix that with a Fernco rubber fitting from underneath without taking the toilet up again.

[glenn bradley]

A lot of folks today don't bother with the twist when assembling. Agreeing that it is optimal but sometimes not possible it does spread the glue prior to the cure. I always try to twist.

[Kev Williams]

In my last house I had a leak I couldn't track down, the food coloring trick found it- the tank was micro-fractured(?) and was seeping out in several places. No idea WHY it was broken?

And our mobile home, I had to replace the sub floor in the main bathroom due to an invisible leak, which turned out to be the donut gasket between the tank and bowl. It was leaking behind the tank, down the back side of the bowl and onto the floor. Must have been doing it a long time as it went un-noticed by the old owners and inspectors when we bought it. I only found out when deciding to change out the linoleum for carpet and found soggy floor under the bowl...

[Lee Schierer]

To me it doesn't appear to be a leaky joint, it looks like drips from some other location. Show us a photo of the floor right above that leak.

[Perry Hilbert Jr]

My daughter had a toilet flapper get stuck. the constant cold well water formed condensation on the outside of the pipe and dripped constantly until she realized it wasn't shut off and handled it. Perhaps Condensation?

[Bill Dufour]

painters tape or paper towels with a rubber band will show a leak.
Something is odd. Did you use a modern ring seal with the long rubber horn? Those
should prevent any water from even touching that joint. Is the vent stack wide open. Run a garden hose down it full on.
Bill D

[Bruce Wrenn]

If you separated the bowl and tank, did you put a new tank seal back between them? Make sure floor is dry, and lay a piece of newspaper behind the toilet. Any moisture will quickly show up on paper. Turn water off to toilet, and flush it, then dry out the tank. Wait a few minutes and see if there is a leak. The flapper could be leaking into seam between tank and bowl. Once the water in the bowl has stopped filling, it shouldn't send any water down the trap, unless you have a flapper leak

[Zachary Hoyt]

Thank you all for the ideas. It's a brand new toilet which I assembled as per instructions, but the wax seal didn't have a rubber sleeve. It seemed to be working fine and was not leaking for about a month, and then this started very abruptly. There is no moisture outside on the upper floor, or on the side of the coupler, so I am sure it is not coming down the outside of the pipe from higher up. I dried the whole area with a rag and then looked closely with a flashlight and felt around to determine exactly where the water is coming out, and it's right where it is visible in the picture.

[Stephen Tashiro]

It's sometimes possible to seal leaky PVC drain joints by applying primer to them.