I have a rental that is currently unoccupied, tenant moved out in April, and I have been doing stuff to get it ready for rent. Because of that I have been spending time at the unit - painting, replacing the sink cabinet's floor, changing out some stop valves, replaced the central air system, running some new CAT6 cables etc etc etc...

In early June, I noticed the toilet, when flushed, would have some water seep out of the base where a grout line is.

OK so the wax seal is broken. I didn't notice it before, been using that toilet the entire month of May, no leak. I also had hired pros to replace the kitchen counter top, reglazed the bath tub etc...and they used the toilet, no leak either. Just one day in June I saw the leak after flushing.

I got curious, so I used a razor blade to break the caulk around the base of the toilet, thinking I need to remove the bowl to redo the wax ring. The caulk was done all the way except not completely sealed where the grout joints were lowered so that's why it came out of the joints.

But a day later, I flushed it again, no leak. I tested it three times in a row, holding the lever down to get max volume into the bowl, no leak either. Hmmm, I threw some TP into the bowl, flushed again, no leak.

So I went ahead and proceed with other projects in the unit, and keeping an eye on it in the mean time, each time after use, no leak, except one day, it leaked again, flushed again, leaked more. After that, no more leak since, no matter how many times I flushed in succession, with or without TP.

Why is this intermittent behavior? Is it a temperature thing that slightly warmer or cooler could make a difference on the wax seal? Should I pull the toilet and replace the wax ring? It leaked twice in the entire month of June. I would say it the caulk was done all the way around with a good seal I may not have even noticed it.

Intermitent leaks can occur if the toilet flange is not securely anchored to the subfloor. Temperature changes cause the stack to expand and contract and this movement gets transferred to the toilet flange.
Had a case where the customer noticed a pattern - water leaked out from the base of the toilet after flushing after the wife took a shower. She took long showers. Stack was ABS which expands a lot when warmed.

Rubber gasket helps to accomodate small movements of the flange, at least for a few years till the rubber hardens.



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Any chance there's a sewer pipe restriction and there was a lot of water used, prior to the leaky flush, that the flush was too much water, too fast, for an already filled sewer pipe?

steve, I doubt it. It doesn't seem to happen based on how many flushes in succession. In other words, no one has been at the apartment and I go there and first time use it could leak, but if I got curious and flush 8 times after that some straight flushes some I threw in some TP to change it up it may not leak. Nothing ever back up in the tub right next to it either.

Next time I go there I will fill the tub up and pull the stopper so the pipe will be full of tub water, and once the tub is empty I do a flush and see if it leaks.

George I don't know how it's plumbed by it's a concrete slab and 1960s plumbing all cast iron. I don't think it's stack vented but could be.



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Use a Fernco FTS-? seal