Leaky Toilet?

Sporadic leakage visible on cross beams under the floor. Soaks beams and insulation. Able to replicate once by running all water in the house; however, unable to isolate leakage to a specific source. Suspect that the leak is coming from a hall toilet approximately 10 feet away from the leak. Water must travel under hardwood floor and then settle down into the cross beam(s) located under the hallway, just outside the half bathroom area. Toilet was recently replaced when the hardwood floors were refinished and does not rock or wobble. No visible water damage above floor, or on plywood between the floor and cross beams.

Any ideas how to definitively know it’s the toilet and not the sink? Why would something leak just occasionally? The house is vacant and up for sale so we need to know that the problem is identified and corrected properly. We believe it leaks when someone uses that bathroom, but don’t know if it is the sink, toilet or something else. My husband just wants to take up the toilet and replace the seal hoping that will solve the problem. I’m worried since the leak is so sporadic, once every week or two, that we’ll not really know for sure if the problem is solved. Any help would be appreciated.

If it's not a constant leak it is most likely a drain issue. Run each fixture seperatly (at different times) and see what one it is. If all three it is most likely a branch drain(drain where all three convey thru). I bet the culprit is your water closet, most likely not properly sealed with wax ring.

Thanks for your response. There is only a sink and toilet in this bathroom and I've tried running just the hot water, then the cold, and then both together and nothing leaked. I later flushed the toilet ten times and nothing. We go there a couple times a week and flush the toilet, but nothing leaks.

The house is built on a basement so the drain pipes are visible in the garage, so we're pretty sure the water is leaking higher up. Areas around where the drain pipes come out are dry.

It hasn't leaked in a week and is all dry now. If we remove the toilet would we be able to tell if the seal is bad?

Look at the supplies under the sink and the water closet. You may find a slow drip there? You may not be able to tell by pulling the water closet, but if you have time and are able to do so, try it. If you pull toilet observe the closet collar is it well below the finish floor. Maybe you just need a thicker wax ring. Hope I can help you in one way or another.KEEP POSTING.

We took up the toilet and replaced the wax ring. There was no sign of visible damage on the wood surrounding the flange.

All the supply lines are in the walls for both the toilet and the sink. I really would like to know if any are leaking, but if we cut out wallboard, we will have to take down wallpaper too. If it continues to leak, I guess that's our next step.

I guess we just have to wait now and see if anything leaks again. It only leaked about once a week or less, so I guess there's no way to know for sure that we fixed it.