So there is usually a rubber gasket between the tank and the stool that can leak. You'd find moisture under the tank on the floor if that were the case. Generally there's two gasketed bolts holding the tank to the stool and they can also leak. Tightening those a bit can fix either or both leaks of this type. Does anyone in your house lean back against the tank whilst copping a squat? That will cause a leak if things are loose enough...a leak that stops as soon as lazy leaning Mofo gets up.penningtron wrote: Fri Mar 24, 2023 7:27 am Has anyone ever dealt with a toilet basin that refills every couple of hours for no reason? I'm guessing there's a slow drip near the seal but I haven't been able to detect it when I open it up. It seems to happen more when the temperature changes although it's been more frequent in recent weeks. Could this be as simple as replacing a rubber ring around the seal or do I need a whole new assembly? (bonus points if you know the actual names of these parts)
The flush lever opens a valve (the flapper) that dumps the tank. Could be that flapper inside the tank leaks a little bit. The tell there is you might see a little bit of dribbling from the top of the stool bowl down into the pool of water below. The level of the pool is basically set by the tank level and gravity. You can adjust the tank level and the inlet water shutoff point by adjusting the float in the tank. That won't fix a wonky dump valve though, you'd have to replace it. Got rusty water? Buildup on the tank bottom can make the flapper not seal well.
Fresh water generally enters the tank from the bottom and it goes into a standpipe in the tank that the float attaches to. The standpipe often has a gasket where it meets the bottom of the tank. That can leak slowly if the connection isn't tight. Again, this would be a leak external that you'd more than likely see on the floor under the stool.
Worst case, the big wax ring that seals the bottom of the stool from the floor is bad and is leaking. That may be leaking under whatever the visible floor surface is and you find the leak the hard way when the floor under the stool rots out. I'm not sold that this is your problem UNLESS you notice that the level in the bowl drops slowly over time. That can drop if the wax ring leaks, but the tank doesn't know that water has left the bowl. Since the tank keeps refilling, your leak is more than likely the internal flapper valve or the tank-to-stool connection.