There’s a leak that shows up on r/Plumbing constantly and it’s almost never the wax ring. It’s the tank-to-bowl gasket. The spongy seal between the toilet tank and the bowl. And here’s the annoying thing about it: people spend hours chasing the wrong leak before they find it.
Here’s what happens. You see a puddle at the base of the toilet. Instinct says wax ring. You spend a Sunday pulling the toilet, scraping old wax off the floor, installing a new ring, reseating the whole thing. Then you flush. Still leaking. Because it was never the wax ring. It was the gasket inside, where the tank bolts to the bowl.
The giveaway? The water shows up on the floor only after you flush, and it’s usually worse when the tank is full. A wax ring leak is constant. A tank gasket leak is flush-triggered. That’s how you tell them apart before you rip up the wrong part.
I make these gaskets. The thing that drives me nuts is that a tank gasket is a five dollar part. But people let the leak go for months because they keep thinking it’s the wax ring and they don’t want to deal with it. Meanwhile the water is soaking into the subfloor behind the toilet where you can’t see it.
The fix is honestly easier than a wax ring. Drain the tank. Undo the two bolts inside the tank. Lift the tank off. Old gasket out, new gasket in. Tank back on. Retighten the bolts — gently, because the same overtightening that cracks toilet bases also crushes tank gaskets and makes them leak faster.
Here’s the thing I tell every property manager and it makes them look at me like I grew a second head: replace the tank gasket every time you replace the wax ring. They’re cheap. Do them together. Because pulling the toilet to fix the ring while leaving a five-year-old gasket in there is like changing one brake pad. You’ll be back in six months.
The Reddit plumbers have a version of this advice too. Some guy with a plumber flair wrote it better than I ever could: “A $5 gasket today or a $500 floor tomorrow. Your call.”