Hi,

I have a major issue of hot water going into my toilet tank. I have replaced the fill valve and the ball, and I have no mixing valve on my toilet, only a central mixing valve for the entire house ( as far as I can tell). When shutting down the mixing valve, the hot water doesn't mix with the cold anymore therefore, I know that central mixing valve works. But I don't understand why hot water is coming to the toilet bowl still.
I have 2 other toilets, only 1 has this problem. Any ideas what might be going on ? I'm getting very worried that this is a major issue, major like, I need to rip out some walls issue.

How long has this toilet been getting hot water, was it once cold? Do you have a hot water recirculating system? Is this toilet very close to the hot water heater?

Answer Bobs questions and I have a few of my own.
Any plumbing work done or new faucets or fixtures replaced lately? Any one handle faucets acting up? Answer us and we'll answer you. Regards, tom

The house is 6 years old. The hot water tank is hooked to a ventilation system, that's what heats up the house. The mixing valve ( the only one I know of) to regulate some hot water going into cold water to avoid condensation, is centralized and attached to the hot water tank.

Toilet isn't close to heating system. Getting hot water for last 2 weeks only. Yes the water was cold before. No plumbing, replacement of faucets or anything at all has been done before.
And what is a hot water recirculating system??

A hot water recirculation system is a pump on the hot water lines that moves hot water through the house at all times so you get instant hot water when you open a tap.

The hot water tank is hooked to a ventilation system, that's what heats up the house. Tell us more about this hookup. You have a hot water boiler heating your home and a hot water heater tied into that?

The mixing valve ( the only one I know of) to regulate some hot water going into cold water to avoid condensation, is centralized and attached to the hot water tank Let me explain. Every one handled faucet is a mixing valve.
Something's changed in your system in the last few weeks to cause this problem. Can you think of anything?
Cheers, Tom

This heating system is particular and rare. It's called a hi-velocity forced air furnace I believe. My hot water tank serves to both, provide hot water to the house and heat up my house. The hot water tank is connected to a ventilation system which pushes air into the house.

There is nothing that changed in the last week or so in my house. Nothing at all. Thinking about it some more, I realize that there is probably a leak that occurs between the tank and the toilet bowl, and that I need to change the ball again, since the water is hot in the tank and the bowl.

My theory is that : If the water is leaking into the bowl, the water level drops causing the fill valve to fill up slowly and constatnly. Since the water is mixed between the hot and cold throughout the house, the tank eventually fills up with hot water. The hot water is replaced with cold water when I flush. So in theory, if there's no leak between the tank and the bowl, there will be no constant fill up and the water should stay cold.

Does that make sense ?

My theory is that : If the water is leaking into the bowl, the water level drops causing the fill valve to fill up slowly and constatnly. Since the water is mixed between the hot and cold throughout the house, the tank eventually fills up with hot water. The hot water is replaced with cold water when I flush. So in theory, if there's no leak between the tank and the bowl, there will be no constant fill up and the water should stay cold. Does that make sense ?
Works for me! Tonight before bed time out some food coloring in the tank and let it set over night. Next morning check for color in the bowl and tell me about it. Good luck, Tom

The hot water heater is in a closet behind the toilet when I flush the tank refills with hot water and the tank gets warm to the touch

the hot water heater is in a closet behind the toilet when I flush the tank refills with hot water and the tank gets warm to the touch if it helps the toilet was installed 3 weeks ago

Someone connected the toilet to the hot water line instead of the cold.