Toilet filling with hot water

I recently had water damage in my apartment-style condo that affected the bathroom floor. The contractors disconnected the toilet and tore out the sink before replacing the flooring and hooking everything back up.

Upon checking the toilet, I noticed that it was now filling with hot water, which it never did before. I've complained to the company that did the work, but they say that the work they did couldn't have caused it and it might be related to the original leak repairs - that maybe they crossed up the pipes or something. However, every other hot and cold faucet in the unit (including another toilet) is working normally.

My suspicion is certainly that the contractors somehow hooked the toilet up to the wrong water pipe when the reinstalled it, but how likely is that? ANd can people think of any other possible causes for this?

For example, I've read about faulty shower mixing valves being causes of this kind of thing.

The immediate concern is hot water in the toilet can break it. They are not designed for hot water. I don't know who did it, but someone has screwed up your plumbing. Without knowing how your pipes are run, I can't tell specifics on how to trouble shoot this, but try to trace the cold water line that should feed the toilet and see if you can find where the wrong connection was made. If you can't find it, you've got to get a plumber in to find the problem. After the problem is found you should be able to figure out who was responsible and make them pay for the repair. In the mean time, I'd play safe and use a bucket to pour cold water into the toilet tank after flushing. I know it's a PITA, but not as bad a having to replace the toilet.

I wouldn't think that removing a lav and a toilet would cause a reversal like that.
Normally the water supply for the toilet would have stayed in place, and it would just be a matter of reconnecting it.

I've seen some lavs reversed at the wall in condos, and the water supplies either flipped, or the cartridge spun in the faucet to turn it back.

In plumbing, the supplies are by tradition installed with the hot on the left and cold on the right. Faucets are made to operate that way. But, when the plumbing is tight, AND if the fixture can support it, (like in a back-to-back situation), it is just easier to have it right on one wall, and on the opposite side of the wall use the same stuff (but now 'reveresed), but reverse the guts of the faucet or shower to obtain proper operation. If the person who installed the pipe didn't realize that the pipes may have been reversed on your side, he may have connected to what he thought was the cold line, but in reality, it was the hot one. It would have looked perfect before water was turned back on and things hooked back up.

Turn the hot water off at the cold water inlet to the water heater and see if your toilet still has flow. If it was piped with hot water you should have no flow with the cold water to the water heater turned off.

Check that and get back with me.

The problem is that I don't really have access to the building water heater. I can request access, but that will take a while.

If it's possible that a faulty valve in the shower is causing it (bearing in mind that the cold and hot for both the shower and sink in that bathroom work fine), any ideas on how I can test to see if that's the cause rather than the piping?

I agree that it's really hard to understand how the piping could be the issue if all the contractors did was remove and then replace the toilet, but one other thing I forgot to mention was that originally the toilet wasn't running at all after they finished and we had to call them in to adjust the supply valve to get it going. It makes me a little suspicious that they left things with the water off - almost like they were trying to hide a screw-up.

Turn on all the cold water faucets in that bath and flush the toilet......see if its still hot water. Check the temp with your hand of the cold at the lavatory and the shower and see if its still cold.

If there is a janitor’s closet, close to your apartment, with a mop sink or something similar, a cross-flow can occur if there is a hose with a sprayer on the end of the hose and the handles on the mop sink are left in the on position. Also if there is a soap dispenser connected to the mop sink and both the hot and the cold handles are left in the on position the same thing can happen. I was at a McDonalds recently that had this same problem. The employees said they liked it because the toilet was warm when they sit down.

If they did not do any repiping, the toilet would be connected to the sink's and tub's cold water pipe. Therefore, if the sink and tub have cold water the toilet should also. Therefore, something was done hat we are not be told about.