I added a shower to my place and now I got hot water coming out of my cold taps for the first 15 seconds or so. All I changed from before was to add 2 tees into the line, one from the hot and one from the cold water lines. What's happening? Thanks.

Do you have a hot water recirc pump on your system? If you do, make sure you didn't tie into the recirc line instead of the hot water feed line. Also, how close to the water heater are the tees you installed?

I have no pump and the tees are about a foot and a half from the hot water tank.

This might explain your problem. When the water in the water heater is not used for a while the heated water in the tank will expand and go backwards into the cold line, also the law of phisics applies here that hot rises and cold falls, therefore again you have hot water rising into the hot water line. Since your tee's are so close to the water heater some of the hot is backed up in the cold line that furnishes your new tee and until the hot is flushed out you will get the small amount of hot water out of the cold line.

If you have some one to help you check this you check the heat in the cold water inlet at the heater and see if it is real warm and when someone turns on the cold in the shower it gets cool.

If this is the case, nothing to worry about really. If you just can't stand it. You can install a either a heat trap, or a heat trap nipple off the top of the cold inlet side of water heater. If you do go the heat trap route, make sure that the trap is between the water heater and any other colds that come off the cold water heater supply

I installed a check valve at the hot water heater and that fixed the problem totally. Thx to everyone for their info.

I installed a check valve at thhe hot water heater and that fixed the problem totally. Thx to everyone for their info.

Congratulations... Milo

I installed a check valve at the hot water heater and that fixed the problem totally. Thx to everyone for their info.

Putting a check valve in the incoming line to a water heater is not a good idea. The reason being that in a case where the gas to the burner fails to cut off you do not have a one hundered percent safety that steam will not build up in your heater and create a bomb.

And yes I know that you have a pop-off valve for such emergencies, and you have a cut off build into the thermostat to protect against this sort of problem. But none of them are one hundred percent positive protection.

I can see LetmetellU s point about the check on the cold water supply but if there's already a backflow preventer install the system's closed already. I didn't think of that in my reply. Thinking it over I think you're absolutely correct Lee.
A check valve and expansion tank it is. Cheers, Tom

I think you will be just fine with the check valve, but you will need to add an exansion tank on the water heater side of check valve. Many areas require a check valve on home incoming water anyway, so installing one on the cold supply of water heater makes no difference.(except to cure your problem of hot water in cold line) The reason for the expansion tank is so that when the water in the water heater heats up and expands, it won't blow off your temp/ pressure relief valve. I personally would have like to see you use the heat trap nipples, but a check valve will work just fine to.. Just make sure to get that expansion tank install asap. With a check valve installed right before water heater, it wouldn't hurt to manually pop off your pressure relief vavle now and again just to make sure it is not stuck. 'The only problem with this is,, once you pop them off manually, they tend to drip, so I would have a spare one on hand just in case you can't get it to shut down completely.

Tom, just wondering how an expansion tank will take the place of a check valve. I don't think an expansion tank will keep the heat from radiating up the cold side. But I have been wrong before, and I promise I will be wrong again(most likely many times.. )

Tom, just wondering how an expansion tank will take the place of a check valve. I don't think an expansion tank will keep the heat from radiating up the cold side. But I have been wrong before, and I promise I will be wrong again(most likely many times.. ) Well Lee, you're not wrong this time. You will always have convection, especially with metal pipes. But we 're not talking about convection are we? If you havea sprinkler system and a backflow preventer install you have a check valve installed.
While nether a check valve or a expansion tank will stop heat from convecting up a metal pipe convection only carries a few feet.
What we have here is pressure building upin the tank and forcing the cold water back up the supply. That's where the expansion tank comes in. Instead of traveling up the cold water line it expands into the tank. I can see LetmetellU s point about the check on the cold water supply but if there's already a backflow preventer install the system's closed already. I didn't think of that in my reply. Thinking it over I think you're absolutely correct . Let him try both a check valve and a expansion tank. I'll go back and do some changing. Cheers, Tom

Thac for the info. I will add the tank to allow for the expantion. Thanks again the info is appreciated. Jim
I think you will be just fine with the check valve, but you will need to add an exansion tank on the water heater side of check valve. Many areas require a check valve on home incoming water anyways, so installing one on the cold supply of water heater makes no difference.(except to cure your problem of hot water in cold line) The reason for the expansion tank is so that when the water in the water heater heats up and expands, it wont blow off your temp/ pressure relief valve. I personally would have like to see you use the heat trap nipples, but a check valve will work just fine to.. Just make sure to get that expansion tank install asap. With a check valve installed right before water heater, it wouldnt hurt to manually pop off your pressure relief vavle now and again just to make sure it is not stuck. 'The only problem with this is,,, once you pop them off manually, they tend to drip, so i would have a spare one on hand just in case you can't get it to shut down completely.

Tom, just wondering how an expansion tank will take the place of a check valve. I dont think an expansion tank will keep the heat from radiating up the cold side. But i have been wrong before, and i promise i will be wrong again(most likely many times..)