When I turn on the cold water in the kitchen sink, the first 30 seconds or so the water is hot. I believe there is a cross connection somewhere. Our home is only 2 years old. No plumbing has been changed since the initial construction. How do I trace the hot and cold water pipes in the basement to determine where the cross connection might be? Cheri

Hmmm... wondering if your cold water pipe runs up tight to the boiler in your house or through a warm spot.. Is this problem present during the summer..

Answer those questions and I will see if I can help further! Thanks.

I don't know if this is where I am to answer the questions asked by massplumber or not, but here goes: THe cold water pipe does not run next to a boiler but there is a warm spot under the kitchen sink. The duct work for for heat/cool vent air is under the sink and exits out the toe kick in the front of the sink base cabinet. There is, however, a lot of insulation around the vent. I know in the summer the water seems warm, also, but I always attributed that to the water in the tower that services our subdivision heating up from the sun and outside air temp.

Not sure yet, but at this time if you cannot say that the cold water is hot in the summer but it is hot now AND there is a heat/cool vent near it (never mind under the floor)... I am leaning toward the obvious... but let's see:

Every time you turn on the kitchen faucet cold water... it comes out hot for 30 seconds.. Can't be every time... right? I will try to check back in 10 minutes...

OK, I tested it. I turned the water on until it ran cold for 30 seconds (30 seconds of hot, then it turned to cold and let that run additional 30 seconds) I then turned it off and waited 5 minutes and ran it again. Initially the water was somewhat warm, not as hot as usual, and it took less than 30 seconds to turn to cold. Hope this helps.

OK, I tested it. I turned the water on until it ran cold for 30 seconds (30 seconds of hot, then it turned to cold and let that run addtional 30 seconds) I then turned it off and waited 5 minutes and ran it again. Initially the water was somewhat warm, not as hot as usual, and it took less than 30 seconds to turn to cold. Hope this helps.
Hey! Got a idea people! Go down to the cold water supply pipe in your water heater after it's been setting without a hot water draw. Now feel the cold water supply pipe back from the heater. Is the pipe warm to the touch? How far back before it begins to turn cold?
This is called convection. What I think's happening is that when you make a cold water draw it runs the cold water out of the pipe until it begins to suction the hot water in the cold water supply back into your kitchen branch until the hot water ran out and the cold took over. Installing heat trap nipples on the heater may help this situation . Good luck, Tom

I will heck this method and see what I find. Thank you.

That's it... only thing that makes sense. I have seen it before.. but I was right there and could do the trace myself. Knew we could count on you Speedball1. Thanks.