I do not have any hot water in the house .The water heater pilot is on,there is plenty of cold water pressure.The house has copper tubing. I drained all the water out of the heater. The water heater is a RELIANCE 501,I can feel the hot water in the copper lines,but there is still no water pressure to the bathroom 10ft. away

I went to the hardware store (took my stem) and got a new seat. The guy there (who was no help) wasn't sure if the seat was the right size for my stem, even though they had carry the size stem I have. I took out the seat, no problem. The old seat was *very* corroded. So corroded, it was difficult to tell if it was the same size as the one I bought. Nonetheless, I inserted the new seat. After inserting the stem and cap, when I turned the tap counter-clock wise the stem would start to come out. I was finally able to thread the stem so that turning the tap handle wouldn't take the stem out. However, the faucet still leaks. Worse yet, when I turn the tap on water comes out from the stem (where the seat is). Not a lot, but it does come out. When I turn tap off, water doesn't come from the stem, but it still leaks. What could this be? Can I assume that because I was able to insert the new seat that it is the right size? Worst of all, the old seat fell in the area behind the tiles I was worried about. Thanks