A couple of things. I have two bathrooms and one of them, you cant really take a shower due to not enough hot water. You can shower for about 5-10 mins and the water is now warm, even when the handle is all the way on hot. Also a outdoor faucet has cool, then hot, then cold water coming out of it. I have checked the pipes and they are ran correctly, (hot-hot, cold to cold). My bathroom has no problem due to the kind of shower I have. This a new build and the water is not "hot" anywhere. I have the temp. on the tanks 130. Help Carolyn Stump
A few possible causes of the issue:
There are long runs of uninsulated cold and hot water pipes next to each other. The hot water pipe should be insulated to keep the water inside hot, and the parallel pipe cold. If you have any way to access the supply lines, insulate at least the hot water pipe. It is also possible that insulation in a wall or crawlspace, as opposed to pipe wrap, has been damaged. For example, if water has leaked into a wall, perhaps from an ice dam, it can cause wall insulation, particularly cellulose insulation, to clump and settle, and rodents can remove pipe insulation in a crawlspace.
Backflow from convection and from expansion of water in the hot water tank is pushing heated hot water backwards, into the cold water supply line, wasting that heat. Install a backflow preventer. A quick test for that issue is to partially throttle the water entering the heater, but do not reduce it to a trickle, let the tank overheat and be damaged! If water in the outside tap is now noticeably cooler, backflow is at least one culprit. Reopen the heater valve after testing!~