OK, I am a general fix it guy, but I have no experience with hot water heaters (it's electric) specifically. I am not even really clear on how they work actually. Basically we had one in this old '77 single wide mobile home go it and leak all over. This was while I was away so my wife's loser son (he is handy if he isn't too stoned or drunk to bother; and she is the first to admit he is a loser) got one from another old mobile home and put it in and it's been fine for almost 4 years. Now though all of a sudden it still heats water, still as hot as ever, but it is as if the capacity has been cut to less than 1/4 of what it was and this is overnight. Now I imagine it is some sort of thermostat that is falsely telling it that it is full and all to the right temperature, but as I have already said, I only have the vaguest notion of how they must work, so any help will be appreciated. P.S. It has no identifying information on it and access is extremely limited in the tiny hole it lives in. I can have some pictures if someone told me what to get a pic of. Let me know and I will be grateful for any help I can get.