I started having problems with my hot water heater a month or so ago. Basically, the hot water would just run out much more quickly than before. I had someone out to look at it and they tried replacing the thermostats and it only made things worse. The tank was about 20 years old so I just went ahead and replaced it with a (slightly larger) tank.
However, my problems now are still worse than they were before. Basically, in order to get the water hot enough to take a shower (and I don't take really hot showers) I have to turn the knob about 80% of the way towards the hot side, whereas before I only had to turn it about 50% of the way. Then, once it's there, the temperature only stats constant for about 2 minutes until it starts getting cold and I have to turn the knob further towards hot. Needless to say, I hit the end fairly quickly and spend most of my shower in lukewarm (at best) water. With my old hot water heater (and every one I've ever used before), the water temperature would stay constant for about 15-20 minutes before I would have to adjust the knob at all if it took that long (this was pre-problem). The new tank is also 10 gallons larger than the old one, so it doesn't make sense to me that it would produce so much less hot water.
I checked the thermostats and they were set on 115, which seems low compared to what I've read online. I cranked both thermostats up to 135 and it helped a little bit, but not much. I know when I call them they're going to give me the "well sir it's only a 40 gallon tank it's not going to give you hot water for an hour" run-around, so I was wondering if any of the knowledgeable folks around here had any insight on the matter?