I have a four-year-old gas water heater that is acting a little
strange. Beginning a couple of years ago I noticed that once every
couple of months I'd be the first to take a shower but the water
wouldn't be very hot. In fact, I could turn the mixing valve all the
way to hot and it still wouldn't be hot enough for my tastes. The next
day it would be back to normal.

Fast forward to now and the problem is occurring more often. I have the
temp set at "A", which I think is 130 degrees, and the water still
isn't nearly hot enough. It certainly isn't as hot as it usually is. I
should not be able to stand in the shower with it all the way on hot
without being extremely uncomfortable.

Any idea what the problem could be? I'm obviously a newbie with this
stuff so be gentle.

Many thanks,
John