Hello all,
I have a quick plumbing question. I just bought an old house with
a very new 40 gallon gas water heater (mfg 2006). The hot water seems
very abundant at all the faucets. However, after running a hot shower
for approximately 4 or 5 minutes, the water gradually gets cooler and
cooler. Eventually, it gets uncomfortable and I can tap the knob (its
a single knob for temperature control) slightly warmer and it suddenly
is pretty much right back up to temperature for a short period of
time. After getting out of the shower, the hot water coming out of the
faucet at the sink is very warm but certainly not as hot as it usually
gets. I replaced the shower value with a new pressure balancing Kohler
unit, but it exhibits the same problem. So two valves are doing the
same thing. I did some research and though that it might be a dip tube
problem in the water heater. But I'm not so sure since I CAN get the
shower back up to temp at least for a minute or so and its a new
heater. Its seems very mysterious to me and I would appreciate any
help you can provide. Thanks in advance.

Zach