r3rjr wrote:

Sine the self-install of a short 40 gallon gas water tank....
Everytime I use the cold water in the house, every faucet, I get about
15-20 seconds of hot water. It starts off cold, then warm/hot, then
cold. This happens during winter and summer, so I can rule out the
furnace warming the pipes.

The copper pipes go directly to the water tank... could I be missing a
backflow valve? or something in that effect? The water lines are not
touching, nor are they touching the exhaust.

Thanks for any advice.

r3rjr

Often, thermal expansion will push hot water out of the tank,
into the cold supply pipe. Then, drawing water from the
cold pipe for a fixture will introduce that heated water.
Most noticeable if the water heater only has a short drop
off the main Cold line.

There are special nipples to be installed on the heater
inlet/outlet. They are called "Heat Trap" nipples and have
a small ball check restrictor built in. Maybe the old tank
had them.

Jim