Rheem 3805 Series Owner's Manual And Installation Instructions page 25

Noise inside water
heater or pipes.
P a g e | 23
during heating cycle
Blockage/debris inside
the TPR causing
continual leaking
High water supply
pressure
It is normal for slight
noise to be produced
while heating;
Sediment built-up at
bottom of cylinder
Lift the hand lever to discharge water, repeat. Replace
T&PR if necessary
Ask plumber to install pressure reduction valve.
Normal
Flush storage tank