Don Y wrote:
On 11/20/2015 9:03 PM, John G wrote:

Just had my gas storage heater replaced because the tank was leaking.
both the old and the new have a pressure relief valve on the tank and the
correct proceduere is to lift the lever every month or so and release
a little
to flush out the salts. In normal use it opens each time water is used to
relaease the pressure.
This quite simple and is the standard way here in AUS.

The "relief valve" (driven by temperature and/or pressure) on
US water heaters typically doesn't operate until ~150psi.
Letting the water system sit at 150psi places undue strain
on appliances, fixtures, etc. (most are designed for 80psi)

Operating the system at a consistent, lower pressure
makes life easier for those appliances -- as well as
helps to conserve water (higher pressure implies higher
flow rates; usually, folks don't finely tune the faucet
for "ideal" flow rate but, rather, get the right temperature
and an approximate rate)

Most folks don't do *any* maintenance on their water
heaters until they fail (at which time, its hardly
called "maintenance"! : ). Depending on the characteristics
of your water supply and your "maintenance history", opening
*any* valve on the water heater can leave you with a new
problem: a valve that doesn't reseal completely.

[I'm always leary of replacing either the TPR valve or the
drain as they both thread into glass bottles...]

Best hot water tank I had is Sears Power Miser 9. Going on
16th year w/o a single problem. Knock the wood now.