Reliance propane water heater. Water too hot, even at lowest setting. Reliance sent new thermostat, same thing! Now they tell me it's because we don't use enough hot water! Is it possible?

SOURCE: takes too long for hot water.

You need a recirculating line. You will have to hire a plumber to run a water line from the farthest fixture or to the fixture you are concerned about on the hot side and return it back to the water heater. this will cause hot water to constantly run throught the hot water line (via the recirculating line) and when you want to draw water from the fixture, you will already have hot water right at the line.
I know this works with standard tank water heaters, but it is a lil trickier with rinnai units(but very possible) if your plumber pleads the 5th and tries to sell you another unit call the Rinnai manufacturerand ask them how.

SOURCE: 12-year old Rheem residential single-thermostat

TIME TO REPLACE TODAYS ARE MORE EFFICIENT

Sean Lavelle

• 21 Answers
• Posted on Jan 26, 2010

SOURCE: Water Too Hot

needs new thermostat(s) If the whole tank is heating( next time it trips, before using any hot water check the lower tank thru the lower element access(breaker off) If the lower tank is hot-you need a new lower thermostat. if just the upper part of the tank is heating -you need an upper thermostat.

SOURCE: need to empty reliance 501 hot water heater how?

1) Shut the breaker off to it at the panel. 2) Hook a hose up to it (the bottom has a drain). 3) Close the valve to the water heater (on the cold water supply). 4) Open drain on the bottom of water heater. 5) Open the relief valve to allow air into the tank (it won't drain otherwise - think if you put your finger on one end of a straw - the liquid stays in until you let go). Why are you draining it by the way?

SOURCE: how to change a thermostat on reliance 606 hot

I wrote a page for changing water heater thermostat.
The photos take you through step-by-step
I recommend replacing both upper and lower thermostats so it eliminates thermostats as possible cause if water heater keeps overheating.
http://waterheatertimer.org/How-to-replace-thermostat-on-electric-water-heater.html

The Reliance 606 manual shows your water heater uses generic upper and lower thermostats from hardware store.
http://www.reliancewaterheaters.com/lit/om/manuals/185761-000.pdf

Likely the thermostat will solve the problem:
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html