I have a Rheem Steller natural gas hot water service. There is a continuous dribble of water from the pressure valve overflow, even when the heater is not heating. I have tried easing the valve a few times but the water continues to dribble (probably filling a cup in about one or two minutes). The pressure valve is a HT55 (AS1357-1) with 1400 kpa pressure and temperature of 99c. I want to change the valve. Do I turn it down to just the pilot light, turn off the water and just unscrew and then screw in the new valve? It appears a simple operation to undertake but I don't want to end up scalded because of not knowing what I am doing. Regards, Greg Boland

over heating possible bad gas control valve , relief valve bad or water pressure too high or overheating will cause it to leak also lack of thermal expansion tank

Sell it on ebay.

A simple chip change will not convert because the orifice for each gas is different, the gas control valve is different, NG and LP gas each burn at different temperatures and pressures... with propane having higher temps and pressures.

Don't buy tankless computers and expect trouble-free installation and water heating bliss afterwards.
Read the manual for maintenance requirements, and look at the parts sheet and ask yourself how such a complex machine will simply balance and monitor water flow, water pressure, incoming and outgoing water temperatures, gas pressures, vent pressures, gas quality, gas pressures, while connected to water, gas, venting and electric systems inside your home which each have innumerable problems on their own.
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

Install tank type heater for around $400 and live worry free.
Avoid Rheem products since they do not post service manuals.
http://waterheatertimer.org/Which-is-best-gas-water-heater.html

Gene
h

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

1) Rheem does not post service manuals.
Call Rheem and ask why, since the other big manufacturers, AO Smith and Bradford White do post service manuals.

2) You need new propane gas control valve, and matching combustion parts to fit existing tank.
http://waterheatertimer.org/pdf/Rheem-Water-Heater-parts-catalog.pdf
http://waterheatertimer.org/images/IMG_1826-LP-burner-450.jpg

3) Rheem does not recommend changing gas type, especially from natural gas to LPG.
LPG is higher pressure, and burns much hotter and requires cast iron burner, unlike the lighter-weight metal used for Natural gas burner.
The manifold tube and thermocouple must match the gas control valve, and gas-type and have correct thread for propane.
The combustion chamber and heat transfer surface can also be heavier metal for propane heaters.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

1) You want the truth: Forget tankless.
There are many tankless water heaters with insoluble problems.
And endless problems.
Rheem knows it.

2) Do you really expect your home computer to work flawless after replacing motherboard?
Get your money back from Rheem, or get a full replacement.

3) OR fix water heater yourself today: Install tank-type gas water heater for $350 from local box store.
FYI: Do not buy Rheem, Richmond, Ruud, GE as these units from Rheem have problems that require service technicians.
Instead buy Whirlpool, American, State, Craftmaster, Reliance, Kenmore, as these units from AO Smith have fewer problems and can be repaired by homeowner using simple part replacement.
http://waterheatertimer.org/How-to-install-gas-water-heater.html

4) Copy following link for troubleshoot resources, and possible manual for Rheem, Richmond, Paloma water heaters:
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Before calling service technician, open following link for Rheem troubleshooting resources.
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

List of causes MIGHT include one of following:
Bad household circuit breaker that powers electronics, or loose wire inside outlet where tankless plugs in.
Tankless fuses and control board.
Water flow rate too low. Minimum .8 gallon required (depending on model)
Tankless inlet filter clogged.
Household aerators clogged at faucets.
Crossover at single-handled faucet
If installed, there can be crossover at mixing valve.
Faulty household check valve, including check valve on re-circulation system if that system is installed.
Restriction in household water line, such as clog at elbow.
Unequal pressure in household hot and cold lines, caused by restriction in hot line. When single-handled faucet turns on, the cold water pressure is higher so hot does not flow and tankless will not turn on.
Loose wire connection inside tankless.
Unit temperature set too high.
Unit temperature set too low.
Water temperature is very hot coming out of tap, so more cold is added, but that reduces amount of hot water flow, so tankless turns off because flow rate is too low.
On some tankless, if water is preheated by solar or other indirect source, the burner will not activate.
High mineral content in water > delime tankless yearly
Misaligned temperature sensor
Low gas pressure. Wrong type of gas. Undersized gas line.
Too many faucets on at same time.
Faulty tankless water valve. Water valve stuck.
Fluctuating household water pressure, for example MUD and PUD district water pressure problems or water well pressure.
Faulty household pressure reducing/regulating valve if installed.
Faulty household pressure tank, if installed -or- pressure tank needs to be installed.

http://www.greatergoods.com/store/energy-savers/tankless-water-heaters/rheem-rtg-74-dvn-natural-gas-tankless-water-heater/prod_386.html
manual above.
I professionally recommend that you get a Plumber/Gasfitter, to check this over, as this isn't usual, and I wonder if there are not "Other" problems too... with anything that uses Gas one has a responsibility to the entire family to have it professionally checked over, in my humble view..

Sounds like you may have the wrong type gas going to this? Is this an LP gas or natural gas unit? will say on label. Natural gas units run only on natural gas ditto for LP. Could be issue with manifold pressure settings. Could be obstruction in exchanger or vent. Have a authorized technician check over

If by the hot water over flow valve you are refering to the T&P valve. It is activated by high temp. or high pressure. It is possible that when you flushed the lines it caused this to open. It is also common for these once open to get a little debris in them and cause them to continue to leak. Sometimes you can open and close them a few times and get them to reseal. Other times you have to replace them. Hope this helps.

if your on a private well, it sounds as though your loosing enough water pressure to shut the heater off,.(which is right before the water pump comes on),....tankless heaters turn on by sensing water flow, and of course off when flo stops,......water pressure tanks often need to be re-charged with air for pressure to stay even,....does your water pressure fluctuate?