Model no 101160 water constantly leaking water from over flow unit about 15 years old its a rheem hot water system

Water heaters by Rheem have not changed that much over the years. the link below will give you some good information about electric water heaters in general. As water heaters age, the heating element will lose efficiency due to deposits and general build-up of minerals in the tank. Turning up the temp may not be a good idea since the problem is actually caused by a coating on the element. Also make sure that cold water is not bleeding into shower valves thru other single lever faucets. While shower is running, listen to and feel the water lines connected to sink faucets in other rooms for water transferring thru valve. You can actually hear water running at faucet while shower is on if faulty. If other vaucet valves are leaking thru, repair those first before you do anything to the water heater as that is cause of loss of hot water. Good luck.




http://www.rheem.com.au/images/pdf/owners_dom-elec_121996C_0707.pdf

If you are paying for your water, I litre per hour is going to cost you. If the unit is 15 years old, I would seroiusly comsider replacing it buy, if it's just a bad valve, you could try to replace it. If it is cracked at the threads, it's time to replace it for sure.
Dave

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.

If you are on city water and your inlet to your house has a back flow preventer this could be you problem.if so theres an expansion tank that can be installed on the cold water line,after you water warms up theres no room for expansion and the relief valve goes off at 150 psi

valve is bad boy a new one and install

According to the symtoms...sounds like you have a problem with the flow control valve. If less than 3 yrs old, contact Rheem Customer Support at (800-432-8373) and they can an authorized tech in your area to service the unit.

If the unit is out of warranty, I reccommend you still call customer support to find a local technician. Unless you're highly technical/mechanical, this is not a problem you should attempt yourself.

Thanks for trying Fixya.com

Mike...

boiler type? Combi,standard,if your boiler is a combi the non return valve onto your heating line may be defective thus hot water slippng back through cold line best of luck

About the only device in that heater that could cause the noise you describe is an electrically operated valve that controls water flow. Rheem is a better-than-average company so I would give them a call and describe your problem to them; I'll bet that they will be glad to tell you which part you need and supply it to you.
We had a heat pump system from Rheem that needed only the replacement of one large relay and the outside unit fan motor during more than 25 years of service and is still operating at age 30 in our former home.

It could just be a leak around the threads of the connection of the pipe nipple in the hot water outlet. If so, you'll have to take out the one there now and replace it with a new one.