Hot Water - Heats But Goes Cold Quickly

[MikeMarie]

We have a dual type water heater and both electric and AV gas heats the water properly. However, when we turn on the hot water tap it comes in hot but then goes cold. Then when we turn off the tap and then turn it on again the water is again hot for a short time before it runs cold. Any suggestions??

Mike...

[dickandlois]

Mike, if you have an outside wash area, make sure the hot and cold are turn off and not just the shower head. Cold and hot water can cross mix at these points. Also could be a problem at the mixing valve on back of the water heater, where cold and hot water mix to set the temperature.

Rich.

[desertdeals69]

You might check you winter storage valves.

[aztec7fan]

You might check you winter storage valves.

Yes, check the winterization/bypass valves. My coach has 3 next to the water heater and if they are set in the wrong configuration, the same thing will happen to me.

[ClayL]

Also a leaky winterizing diverter valve (used on one valve winterizing water heater systems) can cause the same symptoms. A leaky tempering valve also can do it.

if none of the things suggested by the other posters helps I would carefully get some hot water directly from the heater relief valve and check the temperature, It should be about 140 degrees unless you have a tempering valve then it should be about 160 degrees.

It the temp is right you have a cross feed between the hot and cold water somewhere.

[wolfe10]

All good advice.

Be aware that many water heaters also have a CHECK VALVE to prevent mixing of hot/cold due to slight pressure difference in the two sides of the system. They can go bad, particularly if the coach is used in an area with high mineral content in the water.