hot water runs hot then cold

Do you have hydronic heating or a standard hot water heater..Your coach could have either one...If hydronic, make sure water pressure is 55 or less and you are using diesel burner...also check your outside shower and make sure the water isn't on with the shower blocked..that mixes the water in some brands...

It could also be the water heater bypass valve is still open.

The water heater bypass valve being open and a shower being turned on at the tap but turned off at the shower heat (which seems to come up more frequently with the outside shower) are the typical causes of the symptoms you describe. They all allow unheated water to flow into the hot water lines along with the heated water.

...

DO you have an Atwood XT water heater......they use a mixing valve.
Heat the water very hot (160*F) then mix it with cold to control output temp (130*F)

Mixing valve gets clogged...water can come out Hot/Cold.



SO you have several options/choices/issues.

Post which water heater you have that is being used.

Another thing that will cause it is if your outside shower is turned on but shut off at the shower head. I did it last year, used the outside shower, shut it off at the head but didn't turn the valves off. Luckily, I remember to check it after just a few minutes and didn't have to suffer very long.

DrewE wrote:
It could also be the water heater bypass valve is still open.

The water heater bypass valve being open and a shower being turned on at the tap but turned off at the shower heat (which seems to come up more frequently with the outside shower) are the typical causes of the symptoms you describe. They all allow unheated water to flow into the hot water lines along with the heated water.

+1 Seen it many times

fourmat wrote:

DrewE wrote:
It could also be the water heater bypass valve is still open.

The water heater bypass valve being open and a shower being turned on at the tap but turned off at the shower heat (which seems to come up more frequently with the outside shower) are the typical causes of the symptoms you describe. They all allow unheated water to flow into the hot water lines along with the heated water.

+1 Seen it many times

My bet as well. Been there done that.

bullydogs1 wrote:
...If hydronic, make sure water pressure is 55 or less and you are using diesel burner...

Don't need the burner if driving. The engine warms the water automatically when running.

Water heater bypass is still open.

How Dun wrote:
We left the Midwest this morning with a winterized 2008 Newmar Dutch Star. We are far enough South to have water. The problem is the hot water in running from the faucet first hot and then cold. I have tried everything I can think of and still am not getting hot water only. What am I doing or not doing and what can be the problem? Thanks for your help.

Well..........

Find anything?