hot water runs hot then cold

[How_Dun]

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.

[BigSkyBob]

I removed my mixing valve and soaked it in CLR for a day then re-installed it. Been working great for 4 years. Probably due for another cleaning soon.

[tinkerer]

My coach had the same problem and I traced it to the Watts mixing valve. It was soldered so you could adjust it, I knocked the solder out and had my wife stand by the sink with a thermometer while I adjusted to the proper temperature. Been working good for about 5 years now. If you feel that's to risky I would replace the mixing valve.:)

[How_Dun]

It started working on own. Road conditions shook it loose. thanks for all your help.

[Old-Biscuit]

How Dun wrote:
Old biscuit called it. We have the Atwood XT with mixing valve. Can it
be repaired or must it be replaced ?

It can be soaked in CLR....sometimes that works, most times not so much

You can replace with OEM roughly $145...LINK

Do an Internet Search for a mixing valve.
Your OEM one uses 1/2" and is set for 130*F output

OR
Remove it completely.
Just change plumbing to COLD water IN (Bottom) and HOT water OUT (Top
Then change normal t-stat form the OEM 160*F to the 140*F t-stat used on all other models.(Atwood 91447)
Will need to change connection on brown wire from t-stat to a spade connector....XT uses a PIN connector

Removing it, changing plumbing (easy) and changing to lower temp t-stat is cheapest option AND no more mixing valve to plug up.

Downside......your 10 gallon water heater that was equivalent to a 16 gallon WH due to the higher water temp is now just a regular 10 gallon WH-------BUT no more mixing valve issues

[dougrainer]

How Dun wrote:
Old biscuit called it. We have the Atwood XT with mixing valve. Can it
be repaired or must it be replaced ?

They are better replaced. I doubt you could clean one out and then get the mixing valve to function correctly. The purpose of the XT series with the Mixing valve is to produce 16 gallons of hot water from a 10 gallon tank. DO NOT REMOVE IT. As Jetcare stated you will have extremely HOT water without the mixing valve. The normal temp of a RV water heater is 130 degrees. As Jetcare stated, the XT produces 160/170 degree water which is way above scalding temp. The Mixing valve takes that extreme hot water and mixes it with cold to produce 130 degree water output. Doug

[jetcare]

kalsbeek wrote:
Do not repair or replace it. They are a disaster and useless.
Just remove it out of the plumbing and go direct. We did this
6 years ago and never a problem.

This is a very bad idea. The water temperature in this XT water heater is 155-160 degrees. It will cause serious skin burns in a matter of seconds.

[kalsbeek]

Do not repair or replace it. They are a disaster and useless.
Just remove it out of the plumbing and go direct. We did this
6 years ago and never a problem.

[How_Dun]

Old biscuit called it. We have the Atwood XT with mixing valve. Can it
be repaired or must it be replaced ?

[Old-Biscuit]

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?

[Effy]

Water heater bypass is still open.

[Blaster_Man]

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.

[Terryallan]

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.

[fourmat]

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

[Tinstar]

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.