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Open Roads Forum  >  Tech Issues

 > Puzzling Plumbing Problem

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Dusty R

Charlotte Michigan 48813

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Posted: 06/07/22 06:25am Link  |  Quote  |  Print  |  Notify Moderator

I like to add a bladder type tank.

valhalla360

No paticular place.

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Posted: 06/07/22 06:38am Link  |  Quote  |  Print  |  Notify Moderator

wguss wrote:

It does have the feature of using the engine's hot water to also pre-heat the water in the water heater.


What temperature is your MH engine running at?

Normal engine temperatures are right around or just below boiling. If you are running hot, after a few hours driving, the water tank may be approaching boiling.

Is there any dripping from the pressure relief valve?


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wguss

So. California

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Posted: 06/07/22 07:47am Link  |  Quote  |  Print  |  Notify Moderator

Quote:

What temperature is your MH engine running at?

Is there any dripping from the pressure relief valve?


It's a V-10 on a F53 chassis. The temperature gauge never moves so I'm guessing around 195 degrees.

No dripping on the relief valve.

Grit dog

Black Diamond, WA

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Posted: 06/07/22 08:10am Link  |  Quote  |  Print  |  Notify Moderator

wguss wrote:

We usually turn on the water heater when we're a few minutes from stopping for the night. It does have the feature of using the engine's hot water to also pre-heat the water in the water heater.
It could certainly be a bad pressure gauge but when I attach the hose for city water or turn on the pump it shows 45 pounds each time. I can turn a valve to add water to the tank and it snaps back to 45 pounds when static pressure returns. I often cycle the water from the pump through the tank to get all the air out of the lines and once again the pressure gauge always reads 45 pounds.


So it does this without hot water turned “on”??
I’d suggest you change your routine until you find out what thing it is that you’re doing that causes this.


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dougrainer

Carrolton, Texas

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Posted: 06/07/22 08:30am Link  |  Quote  |  Print  |  Notify Moderator

Your problem is the Motoraid feature causing the excess heat of the water in the Heater tank and causing the pressure rise from the heat of the water. Try this before your next trip. Doug

PS, The Atwood pop off valve psi trip is 125 to 150

PRESSURE-TEMPERATURE RELIEF VALVE
Weeping or dripping of a pressure-temperature relief valve while the water heater is running DOES NOT mean it is
defective. This is normal expansion of water as it is heated in the closed water system of a recreation vehicle. The
Atwood water heater tank is designed with an internal air gap at the top of the tank to reduce the possibility of weeping
and dripping. In time, the expanding water will absorb this air. To replace the air follow these steps:
Step 1: Turn off water heater
Step 2: Turn off incoming water supply
Step 3: Open the closest hot water faucet in the coach
Step 4: Pull handle of pressure-temperature relief valve straight out and allow water to flow until it stops.
Step 5: Allow pressure-temperature relief valve to snap shut, turn on water supply and close faucet

Grit dog

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Posted: 06/07/22 11:24am Link  |  Quote  |  Print  |  Notify Moderator

^What he said.
And stop driving with your water pump on.

dougrainer

Carrolton, Texas

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Posted: 06/07/22 11:50am Link  |  Quote  |  Print  |  Notify Moderator

The cheapest and simplest fix is to just bypass the Motoraid. Doug

wguss

So. California

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Posted: 06/07/22 12:57pm Link  |  Quote  |  Print  |  Notify Moderator

Thank you, Doug. I will give that a try.

Bill

wguss

So. California

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Posted: 06/07/22 03:19pm Link  |  Quote  |  Print  |  Notify Moderator

Doug if you happen to come back to this thread I have one more question. If it was the expansion of the water from the motoraid that is causing the problem, why do you think the pressure gauge doesn't rise when the water heater is used when we're at rest overnight?

Thanks,
Bill

dougrainer

Carrolton, Texas

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Posted: 06/07/22 07:55pm Link  |  Quote  |  Print  |  Notify Moderator

wguss wrote:

Doug if you happen to come back to this thread I have one more question. If it was the expansion of the water from the motoraid that is causing the problem, why do you think the pressure gauge doesn't rise when the water heater is used when we're at rest overnight?

Thanks,
Bill

Simple, The WH tstat is 140 degrees. The Motoraid heats the water to almost 180 degrees in transit. There is NO tstat for the Motoraid function. So the water will get as hot as the engine coolant. That is why I suggested bypassing the motoraid. Remember, you NEVER thought you had this type problem until you installed the pressure gauge. Ignorance IS bliss. Kind of like a person with a watch KNOWS the time, but a person with more than 1 watch is never sure. Doug

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