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Old 05-31-2014, 06:17 PM   #1
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perplexing water pump issue

I'm the non-mechanically inclined newbie owner of a 2011 19' FC, but this seems weird:

I filled our freshwater tank after our last trip (our emergency water supply in a crisis) and all seemed well. The next day I noticed some water slowly dripping out of the water fill area. Assuming I had over-filled the tank I ran some water into the sink to lower to volume in the tank. Over the next several days I noticed the same thing, usually occurring as the temps increased. It would drip for a while, then stop (drip spot in driveway would dry out).
It's been 1 1/2 weeks since I filled the tank. It is still occasionally dripping and I decided to investigate further. When I turned on the pump it initially ran for much longer than usual. I actually turned off the pump because I was concerned about where the water was going. There are no internal or external indications of a leak.
While I was fiddling around, I turned on the faucets with the pump switched off. I ran the kitchen faucet for 30-plus seconds at full pressure before turning it off. Then turned on vanity faucet for another 20 seconds before turning that one off.
Is the pump over-pressurizing the lines? Is there some strange way the water can create a siphon? Why is water continuing to drip out the external overflow screen near the fresh water fill? Should I continue to run the faucets to see how long they'll run before they depressurize?
Has anyone else experienced this?

Meg
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Old 05-31-2014, 06:48 PM   #2
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Hi,

Water will expand when heated. Your putting in ground or tap water at 50 degrees. It will expand as it heats up to air temp of 70 ish. causing the drip outside at the fill. Your not level will also cause the drip at the fill.


The hot water tank is suppost to have an air bubble in it to take care of expansion. Lift the pop off on the tank and let it snap back down to let some water out.
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Old 05-31-2014, 06:49 PM   #3
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You have got a good one there.

First off you are seeing water flow from both sides of the pump. The tank is expelling water through the fill port. The faucets can flow water for a prolonged period of time without the pump.

In short you are clearly defying the laws of physic.

Even if you filled the tank to the brim and let it sit in a warming temperature water does not expand with temperature rise until it approaches boiling temperature.

Unless there was an accumulator installed beyound the pump the pressure in the lines without the pump should only last a few seconds. Even with an accumulator that would only be 5 or 10 seconds depending on the size of the accumulator.

I don't have an answer to either issue but will clearly watch to see if there is one.
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Old 05-31-2014, 06:53 PM   #4
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perplexing water pump issue

My guess is that air is getting into the hot water system when parked for extended periods and the contents of the hot water heater are draining back into the fresh water tank.

This would explain the drip and the extended pump time when you first turn the pump on as the hot water tank is refilled.

The air could get in from a number of places, a tiny leak at a service valve or a leaking hot water heater pressure relief valve.
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Old 05-31-2014, 06:54 PM   #5
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If you have the city water hooked up the cause is a bad check valve in the pump that is allowing water to flow back through the pump and into the fresh water tank. There are other threads about this.
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Old 05-31-2014, 06:57 PM   #6
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perplexing water pump issue

My above answer assumes that city water is not connected, and that the pump check valve is seeping back to the tank.
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Old 05-31-2014, 07:05 PM   #7
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Lets think a little further.

If your trailer was tilted so the fill port was on the lower side of the trailer when you filled it that would create an air pocket on the high side of the tank. That air could be expanded by temperature rise and force water up the fill tube.

If for some reason you had not filled the hot water heater, by drawing water from a hot water faucet till ALL the air was out of the hot water heater you would have an air head on the system and that would cause a prolonged water flow. But I am assuming you used hot water on your last trip.
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Old 05-31-2014, 07:05 PM   #8
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"Even if you filled the tank to the brim and let it sit in a warming temperature water does not expand with temperature rise until it approaches boiling temperature."

Sorry, but this is wrong. Water will expand at any temp rise. FYI 30 years a pipefitter.

There is no accumulator on new Airstreams and they don't recommend them. The air bubble in the hot water tank takes the place of it.

" If you have the city water hooked up the cause is a bad check valve in the pump that is allowing water to flow back through the pump and into the fresh water tank. There are other threads about this."

This would only have water going in a loop replacing water with water.
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Old 05-31-2014, 08:21 PM   #9
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IMO it is almost certain that the water from the hot water tank is slowly running back into the fresh water tank.

This creates a situation where there is no expansion space for the water as it expands in the day heat and the water is slowly expelled from the fresh water fill that may well be higher than the hot water tank....

I guess this is kind of a guess since I can't be there to further investigate, but hey, it sounds plausible no?
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Old 05-31-2014, 08:28 PM   #10
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Quote:
Originally Posted by J. Morgan View Post
IMO it is almost certain that the water from the hot water tank is slowly running back into the fresh water tank.

This creates a situation where there is no expansion space for the water as it expands in the day heat and the water is slowly expelled from the fresh water fill that may well be higher than the hot water tank....

I guess this is kind of a guess since I can't be there to further investigate, but hey, it sounds plausible no?

Except that there is a check value to keep pressure out of the non pressurized water poly water tank. The hot water tank expansion would be seen as a leaks at the facets.

I do kind of like the idea about the trailer not being level and there could be an air bubble in the fresh water tank. Air does expand at a much large rate than water.
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Old 05-31-2014, 08:31 PM   #11
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perplexing water pump issue

Assuming that the check valve isn't seeping or leaking.......

Where else would what might seem to be gallons of water come from but from the hot water tank?

Where else might gallons of water go when the op first turns the pump on ?

Air can get into a line to vent fluid withdrawal where water might not pass.

If my theory "holds water", I would first suspect the hot water safety relief valve as venting air to the tank.

A little crud in the safety valve, and a little crud in the pump check valve..... And presto, water from the hot water heater floods the fresh water tank over time.
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Old 05-31-2014, 08:37 PM   #12
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There is no check valve as such. The pump ax as the check.

As for the expansion of water due to temperature rise that is Too small to measure let alone have an effect. Yes water will expand do to rise or fall in temperature from 3.87 degrees C.
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Old 05-31-2014, 08:39 PM   #13
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Technicality, the pump acts as a check valve, same difference.
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Old 05-31-2014, 08:40 PM   #14
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perplexing water pump issue

Gravity moves the water from the heater to the tank, and then thermal expansion expelled the water out the fill.

Remember, the freshwater tank itself will expand and contract some too.
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