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Old 03-17-2019, 07:57 PM   #1
Junior Member
Brand: Thor Motor Coach
State: California
Posts: 3
THOR #14705
Fresh water pump runs continuously

Hello All,

After filling the freshwater holding tank of our 2017 Thor Outlaw the freshwater pump is running continuously.

This happened during our maiden voyage. Did I do something wrong? I have been able to turn the pump off manually.

Any help would be appreciated.

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Old 03-17-2019, 08:15 PM   #2
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Miramar Owner's Avatar
Brand: Thor Motor Coach
Model: Miramar 34.4
State: Iowa
Posts: 663
THOR #4488
The pumps works by building pressure. Many things can cause it to fail to build pressure, including a bad pump. But I would first look for the obvious. Are there any faucets or low point drains not completely closed...Any water under the RV.

You could have some debris stuck in the pump itself. Clean the screen filter near the inlet side of the pump then run the pump through several on/off cycles.

If none of this solves the problem it's most likely internal to the pump itself. Good luck.

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Old 03-17-2019, 08:29 PM   #3
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Brand: Thor Motor Coach
Model: 2013 ACE 30.1
State: Alberta
Posts: 1,011
THOR #2631
First, do you get water coming out of the faucets while the pump is running? Yes means at least the valves are open from fresh tank through the pump to at least one faucet. No water entering the low pressure side of the pump can cause continuous pump run. If water out the faucet is poor or sputtering at best you likely have a suction side air leak or plugged pump filter not allowing water into the pump. The in line pump filter (usually plastic body) is a great place to have a crack you canít see or a cap that is not sealing air out of the suction side of the pump.
On the pump output side make sure all faucets and low point drains are closed and there are no obvious leaks anywhere.....including the dog wash taps are closed. Did you fill the hot water tank (if equipped) and put the plug in the hot water tank (if you took it out over Winter)? Pump will run several minutes filling an empty hot water tank. Thatís a start at least.
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Old 03-17-2019, 10:06 PM   #4
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Brand: Thor Motor Coach
Model: Hurricane 31S
State: Texas
Posts: 1,670
THOR #6411
If you have an Anderson valve, do you have it in the NORMAL position.
Jim & Roy Davis
2016 Hurricane 31S
1961 Rampside in tow
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Old 03-18-2019, 12:13 AM   #5
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Brand: Thor Motor Coach
Model: Challenger 37LX
State: Maryland
Posts: 109
THOR #3920
As in my case, there could be a small leak somewhere. I kept hearing the pump run every 10-15 seconds. I knew all faucets were off so there had to be a drip. I began checking everywhere inside because I didn't want a water leak inside the motorhome. I did find it once I went outside. There was a connection up behind the water controls that did not have and plumbers tape or putty and after using a flashlight and mirror, I could see the slow drip. Only it didn't drip right down, it hit another line and just ran down perfect and out the hole where the sewer hose goes. I only caught it because I was in my yard checking things out. When we travel down the road, I really can't hear it, but my son noticed it while we were driving.
2017 Thor Challenger 37LX, Westward interior, Riverside paint job. Upgraded to 4 battery setup, Splendide 2100XC Washer/Dryer combo, Progressive Industries HW50 EMS, Heavy Duty Steering stabilizer, and TST TPMS 6+4 setup for tow vehicle . Member FMCA

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Old 03-18-2019, 11:59 AM   #6
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Brand: Thor Motor Coach
Model: THOR Chateua 35SF
State: Georgia
Posts: 4,022
THOR #11130
Not sure of the setup but mine has a 90 degree "gate valve" right between the tank and pump input (supply line). This may have been shut off during winterizing and never opened back. If you are getting water out of your faucets, this would not be the problem. Also, check the "plug" that you remove to attache your winterize input line...it may have not been reinstalled tight enough and allowing air to get sucked through a bit, causing pump to run all the time.
2018 THOR Chateau 35SF
Two Labs, Bugsie & Blondie
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Old 03-18-2019, 08:08 PM   #7
Brand: Thor Motor Coach
Model: Four Winds 35SK
State: Arizona
Posts: 38
THOR #14346
If the pump is running constantly then it kinda boils down to a few things. Its either sucking water and dumping it, or its sucking air and wont prime. First, as previously mentioned in the above posts, do you see any water anywhere? No, is this a new problem with no changes to the supply line from the tank? You did it just like every other time? No, well then it is probably not some sort of closed valve. If it aint sucking water, then it is the sucking air part. Loose coupling? Maybe but not likely. Does your pump have a small strainer with screen right in front of the pump? Possible clog? Finally, its possible the diaphragm pump could have failed.

Also, you said you filled the fresh water HOLDING TANK. I associate that with black. Think your "belt slipped" there. LOL. Mine does all the time. And of curse I know what you meant.

Good luck

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freshwater, holding tank, water pump

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