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Old 11-03-2018, 12:53 PM   #13
FlyingAroundRV
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Join Date: Oct 2017
Location: Brisbane Australia
Posts: 708
Hi Nomadicchefs:
The non return valve is a spring loaded plunger inside the pump head. It holds the pressure in your water system until you turn on a tap or flush the toilet. Without a non return valve, the pump would have to run all the time to maintain the pressure in the lines.
Also, when these pumps are used in RVs, the city water connection T's into the output line of the water pump. If the pump didn't have a non return valve, the city water would flow backwards through the pump into the fresh water tank and eventually overflow it.
The city water input pushes backwards against the non return valve in the pump and with enough pressure, can jam the valve. That's why I always reccommend that that people use a regulator and set it to not too much higher than the pump's rated output pressure.
Edit: Since the non return valve is in the output flow path of the pump, if that valve jams, the pump won't be able to move water from the fresh water tank into the plumbing system.
Ask me how I know.
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Scott
2015 F250 2WD Crew Cab
2018 Outback 272UFL

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