I have had the embarrassment of loud a noise emitting from the water line whenever using mains pressure.
Problem turned out to be the plastic fitting that you connect the hose to at the water filling compartment, it has a small spring loaded valve inside that fails and creates the noise. The replacement part is $13 and requires a philips head screwdriver and large shifter or multi-grips to replace.
1) Remove the 6 screws that hold the cover one.
2) Rotate the fitting about 10 degrees in a clockwise direction to allow the fitting to be removed from the cover. (only comes out about 2cm)
3) Hold the large black plastic nut behind the plate and unscrew the noisy filler port and replace. (they are supplied with thread tape fitted)
4) Replace cover and relock the tab on the new filler.
All good noise is gone.
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Brian & Nada retired and > "Ready to live the Dream" Live in the Shire!
76 series V8 Landcrab with Jayco Starcraft Outback Poptop
Thanks, I had the same problem and replaced the connector and all was quiet when connected to mains however when I disconnected and was on the way home I stopped and turned on the pump for some water and lo and behold it kept pumping and the water was coming out of the mains intake??? I got home and I pulled off the new fitting and found the little valve was open as the "o" ring has partially come off and jammed the valve open. So I stopped off the mains intake but now the pump seems to take a while to reach pressure and when I turn the pump off and a tap on to let off the pressure the water keeps flowing slowly out of the tap??? It can't be gravity feed so must be acting like a siphon? Can anyone explain?