New to motorhome ownership water problem , help needed

I have just purchased a hymer 644 fitted with the electric gas heater.

The problem is that the water system seems to be draining back into the tank, on opening the cold tap and venting out the air I get water flow. Then returning to the tap after say a minute it's back to square on a again full of air and no flow.

Also the hot is the same, followed the instructions vented out bought hot taps and ran the heater the water seems to heat but only when the fan is running also.

No water is running out of the van and the taps located in the tank in the rear garage are all closed.

It seems it needs an non return valve or something to stop the water returning to the tank, I opened the tank and removed the pump when you turn off a tap the water runs straight back through the pump into the holding tank.

What do I need to check and were is it located.

Help please.

I have a non return valve fitted to the cold supply near the truma heater/boiler, you can get them on ebay cheap enough, but is that the problem, has the dump valve been reset and is the breather valve given up the ghost? Is it a carver or truma system.

If you put on your profile where you are from (county is enough) we could point you towards a dealer or repair specialist in your area.

The dump valve is normally near the boiler, are you in the UK.

Good Morning,
Might i suggest you check the seal from the pump outlet to the tap pipes if there is air getting in or when the pressure is turned off - the water just runs back out again?

You'd wonder where the air is getting in... Are there any dripping taps anywhere in your camper? When the 12v pump is switched on, does the pump cycle every so often even though you're not using water?



We had an airlock in our camper last year and it kinda displayed similar issues you're seeing, but I'm not sure if it is exactly the same issue.... but I'll throw my 2c in anyway ..... The only way I was able to expel all of the air out of our system at the time was to bring a garden hose into the camper and connect the end of the garden hose to the tap in the kitchen sink. With the 12v water pump switched off, I opened both knobs in the kitchen tap, then opened the knobs in every other tap in the camper and then went outside and turned on the mains water (gently) to get the pressurised water to push the air out of the system. It worked a treat and solved our problem.

We have a "city water" connection on the outside of our camper that allows us to hook up directly to mains water when on a serviced site, but it wasn't working at that particular time. If you have a "city water" connection on your Hymer, then this would be the best way to expel the air from your system...

If you've purged all of the air out of your system, and the issue persists, then I'd be checking the taps and NRV's for leaks, then I'd start poking around in the back of cabinets and under seats to look for leaking compression fittings at every pipe connection.

Hopefully it's only an air lock in your system...

Here's a simple diagram I found of a water circuit in a typical camper to help visualise the system -