Hi all, Greg here - as indicated, when I connect to mains water it simply bypasses and pours out of a short drain tube under the van- any ideas what the issue is -TIA

Blocked tank breather perhaps? Hose come off under van?

Thanks joda, my understanding is that the mains water feeds straight into vans water system bypassing the tanks altogether, or maybe I've got it wrong

Stenno2,

I could only see the first and second of your postings in this thread. Not much information for people to elaborate on. Do you have any more information or a photo?
On my Jayco, all the water lines are visible if I go under the van to follow the pipe network around. Is your system working when the water goes on the ground from under the van? Presumably you have looked under the van for leaking or disconnected pipes?

In my van, Jayco did not fit a Non Return Valve (NRV) on the delivery pipe from the pump. They thought the pump would act as a NRV. It did for a while but with high pressure town water supplies, that method fails and water flows back into the water tanks. My water tank fill pipes overflowed as they are slightly lower than the breather pipes. I fitted a NRV afterwards. If there is Non Return problem, and the breather pipes are lower than the tank fill pipes are lower than the fill pipe, some water could go on the ground while the system is connected to town water.

Thanks Watsea. The tanks fill fine using each of the filler holes and the systems all work fine off the tanks, it is only when I connect the mains water so I can run off this instead of the tanks that this bypass occurs. I have checked the piping underneath and where the water is pouring out is a short tube about 30cms long and does not appear to be disconnected from anything else. I haven't actually checked to see if the internal systems are working as the volume of water pouring out seems to match the mains water flow. I suspect that you may be onto something with the NRV as I was unable to see anything like that inline.