Cokie74 Posted March 27, 2017 Share Posted March 27, 2017 Hi All I have a 2003 Hymer B644 with a Truma C hot water and heating system. When I turn on the taps it takes a while for the water to at the tap (and shower). Pressure is fine when water does flow. When I turn off the taps there is a hissing from the vent pipe in the rear wheel arch and then when the taps are turned on again it takes a while for the water to flow. The frost protection valve is shut and no water is leaking. I have the water drained down for the winter but use the van all the time. I think it could be faulty non return valves on the inlet side and/or gunge build up? Does anyone have other ideas? Thanks Glenn Link to comment Share on other sites More sharing options...
Robbo Posted March 27, 2017 Share Posted March 27, 2017 Your symptoms sound very much like the non-return valve at the water tank isn't functioning properly. It is probably allowing water to drain back into the tank. Link to comment Share on other sites More sharing options...
Cokie74 Posted March 27, 2017 Author Share Posted March 27, 2017 Thanks Could it be a faulty frost protection valve as well? I can't see any non return valves but if the van was inclined I could see that the water could drain back through the frost protection. Regards Glenn Link to comment Share on other sites More sharing options...
Derek Uzzell Posted March 27, 2017 Share Posted March 27, 2017 Glenn The non-return valve Robbo mentions will normally be attached to (or integrated into) the submersible water-pump that will be hanging from a water-hose inside your Hymer’s fresh-water tank. Not sure about the hissing noise, but the non-return valve is definitely the prime suspect. If there’s no water leaking from beneath the vehicle, the anti-frost safety/drain valve should not be contributing to the problem. Link to comment Share on other sites More sharing options...
Robbo Posted March 27, 2017 Share Posted March 27, 2017 The non-return valve is a known problem with the Hymer style water delivery system. Suggest when you turn the tap off, you check if any water is trickling back into the tank. I don't know exactly where the non-return is located but assume it's on the outlet side of the submersible pump. I never had this problem with my Hymer, thankfully. If there isn't any water leaking under the van then I can't see that the dump valve is at fault. Edit - Derek overtook me in my reply :-D Link to comment Share on other sites More sharing options...
Cokie74 Posted March 27, 2017 Author Share Posted March 27, 2017 Hi Guys Located the NRV on the pump outlet and it appears to be the culprit. Off to get a new one this afternoon. Cheers for all your help. Regards Glenn Link to comment Share on other sites More sharing options...
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