I have a spare filter if you need one desperately. I'll have it with me the Piggy. At present I have taken the core out of the old one on the basis that I use fresh water daily so what's the point of the filter? The non-return valves are horrid to change. They are plastic (if it's like mine) and you need to get all the small-bore fittings off to get a tight-fitting socket on otherwise the corners round off and then you ARE stymied. I found a bloke in Nottingham who would do the parts cheap - but mine still dribbles if you run the heater before you have attached the drop-in pump.

The bloke wot does the bits on my van that I can't took another look at mine (and it still dribbles as aforesaid) and he had to get at it by removing the Carver II fitting panel from the van (from the outside) to put it on a bench to dismantle. I want to try adding another non-return in the pipe. That seemed to work fine on the old van but the pipe diameters are different.

If you put the water container above the inlet socket, then water will not drain out, but siphon in, and if you then have hot water it is definitely the non-return valve (or maybe the pump) that is the problem.

I also have a very hi capacity pump I want to try, to get a better shower, but some people are telling me that if I overdo it I could blow all the seals in the Carver II and possibly throughout the water system. The hicap in my old van never did that though, on a much older system. If it works you can have my old one to try out if you like.