Hi Geoff We have a grey water tank in our Kedron. You might want to consider installing a couple of HepVo valves somewhere in the inlet lines into the tank, these are a one way valve that prevent any smells, discharge etc coming back up into the plumbing system and into your caravan. You can buy them through Reece Plumbing or some other places. Incidentally, our Kedron was the first to have grey water tank, which I designed, installed at the build stage, and is the system now used by Kedron. Well done. Pete