Well we now have 3 trips under our belts in the cargo conversion and have run into an issue that I need to dig into before going out again. We have a sink drain which connects under the shower before heading through a hepvo valve, then drops 4" down underneath the camper to a tube to the grey tank mounted underneath the camper. When it is full driving home, we have the unfortunate experience of the grey tank water coming back up and into the low point drain (shower). Luckily it isn't a black tank and it is contained, but still unpleasant. How do others prevent this? Is a large check valve at the tank the solution?
A separate but related issue is for both my fresh water and grey tank air vent hoses are getting water up them and blocking air from being able to vent in. It may just be the way I've routed them and may just need to have get a 90 deg fitting so that the hose goes straight up instead of out then up.