I have been concerned about having to put the grey water tank under the vehicle due to the possibility of it freezing in winter.
I have now found a couple of methods that will make this unnecessary.The first is a dedicated pump. FloJet Waste Water Pump
The second is a fully enclosed. Saniflow waste pump
The FloJet is smaller and cheaper but the Saniflow is designed to fit under the shower tray and also as a separate inlet for the sink which will mean it empties quicker. The FloJet is 12V while the Saniflow is 240V.
I get the Bus tomorrow and will be able to start looking at the layout properly at which point I will decide which one to get.
With one of these pumps installed I can keep the Grey water tank inside the van ensuring that I do not have any freezing issues over this winter. I am hoping to be able to situate the grey tank under the sink.
The power to the pump itself will be linked into the light that I will have in the shower. So when I switch the light on the pump will come on.