eamarquardt wrote: Shouldn't the assembly be all abs or pvc an and appropriate glue used?
Gus
Sorry, I just used the term PVC, technically I don't know the difference, but whatever the proper plastic and glue is, make sure it is for potable water.
Nikwax,
I am sure others will chime in with good advice. I merely just looped the vent tube so that it arched up and higher than the tank. Then secured it pointing down and underneath the trailer. Provided that your fill tube is higher than the tank and relief hose.
My thoughts for my installation when filling the tank via a pressured hose, the tank will fill and overflow onto the ground. That's when I know it's filled. If you are more comfortable with making it air tight when not in use then put a simple valve on the end of that hose.
You will need an open relief valve when you fill it, and also the same relief will allow the water to flow when pumped during use. This will prevent a vacum in the tank. At the end of a trip, I open a separate drain valve and empty the tank. The next day I will close the drain valve when it's empty. Does that help?