What are the modern/standard fittings for fresh and black tanks?

[josephpearce]

Given I am decent in composites I was thinking of building my own water and black water tanks, was it the standard fittings?

* For the fresh water tank I see the water pump I ordered takes 1/2, fittings so I was thinking of running 1/2 PEX. For the breather hose I assume I can use 1/2" PEX, for the line to fill it?

*For the black water tank, I assume I cut out the dimensions for the toilet to mount to. Use a 1/2" breather hose (too small?). For the outlet do I need a three inch fitting such as Uniseal Slip Fittings
I read somewhere about the waste water tank drain line screwing on, and it appears from the link above it is just a straight tube that comes out. Is there some other kind of fitting? And do I need another fitting where I ran rinse it out, or just use the same line that it drains from?

*For a grey water tank do I need another three inch outlet, or some smaller unit?

[purman]

some welding shops will plastic weld the fittings on for you. THats what I'm in the process of doing.

fresh water tank on my 68' has a filler cap on the outside that has a breather valve built in. So you just need the 1/2 inch connect to the pump if it fills the same as mine.

Black tank, there should be a pipe an 1 1/2 pipe or 1 1/4 pipe that runs out of it up to the roof, then you fitting to the drain pipe 2".

You could as I am planing to run the sewer line in a 2" to a valve on the side of the trailer where the grey tank pipe 1 1/4 " will also tie in. both will have a valve to stop either water or stuff going into the other line. Then there is just one hook up for both tanks.

Make sure you grey tank is towards the middle of the trailer. You don't want to much weight on the back. Mine is going between the axels.

[josephpearce]

Thanks Jason
I will keep the weight & balance in mind
For the line that fills your fresh water tank how large is that?
For the drainage of the grey/black you mention 2" at camping
World I see 3" hoses is 3" more common and is it threaded?
Thanks