Thickwalled rotomolded PE is the recommended material for waste holding. And Ronco Plastics Ronco Plastics marine Tanks
(no relation to the VegoMatic Ronco) is your best source for a tank. They make TOP quality thick-walled water
and waste tanks
for a very reasonable price
and have more than 400 shapes and sizes, over 100 of which are non-rectangular, and they install fittings--as many as you want--in the sizes and locations specified by the customer when they make the tank.
Depending on the tank location, a single
1" vent line may be as effective at preventive odor
as two. You won't need a port for a gauge if you go with a tank level indicator that has senders which attach to the outside of the tank.
All that said, if a leaking inspection
port is the only thing wrong with your existing tank, you may not need a new one. Inspection ports
don't thread into the tank itself, a threaded cover threads into a flange that's secured to the tank using screws and sealed by a rubber gasket
. A rubber o-ring seals
the cap. I suspect that reinstalling the screws and replacing the gasket
and o-ring just might solve your problem. Worst case scenario, you make the hole larger and install a larger inspection port. Ronco also has the inspection ports
and replacement gaskets and o-rings.