Hi there. Its my first post so please forgive me if I am doing something wrong!
I am looking to install a 23 gallon polyethylene holding tank
under the side deck
of my sailing boat in the next 6 weeks and would value thoughts, comments and any helpful suggestions on my plan and help with some questions.
The bottom of the tank will be about 600mm (2ft) above the waterline and I propose to have the drain outlet at the bottom of the tank and gravity discharge it through a 50mm (2”) TRU Design ball valve attached to the bottom of the tank, then through 500mm of sanitation hose to a 50mm (2”) TRU Design ball valve and skin fitting.
The heads discharge pipe will go straight to the top of the holding tank
without an anti-syphon loop, my logic is that the holding tank vent is in effect the anti-syphon.
The tank will vent from the top of the tank to the side hull
using 38mm (1.5”) pipe taking a horizontal path and a length of approx. 500mm (2ft).
O and not to forget the pump out from the top of the tank directly above the discharge at the bottom of the tank. I got that gem from Peggie Hall’s book.
1 – Should I have one 38mm or two 25mm vents (the top of my tank measures 530mm fore and aft by 240mm?
2- What should I use for the outlet at the bottom of the tank? I am thinking of using a skin fitting which I can fix the ball valve to.
3 - What should I use for the outlets at the Top of the tank? Again I am thinking of using skin fittings although it has been suggested by the company I am going to buy the tank from that I use ‘Uniseals’ instead. Does anyone have experiance of these?