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Holding Tank for R32

Gravity emptying ideas.
Posted: 10 May 2021 - By: Simon Harrison

Paul Taylor asked about holding tanks on Facebook and here is the post and the drawings:

The set-up on Folie Douce was fitted in 2013 and seems to work well. It comprises a stardard 10 gallon rigid Vetus holding tank suspended in a cradle on the main bulkhead in the locker outboard of the Lavac toilet. Above the tank is a deck pump-out fitting. In line with this at the bottom of the tank is a 2" pvc ball valve, a 1.5" T connector, and a 1.5" Blakes sea cock. The Henderson MkV pumps to the top of the tank. Normal emptying is by gravity into the sea. The tank may be rodded from deck to the sea, straight through everything, borrow someone's boat hook for this. There is also a 1.5" breather through the side of the hull and the T connector allows the tank to be emptied into a jerrycan by gravity if in harbour for too long and the tank becomes full. The T also allows the shower water to be pumped up into the tank or directed directly into the sea, depending on the settings of the pvc ball valve and sea cock. The drawings show that to get all that in line, fine positioning of everything is critical. The cradle for the tank and the T (or more accurately, straight Y) fitting were both made from fibreglass as I could not buy suitable parts. A 2" ball valve was fitted but a 1.5" one might have been easier to squeeze in and it was pvc so as not to leave corrosive urine in touch with the bronze seacock. (One refinement, not fitted so far, would be to connect the heads wash basin drain to the 3/4" Blakes seawater inlet for the toilet flushing. This would allow, with the seacock closed, freshwater to be drawn from the basin into the flush pipe before leaving the boat to avoid the normal smell.)


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