Yacht ‘Enterprise’ Van Dam 34
Built at Van Dam at Aalsmeer, Netherlands 1974
MMSI 244130118 ; Call Sign PH 5626
There is a custom made (2005) polyethylene grey/black water tank (110 litres) located under the main cabin floor. This tank takes water from the galley & heads basins and the toilet (if the diverter valve is set to this position). In fact the diverter valve is rarely set to this position as black water is usually discharged directly to the sea (except in the Baltic) and when in a marina, shore facilities are used. The tank can either be emptied by way of a vacuum pump through a deck fitting or directly to the sea by way of a bilge pump located on the forward bulkhead of the sail Locker and operated by a handle in the cockpit. This bilge pump was replaced in 2008 with a similar one, but more modern design, as it was found that if a seal failed it could siphon back sea water. Just to be on the safe side , a back-flow preventer was installed at the same time. The tank is vented to the exterior through a fitting on the coach roof.
Grey / Black Water Tank Plumbing
Grey / Black Water Tank Diverter Valve
Johnson Pump Toilet 2015
The toilet, new in 2015, is a hand pump with double action, both evacuating and flushing the bowl with seawater (Jabsco 29120-2000). This model is designed to accept an electric pump but we have not gone for this added complication. There is an anti-siphon valve in the flush line between the pump and bowl.
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Grey / Black Water Tank Ventilation
 Grey / Black Water Tank Plumbing
The direct sea discharge from the toilet is routed above water level, through an anti-siphon valve located in the hanging locker. The vent pipe and vac pump-out line are also located there. 
Original Bilge Pump Replaced in 2008 With Same Capacity
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There is a high volume, manual bilge pump in the engine bilge for emergency use. We have only used it once, when we first bought the boat and the stern gland failed. With proper maintenance it should never be needed but it is nice to know that it is there and in good working order. There is never more than a small quantity of water in the engine bilge and we generally mop it out. Keeping the grease pressure up in the prop shaft is the key to a dry engine bilge, as long as you don’t leave the sail locker and lazarette open in a thunderstorm!
Engine Bilge Pump
This pump can also serve to pump the amidships bilge (under the battery) but we have never used this feature as it is always dry.
Mid Bilge Plumbing
We had to stay on the boat when it was in a cradle in a boatyard with no facilities so we purchased a chemical toilet (Thetford Porta Potti) which is stored in the Bow Locker. This is also useful when there are no shore facilities and no Vacuum Pump-out available.