New skin fitting

[macd]

Baba Yoga: it was my assumption that the OP wants to be able to discharge the pump directly into the sea, but to retain the use of the holding tank occasionally, as needed. This certainly seems his simplest option as it can be achieved by a single diverter valve downstream of the loo, plus skin fitting/valve. It would no doubt be helpful if clonlara can confirm this.

The reason for my questions about the height of the holding tank relative to sea level, of course, was to determine whether a straight-through holding tank , as described by Vyv, might be possible, since this would be the simplest of all solutions. Unfortunately it isn't.

 

[BabaYaga]

Baba Yoga: it was my assumption that the OP wants to be able to discharge the pump directly into the sea, but to retain the use of the holding tank occasionally, as needed. This certainly seems his simplest option as it can be achieved by a single diverter valve downstream of the loo, plus skin fitting/valve. It would no doubt be helpful if clonlara can confirm this.

I might have misunderstood the OP's intensions. If he is happy with only ever being able to empty the holding tank by discharge station, then a diverter valve + seacock between toilet and tank make sense.

 

[prv]

I may have misunderstood what he said - 'discharges high up in the tank'.

As in, it empties into the top of the tank. The tank is still low down in the boat - under a bunk, isn't it?

Pete