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Installing a pump out toilet

How easy/practical would it be to replace a cassette toilet with a pump out one on a narrowboat?

Asked by: Paul Taylor  | 3.52pm, Thursday 28 June

WW says:

Generally, the answer is "reasonably easy".
However, there are a few things to consider.
1 Where will the tank go (the bigger the better!) but if mounted off-centre, consider the difference in trim between empty and full!
2 Have you easy access to fit a deck mounted pump out and rinse out fitting? Plus you will need a vent (preferably 1 1/2" diameter) in the hull side, usually. if you can mount thepump out/rinse out on the gunnel, rather than the cabin roof, it is easier to empty the tank well.
3 Make sure that you can easily seal off (neatly) the bulkhead where the cassette toilet tank was removed (if it wasn't taken out through the toilet compartment itself).
4 If you will be using a macerator or vacuum flush toilet, if your battery capacity sufficient to provide for it? if not, you might need to upgrade your system slightly- although they only work for short periods, they do take quite a high current draw when the unit is running. If wiring, or battery/charging capacity is insufficient, voltage drop can cause some units to stop working!
Make sure that the floor area below where you will fit the tank is sufficiently strong to withstand not just the weight of the tank, but able to secure the tank, so that it cannot come loose if the boat strikes an object, or tilts over if the boat catches in a lock, for instance. The idea of 400kg+ of sewage tank (and contents) coming adrift and splitting isn't worth risking!
If you need more specific advice, then please do ask. It is quite feasible to do this- just plan ahead, though I should point out most times people convert from a pump out to a cassette/Porta Potti, rather than the other way round.
Best of luck!

Mark Langley  | 8.08PM, Thursday 28 June

As Mark's answer shows, it is possible to install a pump-out toilet in place of a cassette type, although it does entail some upheaval. Then there is the cost of having the tank emptied which is around £15, plus the thought that you might find yourself unable to get to a pump-out station if you are iced in or there is a stoppage.
For these reasons, many liveaboard boaters opt for a cassette toilet from the start and would never change. Modern units have ceramic bowls which are easier to keep clean and look very similar to domestic units. You can also buy an extra cassette or two to extend your range.
Before you go too far with your conversion, it might be worth thinking seriously about upgrading your existing arrangement and saving yourself a lot of effort.

Graham Booth  | 6.15PM, Friday 29 June

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