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Poo tank

We have been experiencing difficulty in emptying our poo tank for some time now, whilst we have found a boat yard that will pump out via the toilet itself this is less than ideal. The pump out stops after a short time and the vacuum air pressure is considerable suggesting that something may be blocking the outlet. I have tried a household drain unblocker - a tick wire some 2m long which gets into the tank without effect. The boat, and I assume the pipe, is 22 years old the last pump out operative suggested that the pipe may be de-laminating internally resulting in a blockage once the suction of the pump out takes hold. The suggestion being a replacement pump out pipe. A horrible job yes but attention is needed!!
Any thoughts?

Asked by: Chris Marriott  | 9.00pm, Sunday 14 September

WW says:

Alas the old saying "no matter what toilet system you have, at some point you will need to get up close and personal- with a pair of rubber gloves" has happened!
It does sound like the suction pipe might have collapsed internally- they don't last forever. While is is certainly not the most pleasant of jobs, you can add some warm soapy water down the pipe before you try and remove it. However, they can be stubborn to remove from the fittings, and you might find a hot air gun (or hair dryer) useful to soften the pipe if it refuses to budge.
If you use a suction pipe designed for toilet systems, it will be more impervious to any smells leaking through, and should be more resilient than some of the older types fitted. Try and use stainless steel jubilee clips as well when reattaching the new pipe work.
When you remove the old pipe, you might be able to give the suction pick up a good ridding through- one of the other issues that can happen is that line scale buildup can drastically reduce the internal diameter of the pipe work so increasing the draw down pressure when trying to empty the tank. Often the choice of holding tank treatment determines how much lines cake builds up- but scale also attracts other debris...noticeably toilet tissue or, if anything that has not broken down, such as wet wipes, has ever entered the system. Many older holding tanks are not great design, making it almost impossible to empty them completely, and they do tend to sludge over time, which can exacerbate things somewhat.
If you do replace the pipe, it is worth checking that the pick up pipe has also not deteriorated- as that might need replacement as well. This could be an easy job or one fraught with difficulties, depending on how it is physically attached to the tank.
It is also worth checking the status of the tank vent pipe, if fitted, though as it sounds like you have a dump-through toilet, air should be able to enter the tank when it is being emptied- and reduce strain on the tank itself.
Best of luck though- toilet systems on boats are never perfect, but hopefully it will be a fairly straightforward job- just try and avoid breathing in any aerosols that are generated when you remove pipe work...

Mark Langley  | 10.51PM, Sunday 14 September

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