With all the beautiful harbours that we have been visiting it's not surprising that our holding tank has been getting pretty full. Whilst every opportunity has been taken to use the marina facilities in some cases this just hasn't been possible.

With our decision to leave the Golfe du Morbihan, we had an opportunity to empty our holding tank whilst well out to sea ... but there's a problem!

The pump that empties the holding tank is heard to be working but the tank remains full! Why?

Option 1 - Could it be that the pump seal is incorrectly fitted or damaged and not creating a vacuum?
Option 2 - Could air be entering the system through one of the many joints above the pump?
Option 3 - Is there a blockage somewhere?

Whatever the problem, none of the above would be very pleasant to deal with! Rubber gloves, plastic sheeting, wellie boots, a nose peg and lots of boiling hot water with plenty of soap spring to mind. I really wasn't looking forward to it.

Thank god for the internet! Other cruisers have experienced the same or similar problems and some ingenious ideas have been put forward to remedy the problem.

Given that the holding tank was only fitted recently specially for our adventure, we can't say that it has been thoroughly tested apart from being filled a couple of times with sea water and emptied successfully. This sort of suggested that the pump and seal were ok and all the joints sound and airtight which left us with ... a blockage somewhere!

So as for those ingenious ideas, they were mainly based on feeding a piece of stiff wire from the holding tank outlet back up through the system to the pump or doing the same with pressurized water or air. Well, you need to know that our outlet is a good half meter below the waterline - so you really need to be in the water to do this. This might be fine in the Med, where the water is warm but not so pleasant here in South Brittany at the moment. Even so I'm not sure that I would want to be underneath the outlet when the blockage is cleared.

Whilst I was not keen on the idea of using wire or indeed water pressure, the concept of using air pressure appealed. If I could somehow connect the dinghy pump to the outlet, I could possibly force air back through the system and hopefully clear it assuming it was a blockage.

All this sounds well and good but would really have to be done in the safety of a Marina or Harbour ... precisely where you shouldn't empty your holding tank!

Then a potential solution came to me ...

By blocking the outlet (turning off the seacock) and flushing the toilet with seawater, water would fill the outlet pipe and make its way back up the pipe, passing the 'Y' connection and then along the holding tank outlet pipe to the pump and then onto the tank itself. Hey presto, a couple of minutes later the blockage had been cleared, the pump started and the tank drained and I emerged from the heads with a smile on my face and more importantly clean hands and not smelling of S***.

All I can say is thank you "Google" for kick starting the idea.

Following further research it transpires that some cruisers use chemicals to breakdown their waste and talking with Dom and John from HT Tapestry they had read on another forum that washing tables can be used to do this. Subsequently they had us in real hysterics when they came over with a couple of tablets and at the same time (with a straight face) said "by the way they don't include softener!".