Holding Tanks

The holding tank imploded in my boat. T-valve in locker behind toilet must have been in position so that there was no air suction through toilet and the air outlet/inlet hose through hull was totally choked. So when discharging with regular membran pump, the whole tank imploded. Quite a job to get it out of forepeak for repairs since tank quite much out of shape. It was funny cause there were no special sounds like cracking or anything indicating such things going on.

Also drained fuel tanks just recently since there was no flow from the one tank to the other, so now have to blow all lines with air pressure. There was quite an amount of water and sediments in tanks. Having had the boat for 8 seasons, it was the first time I did this. It wouldn`t be difficult to imagine what kind of problems that could occur when at sea or anyplace since water seperator system probably takes only half litre before water continues to engine. It`s a bit frustrating to close man-holes again without having had access to entire tank for cleaning sediments, due to bulkheads. Assume this very difficult to do without taking out tank. The biggest tank on starboard side in saloon is so much built in that there is no way to get it out for flushing. Would be t(h)ankful to any good advise in this respect. Thorbjorn/Ravn 411/036

Ravin, on my 411 the fuel tanks are all one but at two levels. When the fuel gets low enough to a level that you can open the inspection hatch on the bottom tank I have put a siphon into the bottom and taken out water and solids. Let the siphon run into a bucket until you get clean fuel.

John 411 /10

Ravn,

You must have a good sense of humour to see a funny side of your hoding tanks imploding!!

Interesting comment about the vent being blocked.  We are just fitting two new holding tanks.  The smallest vent size that the manufacturer (Tek tank) would fit was 25mm.  I thought this a bit large, but after your story maybe not.

Cheers

Adrian

Blocked air vents:

I had the problem with the grey water tank on our 41. I believe the reason was a bees' nest in the outlets situated under the transom... Some bees in the south of France (and Italy I suppose!) lay their eggs in small mud made bottles which are apparently very efficient to block the vents. So dont forget to clean the vents with a wire regularly!

Yes indeed,
I had small bugs (probably the same mentioned) plugging the vents and giving me headaches regarding the gray water tank, the holding tank and even the anti-siphon copper hose of the raw cooling water system of the engine.
In particular the last made the engine flood: a scary experience!
Now I carefully check all the vents at least once a year.

Daniel, 411-004