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      I have noticed the odd post about blocked black water holding tanks some members have been experiencing. I have had several suggestion recently how to unblock my tank including using the arm length veterinary rubber gloves, say no more. Excuse me if this suggestion has been posted elsewhere and is now ‘old hat’.

      Whilst at my boat (B30) yesterday the Marina Manager at Portavadie (Robert Kitchin) suggested the following:
      1) Select tank sea-cock to open
      2) Wrap approx three turns of insulating tape around the end of the dinghy foot pump and jam it in the deck pumping access pipe.
      3) Have someone cover the small tank vent (located on the hull) with a rag.
      4) Pump the dinghy foot pump a few times to pressurise the holding tank and wait a moment or two.
      5) Watch with great delight as the full contents empty in (excuse me) one large cloud into the sea.
      Job done, pardon the pun.


        im soooo glad i read your blog, i had the same problem last Thursday, and tried your method, wayhay, instant success . many thanks Nornie Lees, also a bav 30


          Just a warning to you if you use this method and the tank does not unblock the temptation may be to keep pumping. If you do this and it does not unblock the tank you have effectively pressurised the holding tank. When you pull the dinghy pump hose out this pressure will release with the contents of the tank erupting like a geyser out of the pump outlet. Not nice and I speak from experience!
          In the end I used the arm through the tank inspection panel and a stick to disturb the blockage.
          On reflection it may be better to use the dinghy pump on suction which should suck sea water up through the sea cock into the holding tank, this may disturb the blockage from the “other side” and also avoid pressurising the tank with the resultant “fallout”.


            I experienced a blocked holding tank and tried all methods. Eventually I took to the tender and pumped from the hull outlet. However you need to be quick to get out of the way of the resulting eruption.

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