A1Sailor
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As a matter of interest, I've not had to drain our water trap/sediment bowl in the 10 years I've had this boat but haven't a clue what's lurking just below the level of the pick-up pipe. As I can't get to my tank inspection cover without cutting a hole in the galley worktop, I've bought one of the electric drill pumps and will see if I can drop a pipe down through the hole drilled for the Eberspacher stand pipe.
Why not just drop the end of a PELA suction catheter into the bottom of the tank via the filler pipe, assuming of course the tank isn't so remote that the pipe has a tortuous route? It's a relatively easy way to at least sample whatever may be lurking at the bottom, and remove water.
http://www.seamarknunn.com/acatalog...gclid=CIaX_6iN2LsCFTDMtAodTyEAxQ#.UsF77LTAiRM