Jim asked... My problem is this - I suspect that POs were not that aggressive about pumping out and that there is still tightly packed 'stuff' in the bottom that has yet to loosen and evacuate (boat is 25 years old). I think I need a high pressure waterjet to break it up, but I currently have no way to do it. I am reluctant to cut a new hole unless there is a high probability of success. Dennis suggests... We went through this several years ago with a similarly aged boat. The problem develops with a system which is mostly emptied in pump out situations. As the tank is pumped out by suction, when the vacuum is broken, removal stops, leaving the heavier than water stuff in the tank. Over time, this more or less solidifies, and becomes a sticky insoluble mass. We are able to access the top 6 inch port of our tank, and could use a stirring stick and high pressure from a hose to loosen then pump out the broken up semi-solids via a macerator pump which is mounted below the holding tank. After the initial cleaning of the near-solids from the tank bottom we now, after pumping the tank either at a pumpout station or via the macerator pump, rinse the tank bottom with high pressure form a hose, and repump the tank a few times. Annually, prior to winterizing, we pump and rinse several times to eliminate any buildup. After all this, on occasion a buildup can occur in the macerator pump, blowing a fuse. We solved this by a plumbing solution which allows a valve isolation of the macerator pump, and a port to allow clean water to be rinsed through the macerator after a pumping the tank overboard. Details for this are on my website (see below link). See "Boating Articles" on the right margin. This was published in DIY Boating several years ago. If interested and can't find it, I can send to anyone wanting it as an attachment in Word. Dennis Dennis Bruckel, Cruising Editor Waterway Guide Albin 27 Sadie B website www.debruckel.com cell phone 407 414 0531 e-address: dbruckel@earthlink.net