June 23, 2002 – MV Tortuga

From day one I’ve known that the steel holding tank on the port side had to be replaced.  Many months ago I started replacement of the sanitation systems by removing the old “black water” sewage line running the length of Tortuga.  As much as I hate admitting it, right now Tortuga couldn’t pass inspection since the toilets all pump overboard.  So prior to getting underway again we must rebuild or replace the entire system.  The next logical place to work was tearing out the old tank and the rain all this weekend gave me no more excuses.  I knew this job would be awful since the tank is too large to be removed through either the forward or aft engine room hatches.  The first tasks was to cut all lines (vent, pump out and inlet).  It was during this process that I discovered the most interesting thing.  On the outboard lower corner of the tank was a valve and fitting which led to   —  MY FUEL SYSTEM!  Being the bright engineer that I am, I thought – wow, an ingenious way to incinerate waste onboard.  Reality caught up in minutes and lots of things started making sense.  I’ve always wondered why a black water tank would have a site tube.  Now it was clear, this 170 imperial gallon tank was once the genset fuel tank.

Removal of the tank was going to be done in stages.  First, cut the top off around 10 inches down.  This would give me sufficient height to lift the tank with hydraulic jacks over the rails in which it sat.  Then, swing the tanks aft end amidships.  Then cut her in half again for removal.  Steps one and two went well.  After six hours of cutting, jacking, wedging, and pulling, the aft end of the tank was in the middle of the engine room floor.  But the fun came to a screeching halt once I started to cut the top off.  After making all cuts, the top wouldn’t budge.  It turns out that the suction end of the pipe was frozen in a 3″ well at the bottom of the tank.  The only option was to cut a hole in the side near the pipe and reach in with my SawsAll and cut the pipe internal to the tank.  But the fun was just now beginning.  After cutting the hole I found that there was 30 gallons of solid and liquid waste still in the tank.

Holding Tank Photo

Finally the top was off and carried to the dumpster.  A trip to Publix provided 50 lbs. of cat litter which was “thoroughly” mixed with our “black mud.”  This concoction was allowed to stand for a day to solidify.  The next task was shoveling this mass into garbage bags for removal.  I kept sitting on the stern in my comfortable chair saying to myself that it would soon be over.  That is, as soon as I would get my self going.  And sure enough, a few hours later I had a reasonably clean tank (much lighter) that could now be cut in half.  The picture to the left shows the tank still in place.  You’re looking aft along the port side with the aft engine room bulkhead and door visible.


Holding tank turned

The tank being turned CCW onto the center walkway.  The top 10″ had been cut but wouldn’t come off due to the stand pipe.

Full Holding Tank

The tank with its top off and setting in the walkway.  It was still nearly full at this time!  You can see the well extending from the bottom left of the tank.

Holding Tank Replacement Complete

The picture above is my reward for 25 hours of hard work.  A perfectly clean and spacious area to mount the new plastic tank next month.  I’m ordering a 50 gallon 3/8″-wall unit from SeaLand.  I’ll update this story as works continues.

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