Removing a Centaur Water Tank
The Centaur water tank is encapsulated under the forward cabin V-berth and is not normally accessible. The tank is stainless steel and is supported between the aft bulkhead of the chain locker and the bulkhead behind the V berth aft vertical face. After 30 or so years it is not unusual for the water tank to develop pinhole leaks along the welds and possibly even a crack along the lower edge welds. This will become apparent as fresh water seepage (taste test) under the centre of the floor near the main cabin cold box. The water will appear to come from the forward direction and can be surprisingly copious.
To deal with this there are two basic options:
(1) Stop using the water tank and fit say a flexible tank into one of the side lockers.
(2) Cut through the fibre glass top of the V berth to expose the water tank and remove it for repair or replacement.
Option(1) is obvious but (2) requires more explanation.
Warning! Before you start make absolutely sure that the leak is from the tank by emptying and filling the tank repeatedly and observing the water under the bilge or by adding food dye to the tank. Also make sure that the water tank breather and inlet and outlet pipes are not leaking and that the water pipes to the sink and heads are intact.
If all other possibilities exhausted then to remove the water tank proceed as follows:
(1) Make some exploratory drillings to ascertain the location of the edges of the tank. (2) Draw lines on the V berth to detemine where to cut. (3) Using a dremel with a right angle attachment (important otherwise there is more risk of breaking cutting disks) cut inside the lines and progressively expose the top surface of the water tank. (With care this might take 3 to 4 cutting disks)
The hole will have to be a little larger than the tank especially on the starboard side to allow the tank connection to clear. (4) The tank will probably have a harness of glass fibre supporting it. Cut this and remove. (5) The tank is very tightly located between two forward and two aft vertical members. The tank also sits on forward and aft horizontal ledges. (6) Before the tank can be removed the starboard forward and aft vertical members MUST be removed. (7) The vertical members are screwed and glued to the bulkheads with three countersunk screws. Locate the aft starboard screws clean up the heads and remove them if necessary by cutting around the heads and gripping the exposed heads with long nose pliers. Then "chop" out the aft starboard vertical member using a mallet and a mortice chisel. (8) Now locate the 3 screws in the starboard and port forward vertical members (head down lower chain locker to do this). (9) Remove the screws as before and again "chop" out the two forward vertical members. This is definitely a hacking job but try not to damage the bulkheads too much.The vertical supports will probably be destroyed and will have to be replaced. (10) It should now be possible to move the tank up slightly and forward so that it sits on the top of the forward horizontal support. From this position it can (honestly) be manoeuvred out.
(11) To assist removal shorten the breather spigot and the inlet filler pipe. (12) Having removed the tank locate leaks using soapy water and air pressure from a vaccuum cleaner on blow. Then either repair it by welding, replace it with a flexible tank or with a new rigid tank. (13)Repair any damage to the bulkheads using epoxy and tape. Replace the front horizontal support if it is decayed and possibly construct a shelf for the tank to sit on so that in future the stresses are not only along the edge welds. The shelf can be slung underneath the horizontal support and built up to the correct height. When repacing the screws in the vertical supports use stainless screws and large penny washers to spread the load. To allow the tank to be removed more easily in future do not reglue the vertical supports. The picture below shows the new supports and underslung shelf (more about this later) in place. The starboard vertical support is standing unfixed in its approximate position.
(14) Finally manufacture a new hatch cover to cover the hole in the V berth. Screw this down onto battens added under each side and onto the forward and aft bulkheads.
Timescale for the Job
If all goes well and the vertical supports are removed as decribed the tank can be removed in one long day. Timescales are then determined by how long it takes to get the tank repaired or replaced (say one week) and how long new parts take to manufacture and fit. Overall say 3 weeks. However without removing the vertical supports the tank is so firmly fixed people have been known to spend weeks just at the first stage!
Keeping the Wet Stuff Out. Brian Stevenson Pg 89 Westerly Owners Association Magazine Winter 2011 Available here in WOA Members Technical Section