Crystal clear waters

15/07/2006 by Mark.Whalley.

15 July 2006

Having put it off over and over again, I decided that it was time to tackle the water tank.

Suspecting that the tank cover had not been lifted since the boat was built, we had never actually drunk any of the water from the tank over the previous couple of years. Although the water came out visibly clear, as the tank became empty, there would always be a brown rust residue clouding the water. It this point I would refill the tank and within a couple of days after the residue had settled, it would be back to its ‘normal’ clear state for a few weeks / months. Whenever we wanted drinking water we would use 5 ltr plastic bottles which we would keep on having to refill.

 

One water tank inspection cover with barely visible securing bolts!

 

Obviously this could not continue, so with warm and dry weather forecast for the weekend and having worked from the Annex (aka home) on Friday, I decided to set off at 05:30 on Saturday morning with the intention of getting a full day on (or more precisely in) the tank, and if necessary would also have Sunday as contingency. As Bev had not been to the boat for while, she was going to follow me up (with Max) later on Saturday afternoon and stay until Monday.

The first challenge was to attempt to remove the sixteen countersunk Allen key bolts. With many years of exposure to the elements this was not going to be an easy task. No matter how clean I made the Allen key holes and how much WD40 I applied, simply using an a Allen key was clearly not going to work. The only think for it was to drill each bolt out with a tungsten drill bit. Ensuring the bit was slightly smaller than the bolt enabled me to use a pair of nose pliers to remove the shell of the screw threads. I then used a tap and die set to rework the holes to the same size of the original bolts. A couple of weeks earlier I had managed to remove a number of these bolts, and although I had considered alternatives to the replacement countersunk option, had decided to stick with the same. Screwfix (http://www.screfix.com/) supplied me with a bag of 50 bolts which would mean I had spares for whoever would be the next person to lift the cover!

 

16 new bolts (well 15 actually!)

 

With the cover removed and remaining water emptied, it was time to tackle the inside of the tank. As can be seen from the photos, the years of neglect had resulted in rust forming in several places

 

Back and port-side walls. Angled pipe in lower corner (centre) is feed to water system.

 

Bow and recessed gas locker base.

 

Several hours later with loose rust and bitumen removed, the tank is ready for painting.

 

Not much room down here!

 

With loose rust and bitumen removed, ready for cleaning and painting

 

ditto

 

Look at those white feet (and beer gut!)

 

With the walls of the tank now cleaned, I applied three coats of bitumen paint (that which is approved for potable water). Unfortunately, the fumes from the bitumen were so strong, I could only stay inside the tank for a few minutes at a time. This made the whole job much longer.

 

Nice shiny black bitumen

 

 

Having taken measurements of the inside of the tank, and taking into consideration the angled port and starboard side walls, the curvature of the bow and gas locker resses, I attempted to calculate how much water could be held in the tank.

I also did a controlled filling of the tank whereby I took the average time to fill a 5 ltr water bottle a number of times and then the time taken to fill the whole tank.

At 250 gallons (950 ltr), amazingly, I was only out by about 10 ltrs!

Over the following weeks I filled and emptied the tank 3 or 4 times before the water lost its bitumen taste. But at least now I can happily (and more importantly safely) drink the water!

One more ‘tick in the box’.

 

 

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