Water tank capacity - Experience and sensible size

[davey b]

I started a job I've been putting off for ages today - cleaning out the water tank. I lifted the access plate expecting the worst (I've not been in there in 3 years of ownership...) but was surprised to find a good solid coat of blacking and nothing really of note. This is, of course, after ordering £70 worth of Vactan to do the job! So a measure of Milton will do for now.

 

As I expected, the tank goes almost all the way to the nose and is full width and half height giving a capacity of (very) approximately 400 gallons. I was very surprised to find it about half full still. I haven't filled up since May and clearly not using it much, it has lasted too well. I will be moving aboard at some point so the point of this ramble is this: Is 400 gals a sensible size tank or can I realistically recover some storage space. My idea was a new bulkhead and a flexible liner tank of about 200 gals.

 

Incidentally, that amount of water weighs nearly 2 tons so has a significant effect on ballast and handling as it is right at the nose. It has no baffles either so the slosh effect may be reduceable too

[Mike Tee]

200 gallons is ample if you are able to fill up every couple of weeks (excluding using a washing machine daily). 400 gallons would be even better.

However, come the big freeze, you would be better having a flexible liner kept insulated from the hull sides, rather than a tank separated from ice by 6mm of steel. The last thing you want is a large iceberg in the front of your boat, and nothing to do the washing up with. Different handling and no slosh will only be a benefit if its a problem now.

[blackrose]

However, come the big freeze, you would be better having a flexible liner kept insulated from the hull sides, rather than a tank separated from ice by 6mm of steel. The last thing you want is a large iceberg in the front of your boat, and nothing to do the washing up with. Different handling and no slosh will only be a benefit if its a problem now.

 

I completely disagree.

 

In 13 years of living on boats with integral tanks I've never once had water freezing in there - at least not to my knowledge or to the point where it caused any problem. Conversely a friend of mine with a stainless steel tank on a boat built by the same boat builder had frozen filler and breather pipes which resulted in him pulling a vacuum in the tank when he used the taps. Suddenly there was a big bang, but fortunately no damage.

 

He'd filled the tank during the day and because the filler and breather pipes have to span the gap between the top of the tank and the deck they froze during the night. The space between the tank and deck was insulated with rockwool, but it didn't help.

 

That situation is almost impossible with an integral tank because the filler only comes up to the deck height. Even if the top of the water in an integral tank did freeze - which is highly unlikely - it wouldn't block the outlet because it's at the bottom of the tank and I can't see it causing a vacuum because it would be a thin sheet of ice over a wide area, so easily broken.

 

I'm prepared to be corrected, but I'd be surprised if there's anyone on this forum with an integral tank who's ever had a problem with it freezing.

 

Edit: By the way, my tank is 1275 litres (280 gallons) - on a widebeam.

Edited October 17, 2014 by blackrose

[DHutch]

Unless you have a major storage issue I would be temped to leave it, our tank is more like 80gallons which works as we move all the time but doesnt last long at all once you stop. Often only a day or two if there more than one of you wanting a shower.

 

You could always add a baffle if thats an issue.

 

Vactan appears to be good stuff, used it for the first time year on a vintage digger and then on the boat, but £70 worth is a hell of a lot. 5l I assume?

 

 

 

Daniel

[davey b]

Yes, Dan; 5 litres - there is always the car in its 21st year!

 

Blackrose, surely that would depend on the design of the filler and vent rather than the design of tank. I appreciate the volume being difficult to freeze completely is used to good effect in all these tanks but my suggestion of the flexible liner was more aimed at the lower maintenance of the interior than thermal separation.

 

Changing the shape and size may fall into the 'far too difficult' tray

[Sabcat]

300 gallons on ours. Wouldn't want it any smaller. The more water you've got the better, it's useful stuff. Unless this big tank of yours is causing a problem leave it be.

[DHutch]

Yes, Dan; 5 litres - there is always the car in its 21st year!

 

A whipper snapper!

 

But yes, some when on the 19yo BM and some may yet go on the 24yo kitcar. I bought half a litre to try and have just bought my second half litre this week.

 

 

Daniel

[blackrose]

Blackrose, surely that would depend on the design of the filler and vent rather than the design of tank.

 

 

So how you would you connect a filler and a vent from a stainless tank to a deck without adding pipes to the tank? If temperatures are going to go sub-zero, the main thing to bear in mind is to use a bit of water from a stainless tank after filling in order to empty the pipes.

[davey b]

Understood; my point was rather more towards that being a problem (or not) on most designs. My integral design has a filler pipe and vent pipe too. The tank on mine is only 24 inches deep up from the base plate and the filler is on the deck.

 

I'm not convinced it would make a difference whether I have a liner or not.