Glassfibre Freshwater Tank

[Lofty]

I want to build a glassfibre freshwater tank; two of the sides and the bottom will be formed against the glassfibre hull and the other two against marine ply bulkheads. I am told the lid is best made from plastic sheet and I have a friend who will supply this. Can anyone tell me, what are the best materials to use to ensure that my drinking water is not tainted? Is there a particular kind of gel coat I should use on the inside? Any tips would be appreciated.

 

[oldsaltoz]

G'day Lofty,
And welcome to the YBW forum.

A fibreglass tank will last years, not sure why you are fitting a plastic top thou?

Anyway, make sure the epoxy you select is an epoxy resin, this will provide a much stronger bond and stand up to water.

You will have to remove any coating that will be exposed to the water as it may contain unsafe material or not suitable for continuous submersion.

When you are ready to start glassing, fill in all the corners with a mix of resin and 'Q' cells, or you can use talcum powder if weight is not a problem. the back of a soup spoon will give you a good a profile and make it easy to clean later.

Also ensure the fibreglass you use to glass the ends in is suitable for epoxy resin, (No chopped strand), you should be looking for a close weave that will provide a volume of 2 parts cloth to one part resin, this will give maximum strength and minimise weight.

When all the glass is in place, give the whole inside three coats of resin with a light sanding between coats if it goes past the tacky stage.

I hope this helps

Avagoodweekend.................Old Salt Oz /forums/images/icons/cool.gif

 

[PaulJ]

I would agree with Oldsalt and add the following... Fresh water causes worse osmosis than salt water so it is vital that you use epoxy and not polyester resin. Some years ago I had a Hurley 24/70 which had a self contained glassfibre freshwater tank. When I took the top off to clean the tank I found the finest display of osmotic blisters you could ever wish to see! I cut the tank out and replaced it with a flexible tank. You might even like to consider using a flexible tank instead.....?

 

[castaway]

Lofty

I also would tend to shy away from GRP fresh water tanks. Not only from the osmosis point of view buy also I remember when these tanks were quite popular, lots of people were reporting "mystery" sickness whilst sailing, which was after a while thought to be due to the styrene leaching from the GRP into the drinking water.

Flexable tanks are so much easier, healthier and not expensive, I would look at these.

Regds Nick

<A target="_blank" HREF=http://www.yachtsite.co.uk/fairweather>http://www.yachtsite.co.uk/fairweather</A>

 

[ccscott49]

I have fibreglass tanks on my boat, independant ones, I don't know if they are epoxy or polyester, but I still get a nasty taste from them after 30 years, by all means build the boxes to carry a tank, but put a flexible liner tank in there. IMHO. When I get a leak from mine, they're history! Mind you they are still fine and I filter my drinking water, I will be trying Chempro this year!

 

[Chris_Robb]

I have built in glassfibre tanks (built 1977). No sign of any tainting in the water and no sign of osmosis in the tanks.

 

[dickh]

Have you thought about fitting ready made plastic tanks?
Have a look at www.tek-tanks.com who supply a variety of sizes as well as gauges etc. Probably more expensive but a good deal quicker and much less messy!


dickh
I'd rather be sailing...

 

[gunnarsilins]

Agree with Chris on GRP-tanks

I have two on my Moody built -77.
I have no idea about blisters, from the looks of the man-holes nobody´s been in them since the boat was built.
But the water tastes and looks perfect.

 

[gtmoore]

Re: Agree with Chris on GRP-tanks

Might be worth a look. One of my '81 Moody GRP tanks had a leak so I opened up the lid to see what was happening (actually more like had to cut it off!) and it was not a pleasant sight.

Water tasted perfect but you wouldn't drink it if you saw the insides - blisters and black bits and ...yuck. Ripped open the other one (looked the same!), cleaned them all out and popped in a couple of Plastimo liners instead.

 

[gunnarsilins]

I´m not sure...

...if I really want to see what´s inside after 25 years!

But I beleive that as long the water looks and tastes good it´s safe to drink and there is no point in disturbing whatever creatures and nastities there might lurking inside.
But if something changes, or a leak appears it would be a different matter.
Or am I wrong....?

By they way, have you ever been looking inside old domestic water pipes? It´s not a rewarding sight either!

 

[ccscott49]

Re: I´m not sure...

As long as the contents of the tank doesn't slop about as with a house, then the creatures of the dark lagoon will probably stay where they are, but my tanks get a vigorous shaking each time I go to sea, which disturbs the monsters, I have a filter for drinking water, so if the water looks a little brown, I don't care. But I will be treating my tanks and pipes this year, to a thorough clean with Chempro and treble flush out, as reccomended in these pages!! The water has got a little thick of late!!

 

[claymore]

Vetus too

I once fitted one and it worked fine- they come in a range of size and shapes

regards
Claymore

 

[gtmoore]

Re: I´m not sure...

Hmmm - problem is if the lids to your tanks are like mine they just won't come off and be reuseable afterwards so you end up with a problem. I had to drill big holes with a hole cutter so I could lever them off and they broke in the process. They were screwed and mastic'ed on so obviously not set up for cleaning regularly!

I take your point though that if it tastes ok it probably is.

Cheers

Gavin

 

[gunnarsilins]

On my boat....

....the cleaning is easier. There is a large (appr. 30 cm square) aluminium cover bolted with numerous bolts and a cork gasket behind.
The same on the GRP diesel tanks. On these the lids came off easely two years ago, when I cleaned them, probably for the first time ever.

But even if I think that gaining access to the tanks is fairly easy, I think I leave the zoo alone for the time beeing!

 

[Lofty]

Thanks everyone for all the helpful information. I have added a soup spoon to my toolkit already. (Thanks Oldsaltoz) Tek-Tanks made a fuel tank for me some years ago and very good it was too. This time expense has to be a major consideration and anyway I don’t think I could describe the shape of the compartment I want to fit the tank in.
The plastic lid idea simplifies the construction as I only have to position some battens around the top and then glass over them. The plastic lid will then be screwed down on a bed of silicone sealant and job done. An inspection hatch will be put in it first. This construction method has worked well on a friends holding tank.
The tainted water problem has worried me but I am now told that I need a Gel coat, which has an element of wax. I know of two other boats with Glassfibre water tanks and they have no problems, so I shall go for it.
Since both my flexible tanks leaked and flooded the bilges I have been using a plastic container. I soon had a problem with tainted water. I tasted the water in the container and found it was perfectly alright. However, when it arrived at the sink via the footpump and about 8 feet of plastic pipe it was foul. I suspect this may be true in other cases.

Thanks again everyone

 

[ccscott49]

When putting the lid on with sealant, put the sealant one the tank face, then put some clingfilm on top of the sealant, put the lid on and tighten down, you will get a good seal, but you will also be able to get the lid off at a later date to inspect the tank, unless you are fitting an inspection hatch in the lid, in that case, don't use silicone, use polyurethane and bond the lid down! use the clking film trick on your inspection hatch and use polurethane, silicone sealant has no place on a boat.

 

[gtmoore]

Regarding your pipes - were they clear or opaque? I repiped my boat with clear by mistake and had to rip it all out after a few months cos the pong from the first few pumps of the taps was knockout. The new blue pipe seems fine so far.

Gavin

 

[Lofty]

You are dead right. The pipes were clear. They went in the bin some weeks ago. But I can't help wondering how many have this problem and blame it on their tanks.

 

[ponapay]

I have built in glass fibre tanks, built 1970 and full of osmosis.

I have had no taint in the water. Three years ago I painted them inside with difficulty and now have large paint flakes coming off.

A friend with similar boat removed all the saloon furniture, the sole and tank top. He then ground off the gel coat, allowed it all to dry and recoated wiht epoxy. As far as I know it all worked well.

Use plastic, save up for a Tek-Tanks tank, they work well and though mine has been in use only for 4 years has caused no problem.

 

[Maurice55]

If you still want to build your tanks after all this, maybe you could have a look at products like Sika-gard (from Marine and industrial sealants )which is certified for drinking water. (it's a two part epoxy paint)