Building Fiberglass Fresh Water Tanks

[Alan Wheeler]

I have been out on the briney. But if I may just confirm, properly mixed ratio, properly mixed mix, properly cured Epoxy is inert an non-toxic. Infact, less toxic than roto-mould polyethelyne or just about any product you could coat on. I would leave it plain, don't coat it with anything else.
Once the intitial cure has taken place, put a lamp inside the box so as the temp can be raised. 50C is ultimate. Leave it for 24 to 48 hrs to fully cure. This will pretty much set any chains that have not come together in the initial cure stage.

[SkiprJohn]

Aloha Kai,
I build my tanks upside down and then when that is all finished I put them in place and finish the bottom last which is either part of the hull or cabin sole last. That way I have gravity on my side and can work through the clean out ports to attach the bottom to the sides and ends and put a nice clean filit and a couple layers of cloth or tape over the joints.
Just a different way of doing it if you have a large tank and can't finish the whole thing and you use part of the hull or sole as the bottom.
I use all epoxy.
Kind Regards,
JohnL

[Stevens 47]

I have been using glass bubbles as thickener when I want more strength I will mix in some chopped glass. The glass bubbles are a good filler. I only use silica as a additive to create glue not a fan of it as a filler or fillet joint agent. I also do not like the idea of ply as a baffle even if coated with epoxy. What I am doing making my own baffle panels, by covering a flat surface with 6 micron plastic laying up 3 or 4 layers of biax after gel it just peels write of the flat surface. You can cast in some angles to create an I beam. Then cut the finish panel and glue and laminate in place, very strong product. I am not a fan of woven or matt products, especially after seeing how they have failed on my boat do to the grounding it suffered in Katrina. I now only use stitched cloth or multi directional rovings. Admittedly the tanks will not have high stress loads in tanks in normal situations. I am just biased against matt and woven cloth.

Jack

[mike d.]

KAI NUI i don't what kindof resin it is i do know when i was researching B. Roberts boat building manual back in the early 80s there was referance made to make or coat the inside of the h2o tanks with a particular resin that does not leach into the water. if i remember rite it was also used for diesel fuel tanks. so it could very well be epoxy. i would check with a fibre-glass shop and see if they have ever heard of a fibre-glass resin formulated for that express purpose.
regards mike

[cat man do]

There is nothing new here, epoxy diesel and water tanks have been getting done with great success since the 70's.

Haven't heard of problems with the resin, just poor wokmanship/design.

Mike d et al, thanks for the aditional info. I am going to try to go with the West systems and no filler for the first tank, with 6oz cloth. I am making the tanks a complete seperate unit, and not using the hull as a tank wall. Wheels, the 50d cel curing is one issue I am having a hard time addressing due to the work area. I will try to figure that one out. Next weekend, I will start the first tank, and post some pics. I think coating the interior with epoxy and no filler will be the answer. I should be able to get a good mix that way. Has anyone tried using a drill with a mixer to mix the epoxy? Just wondered if this would be over kill to get a thouroughly mixed batch.

[cat man do]

Yes mate , do it all the time seing as i've used 600litres in this project so far. Good for mixing bog as well, just make sure you use a slow spinner high torque drill.

I have an 18 volt GMC battery drill that I use, cheap and gutsy.

Yep, thanks CMD. I have just the tool. A Dewalt 18v Cordless. The most used tool I have since I started working on boats

[Alan Wheeler]

Arrr DeWalt. The best damn set of tools I have ever had.
Scott, it doesn't matter too much about getting 50C. Lower temps just mean a longer curing time. Anything warmer than you have at the mo just helps. Especially seeing as you are in a colder time zone now. A good 150W or 200W light bulb would do wonders hanging inside a box. 50C is usually the max temp you ever want to go. The main reason for that is, over 50C, you will have to find away to support the work till it hardens again. The temp will soften the cure just enough to cause an unsupported area to warp or slump.

Yep, have to agree on the Dewalts. I will try the lightbulb thing. Might work if I can keep anybody from unplugging it.

[Boracay]

I searched to see what might happen if expoxy hardener were swallowed and the general sense was that this is not a good idea.
The Gougeon Brothers recomended altering the normal mixing ratio to give an excess of resin and I believe that this indicates that normally cured epoxy will contain unreacted hardener which could be expected to leech into the water (if it is used to line a water tank).
I would be happy myself to shower and to wash dishes in water from a properly built epoxy lined tank but drinking water from the tank over an extended period of time could result in the ingestion of a quantity of epoxy hardener.
I am intending to make any water tanks that I build competely removable so that I can take them ouside the boat and use high pressure water or steam cleaning to clean them.
Remember that some cruises go over three years. Thats a long time to be drinking water of questionable quality. The health impacts may be obscure and easily confused with other problems.

[cat man do]

Originally Posted by cat man do

There is nothing new here, epoxy diesel and water tanks have been getting done with great success since the 70's.

Haven't heard of problems with the resin, just poor workmanship/design.

And i'll say it again., of course if you can't count to 5 or 3 or 2 or whatever mixing ratio your resin is, and can't mix it properly, well don't play boatbuilder.

Dave

[Alan Wheeler]

Chris, if there is ever uncured hardener in a mix, a simple wash with Vinigar will desolve it away, then a good flush of fresh water to remove the vinigar. Hardener is an irritant. It stops a chemical in our bodies and our immune system basicaly attacks itself. But it does have to be in a quantity. A very small trace of it in water over years would simply pass right on through us. There are more toxins in plastic drinking containers than epoxy containers.
Having said all that, having a slightly hardener starved mix may be OK and certainly the Gougeon Brothers should know. But I also state here, that playing with that ratio is not something to do loosly.
I suggest that instead of playing with the ratio, a different sytem is used. Like a 2:1 for instance. There is usually less of a tolerance required in low ratio mixes. Teh higher the ratio, the more spot on the mix has to be and the more "user unfriendly" the hardener tends to be. The hardener being more concentraded can be very toxic to us if it is in contact with our skin.

[Stevens 47]

I spoke to the Jeffco engineer today. The resin used in potable water tank construction should be approved the NSF the standard

NSF/ANSI 61-2005
Drinking Water System Components - Health Effects
NSF International

This Standard is intended to cover specific materials or products that come into contact with: drinking water, drinking water treatment chemicals, or both. The focus of the Standard is evaluation of contaminants or impurities imparted indirectly to drinking water. The products and materials covered include, but are not limited to, process media (carbon, sand, etc.), protective materials (coatings, linings, liners, etc.), joining and sealing materials (solvent cements, welding materials, gaskets, etc.), pipes and related products (pipes, tanks, fittings, etc.), mechanical devices used in treatment/transmission/distribution systems (valves, chlorinators, separation membranes, etc.), and mechanical plumbing devices (faucets, endpoint control valves, etc.).

Point-of-use and point-of-entry drinking water treatment devices are not covered by the scope of this Standard. Fire hydrants are not covered by the scope of this Standard

The Jeffco product that complies with this standard are epoxy resin 1405 with a 4105 bb hardener or a epoxy resin 1409 and a 4102 hardener. http://www.jeffcoproducts.com/

I use these guys because they are local for me.

Jack

Thanks Jack, I will check them out. The first tank will be the exeriment. The vinager wash is a definite yes, and letting water sit in the tank for a few weeks, then having it tested will be the deciding factor. The first tank will ultimately be used for a holding tank, but if the water test comes back safe, no reason to change procedures for the rest. If it doesn't I should have some good info to post on what went wrong. In understand the possible long term effects, but if chemical content measured in the tank in the first 30 days is in an acceptable range, it is unlikely to get worse.