Water tank and epoxy coating

[BlueNoser17]

Hi Everyone

My apologies if this question has been asked many times before but I was unable to find an answer to my specific question.

I am trying to find out whether or not West Systems 105 Epoxy is “okay” for coating the inside of my water tank.

Some specifics:
- we are “rebuilding” a water tank in our bow which is epoxy covered wood. Two sides are the beveled hull in the bow (with a further chain locker in the front and wooden bullhead in the back)
- this is the second water tank (aluminum under the settee) and we only use it for showers, washing and possibly brushing our teeth. Not planning on drinking but perhaps a possibility if safe
- we are currently rebuilding the tank with various new pieces of export coating wood and mar fibreglass where needed to replace older rotten wood and reseal the tank. It is epoxy coated originally and after the repairs we intend to apply a coating of 105 throughout the interior of the tank
- it has an aluminum inspection plate with a rubber seal

I have read a number of articles regarding (difficult to find) food grade epoxy coatings for water tanks. However, I am unable to see if Weat System 105 is itself okay to use. I’m aware that this my just be a liability concern and it is perfectly fine but would like to hear some more informed opinions and views

Thank you
Mark

[ggray]

Call WEST tech support

[Lepke]

You can. I built some fiberglass boats in the 70s with built in water and fuel tanks. And they're still going. You need cloth so the epoxy is thick enough over the wood to last. I use 2.0 rsm.

It takes some effort to make the water taste good. It's easier to put a potable water tank coating on last.

[BlueNoser17]

That sounds reasonable. The areas that do. It need repair have thick fibreglass already and the replacement pieces we are inserting we have both epoxied and will be overlaying with glass. I am inclined to lightly sand the whole inside of the tank and roll on a couple of layers of 105 just for redundancy though if it is potable(ish)

[rslifkin]

West won't officially call their epoxies potable water safe. But there are epoxy based coatings out there with the certification. Aquatapoxy A61 and A6 are both certified for tanks of 50+ gallons. I've only used the A61 personally, and it's extremely thick and probably the most unpleasant substance I've ever tried to paint onto a surface. But it did leave a nice, slick, white coating when done.

[BlueNoser17]

Thank you RSLifkin

Considering the price of the potable epoxies and the fact that we don’t plan on consuming the water, I am inclined to just coat the insides with another couple layers of 105 and leave it like that for now. Can easily take off the top and apply “potable “ epoxy at a later time

[GILow]

I’m working from memory a little here, from conversations with product vendors, but if I recall correctly the main problem with epoxies and water is not the epoxy itself but the accelerants used in the hardener. These leech out over time.

Personally, having built my water tanks from plywood and epoxy, I’d grit my teeth and spend the extra now. Surely there isn’t all that great a volume of epoxy involved? My pair of 350 litre tanks used only a few kg.

Failing that, there are various coatings you can apply over the top. Here in Aus anything rated to AS4020 is supposed to be safe. I used an AS4020 certified product from Sika to coat my tanks as an additional safety measure but for the next boat I’ve decided to stick with the proper product from Jotun, one less costing.

Adding such coatings later will be difficult at best, trying to get a good cover while reaching in through an inspection port probably won’t work well. Also, who’s to say if whatever it is in the epoxy that isn’t safe won’t leech through the costing over time anyway. Seriously, I’d use the good stuff now, just for peace of mind.