Epoxy over two part polyurethane foam

[coopec43]

It's not my day!

The computer is playing up and I'm getting a little confused by robwilk who as far as I was concerned I was responding to on two different threads. Over about twenty comments I thought I was getting to know Rob but it turns out I am corresponding to robwliks37 of San Diego and robwilks of Wellington NZ. and I didn't realise it

[Wotname]

Originally Posted by coopec43

Wotname

I tried to copy the actual statement in their brochure where it says " Suitable for collection and storage of potable water" but nothing is working this morning.

http://www.crommelin.com.au/assets/U...umen-Paint.pdf

Regarding epoxy for drinking water I'm quite sure you and John61ct are correct. (I don't know about robwilk37 as he is way over my head!)

Apparently epoxy is OK for storage of water if it is cured properly in optimal conditions but who of us can do that on a yacht?

The Gougeon Bros (WestSystem) do not recomend it.


Why we don’t recommend building an epoxy composite tank for potable water

We have adopted the broad policy of not recommending epoxy for drinking water tanks because of regulatory and safety issues. The potential problems outweigh the benefits. To date, none of Gougeon Br......

https://www.epoxyworks.com/index.php...nk-guidelines/

OK, re-read the link more carefully and as you say, it is suitable for potable water storage so that seems to settle that question.

As for the epoxies, I only going on memory here but I seem to recall that run of the mill boat type epoxies aren't certified as food safe (as you and others allude to) but there are suitable food safe epoxies around that are applied at completion to provide a food safe surface - but I could be wrong!

[robwilk37]

just to be clear, "food-safe" and "water storage safe" are two very different things. one assumes incidental contact and the other continuous contact. even when you find a tank coating that is NSF certified for potable water, its usually for large volumes (so any potential contamination is diluted below the allowable spec).

so big picture, you build-in the tank (adding structure and stiffness to the hull, and effectively double-hulling assuming its below the waterline) then have custom NSF certified bladders made to fit.

[coopec43]

Well the AS/NZS 4020 sets out the standard for potable water

Requirements on the products which come into contact with drinking water, such as pipes and fittings, have been outlined in AS/NZS 4020:2018, Testing of products for use in contact with drinking water.

Crommelin claim to meet that standard.

But let's face it if we get our supply out of a river or reservoir will it be pure? Sadly it will probably be contaminated with herbicides/pesticides, animal faeces. So long as the concentration is low I assume it will not matter. But some of the chemicals in higher concentrations can be harmful such as styrene.

Chronic (long-term) exposure to styrene in humans results in effects on the central nervous system (CNS), such as headache, fatigue, weakness, and depression, CSN dysfunction, hearing loss, and peripheral neuropathy.

[john61ct]

Yes there's food-safe for floors, walls, counters, fridges.

Drinking water tank is at another level.

[robwilk37]

[QUOTE=coopec43;2975021]Well the AS/NZS 4020 sets out the standard for potable water

[SIZE=1]Requirements on the products which come into contact with drinking water, such as pipes and fittings, have been outlined in AS/NZS 4020:2018, Testing of products for use in contact with drinking water. [/SIZE

not trying to beat a dead horse, but again "contact" and "storage" are not equals. the problem as i understand it with epoxies are bisphenals, amines and phthalates. made worse by "hungry" water off the RO. ive asked some pretty smart people if i can just install a charcoal filter post tank and remove these volatiles but cant get a straight answer. its ironic that the pure product off the membrane actually acts as a weak solvent, trying to pick back up all the crap you just worked to strip out of it.

[Wotname]

Crikey, so of you can complicate things however here is Jotun epoxy designed for potable water tanks - at least as far as BS 6920-1:2000 is concerned - I dunno if that is applicable to your average small boat tank or not.

https://www.jotun.com/ww/en/b2b/pain...kguard-dw.aspx

[robwilk37]

Originally Posted by Wotname

Crikey, so of you can complicate things however here is Jotun epoxy designed for potable water tanks - at least as far as BS 6920-1:2000 is concerned - I dunno if that is applicable to your average small boat tank or not.

https://www.jotun.com/ww/en/b2b/pain...kguard-dw.aspx

yep, been down that rabbit hole too. bs6920 assumes tankage of 10,000L minimum, or so ive been told. also theres a decontamination protocol before service, which implies contaminates are present. i couldnt get an answer out of jotun when i talked to them a couple years ago, or any of the tank coating formulators for that matter. they just didnt have answers for such small tanks.

and it gets a couple levels more complicated when you tell them its RO water you want to store, think one guys head exploded...

[Wotname]

^^ thanks robwilk37, I get it - it's complicated

[coopec43]

Originally Posted by Wotname

OK, re-read the link more carefully and as you say, it is suitable for potable water storage so that seems to settle that question.

As for the epoxies, I only going on memory here but I seem to recall that run of the mill boat type epoxies aren't certified as food safe (as you and others allude to) but there are suitable food safe epoxies around that are applied at completion to provide a food safe surface - but I could be wrong!

Food Safe Epoxy

The FDA’s Title 21, Volume 3 report states that food safe epoxy does, in fact, exist. While an epoxy coating is generally not associated with a place in the kitchen, several brands have come out with new and im

AND
Epoxy, when cured, is generally food safe, as long as it is in compliance with the FDA’s thorough regulations. Many companies will have their epoxy labeled as “food grade epoxy coating,” thus signaling that it is safe to use on surfaces that come into contact with food.It is imperative that an epoxy has this label if there is consideration in having it come into contact with food. The widespread nature of this FDA-approved ingredient list allows individuals to seal virtually any surface without fear of toxicity or harmful effects.

https://epoxycountertopdiy.com/food-safe-epoxy/

[john61ct]

Originally Posted by coopec43

The FDA’s Title 21, Volume 3 report states that food safe epoxy does, in fact, exist.

Maybe you're just not reading others' comments?

Again, there's food-safe for floors, walls, counters, fridges.

Drinking water tanks are at another level.

[coopec43]

Originally Posted by john61ct

Maybe you're just not reading others' comments?

Again, there's food-safe for floors, walls, counters, fridges.

Drinking water tanks are at another level.

Whatever....

[GILow]

Hmmm..... I thought I had posted on this one.... try again...

So, great discussion.

For the record, my epoxy supplier claims that the area of concern with epoxy and water tanks are the things they use to accelerate the curing process, and so has recommended a super slow cure epoxy.

Interesting theory, I’d be keen to hear if anyone has heard something similar.

I am still considering my options, but right at the moment I am favouring either the stuff Coopec43 mentions or, more likely, a product from sika that has AS4020 compliance for potable water STORAGE. (Not just contact). I am planning to call each of the vendors today to discuss. I’ve found it very good if you blast your way past the sales team with a couple of curly questions and talk to the guys behind the scenes who actually know how the product works and are not hell-bent on selling you some to boost their sales figures.

[GILow]

Follow up to this....

I have just been on the phone to the Sika technical guys and they emphatically state that their Sika 560 product is suited to this application.

They got a bit... um... scratchy, when I asked if it would be safe in my proposed application, citing the AS4020 certification, but they relaxed when I explained that I just wanted to be sure that the certification still applied if I were to use it the way I am proposing.

They said, absolutely, yes, this was an appropriate application of the product and was within the certification parameters.

And the real bonus is that Bunnings stock it, as do a few of my favourite building supplies places.

Matt

[john61ct]

Great, Sika's the bee's knees

but wrt the topic, not an epoxy