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Vactan what to overcoat with in a water tank, for safe drinking water


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I am currently helping my mum renovate her, we are both complete novices. We are currently doing the metal water tank, we have cleaned it out with a wire brush and applied 4 coats of vactan and are aware we need to overcoat it with 2 pack polyurethane paint but are unsure of which one to go with for safe drinking water. Sorry if this topic has been covered before i couldn't find it. Any advice we would be grateful for. Thanks 

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2 pack polyurethane?  Did you mean 2 pack epoxy?  Not sure if either is good on top of Vactan which is a vinyl finish. Of the two I would go for epoxy but water tank, no taint, bitumen is what is generally used straight onto clean steel. 

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Not sure why you were told 4 coats of vactan was a good idea? One coat should do the job of rust conversion, after that, a decent 2 pack epoxy or water tank bitumen should do, leave for as long as possible to dry off...

Weeks rather than days if you can as the water underneath is still cold.

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Seems a shame to paint expensive water potable epoxy over Vactan. I've never heard of a two part epoxy that's designed to be applied over a rust converter, especially the Vactan type which is based on a single part polymer matrix. You're basically using a highly durable product over a much weaker one. Epoxies serve as their own primer and surface prep requires mechanical removal of the rust, not chemical conversion. I don't know why so many people can't be bothered to read the product' technical data sheets and plan the job properly? 

 

If you've already painted Vactan in your tank (why 4 coats I also don't understand) then your best bet is to forget about epoxy and just put a few coats of bitumen on top. 

Edited by blackrose
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Thank you for your replys. The vatcan instructions told my mum to do 4 coats. The vatcan website recommended 2 Pack polyurethane paint. When we bought the boat we were told the water tank was in good condition (we took someone who lives on a narrow boat to inspect and advise they didn't inspect the basics, now we know we should of inspected ourselves) it was awful, after draining it, it was badly rusted huge lumps so we didn't have clean steel. Another narrow boater recommended vatcan to my mum and she though it was a one and done process but i read into it and realised vatcan recommend an over coat. Can we paint water tank bitumen over it, do you think its a good idea? Should we try and strip some of the vatcan. 

An old friend of my mums used to work on large boats suggested a cement layer but will that weigh the front of the boat down, will it crack it she dings the boat on a lock? 

Sorry for all the questions my mums on a budget and trying to do this while still working full time. We have some boating experience but nothing in the way of renovation, also while docked in a marina some people say one thing some say another so I wanted to try and get a good comprehensive view of all options/advice before making any more decisions. Thank you all. 

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21 minutes ago, Rebekah said:

An old friend of my mums used to work on large boats suggested a cement layer but will that weigh the front of the boat down, will it crack it she dings the boat on a lock? 

 

Yes, large boats' tanks are cement washed as protection, but it is not a cement layer in the conventional sense. It is more like a couple of coats of thin cement slurry, allowing it to harden but not dry between coats. I would not weigh the front of the boat down in any discernable way, but it would be prone to cracking if/when the boat hit something hard.

 

I am not going to comment on how good an idea the various coating options are, but I fear whatever you do may not be long-lasting because of the suboptimal surface prep (not your fault) and the four coats of Vactan, so bitumen will do the job for now.

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I think bitumen sounds like the way to go. We did spend many hours with a drill and angle grinder with wire brush attachments taking off as much rust as possible. I understand that having the tank replaced is probably a sensible option but its not in the budget currently. Thank you for your advice. 

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Assuming that the tank is integral in the bow, replacement is too horrendous to consider.

I would give it 2 coats of water tank bitumen, it should last at least 5 to 10 years in my experience, may be longer with the Vactan underneath. I doubt that the bitumen will peel off, its very tenacious stuff. But you are not doing what has been done for years, that is bitumen onto clean steel.

Removing the Vactan is not an option and even then you would have to needle gun the steel back to bright all over, corners included, which is  a hell of a job not to be contemplated.

I do know of boats with similar tank that are 50 years old, never been touched,  and the owners just avoid looking inside!

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Yes it is integral in the bow hence why its out of the budget. I think it had not been looked at for many years. On the trip bringing it back from where we bought it we did use the water, boiled thankfully then realised it started coming out brown, ran it for an hour still brown. You are right i don't think we should attempt to bring it back to clean steel. Thank you for your input 

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Alternatives.

 

You can get shaped bag tanks that go inside the existing tank. The connections need to be fitted of course, a bit of work, but my experience is that they crease and eventually split. They hang from supports around the top.

 

Or, better, get a rigid plastic tank custom made, not too expensive, There are several UK companies,  and cut the rear wall of the steel tank out and maybe the front bow floor, to get it into the tank space.   Depending on the boat this may mean a smaller capacity.

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I seem to recall previous threads where folk recommended Vactan as a final coating for water tanks. But if the manufacturers recommend overcoats that would be better. 

Bitumen used to be a very common treatment for drinking water tanks, but following a change in the rules, most bitumen coatings are no longer approved for contact with potable water. So check the product you are proposing to use.

As long as the manhole seal is effective and you practice reasonable hygiene when filling up there is no reason why you can't continue drinking water straight from the tank. Rust discolouration may look a bit off-putting, but it won't do you any harm.

I think fitting a bladder or smaller tank inside the existing tank is completely unnecessary, as well as being costly and disruptive.

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Apologies for hi jacking the thread, however I have used 2 pac epoxy paint recently on my tank and have left it for a week so far to dry/cure. 
 

Wanted to start using again but there are a couple of small spots that are still tacky. 
 

Guess those bits weren’t mixed properly. 
 

Could I use something like this to solve the issue https://www.amazon.co.uk/UPol-Hardener-Activator-Primers-Repairs/dp/B073JBCMMC

 

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26 minutes ago, Owls Den said:

Apologies for hi jacking the thread, however I have used 2 pac epoxy paint recently on my tank and have left it for a week so far to dry/cure. 
 

Wanted to start using again but there are a couple of small spots that are still tacky. 
 

Guess those bits weren’t mixed properly. 
 

Could I use something like this to solve the issue https://www.amazon.co.uk/UPol-Hardener-Activator-Primers-Repairs/dp/B073JBCMMC

 

 

No paint expert in any way, but I think the chances of that working would be slim unless it is for epoxy AND it is the same chemical as used in the original paint.  Although epoxy hardens by a chemical process, I think it still has solvents in it and being in a water tank I suspect this may be more to do with solvent fume heavy air preventing further evaporation. I would try a fan heater directed into the tank for a while to see if that sorts it. If not I would suggest you ask the manufacturer.

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43 minutes ago, Owls Den said:

Apologies for hi jacking the thread, however I have used 2 pac epoxy paint recently on my tank and have left it for a week so far to dry/cure. 
 

Wanted to start using again but there are a couple of small spots that are still tacky. 
 

Guess those bits weren’t mixed properly. 
 

Could I use something like this to solve the issue https://www.amazon.co.uk/UPol-Hardener-Activator-Primers-Repairs/dp/B073JBCMMC

 

Scrub some properly mixed epoxy into the tacky bits?  Try hanging a hand lamp, mains of course, in the tank for a while to get the temperature  up.

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1 hour ago, Tracy D'arth said:

Scrub some properly mixed epoxy into the tacky bits?  Try hanging a hand lamp, mains of course, in the tank for a while to get the temperature  up.

I don’t have any epoxy paint left. V expensive and had to travel far to collect as postage fees were ridiculous. 
 

 

1 hour ago, Tony Brooks said:

I suspect this may be more to do with solvent fume heavy air preventing further evaporation

It’s a 1000l tank with a large hatch so airflow isn’t the issue I don’t think. 

45 minutes ago, ditchcrawler said:

If the steel tank has not rusted through and leaking its not going to hurt you even if its red rust, Steel and iron were  used for water systems for years, now its mainly plastic mains pipes 

The romans used lead! 

Thanks for the replies I’m hoping to source the activator part of the epoxy without buying the paint too. I’m 99percent sure these small tacky areas are from non mixed paint that has been applied by some fool (me) from the paint lid or something along those lines.

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5 hours ago, Rebekah said:

Thank you for your replys. The vatcan instructions told my mum to do 4 coats. The vatcan website recommended 2 Pack polyurethane paint. 

 

2 pack polyurethane? Ok then forget what I've said as I thought we were talking about 2 pack epoxy. I don't have any knowledge of 2 pack polyurethane paints. Are you sure it's suitable for potable water tanks?

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4 hours ago, ditchcrawler said:

So did we, I wonder how much actually leaches out of it into water? one for the chemists out there

 

A lot, in soft water areas AIUI. So much so that it is now illegal to use.

 

In hard water areas a patina forms on the inside of the pipe that prevents the lead leaching into the water. 

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Another thumbs for acothane DW. Not cheap but did an excellent job. Took nearly 4 litres to do a 1350 litre bow tank. I added the activator to the pot, mixed it thoroughly then decanted it into a fresh paint kettle and mixed it again. No problem with unmixed paint.

BUT you can’t hang around as the mixed product cures pretty fast. 

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Further to my above post. I had two 2 litre pots of paint, rather than one 4 litre.

I used one 2 litre pot at a time. 
if you mixed a whole 4 litre pot you would never have enough time to use it in a water tank before it cured to much. 
Just a little tip if anyone is thinking of using it. 

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27 minutes ago, plato said:

Further to my above post. I had two 2 litre pots of paint, rather than one 4 litre.

I used one 2 litre pot at a time. 
if you mixed a whole 4 litre pot you would never have enough time to use it in a water tank before it cured to much. 
Just a little tip if anyone is thinking of using it. 

 

So true if it is anything like West Systems epoxy. The larger the volume, the less heat can escape from that volume, so large shallow trays tend to stay workable for longer than smaller deeper ones.

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