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Integral water tank, modifying.


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At some point I am going to have to bite the bullet and tackle my integral tank.

I doubt the lid has been off this tank for many years, in fact the last but one surveyor actually missed it, stating there was no access when in fact there is, but the deck/lid is so worn you would be forgiven for not seeing it.  

The well deck is quite corroded owing to the previous owner fitting some of that non slip ribbed semi permeable stuff that traps surface water, so, my plan is to have the entire deck cut away which will also make seeing inside the tank and doing whatever remedial work is necessary much easier. 

The issue is what to do with it next.  

I'm quite taken with the idea of having a separate tank or tanks installed, plastic or s/s.  But I do not want to then have a new deck welded back on with either limited or no access to the new tanks.  Normally with free standing tanks you would have access through the cabin via the front bulkhead.  Creating such an access on my boat would be complicated owing to the position of the gas heater and the water pipes, all of which would need re routing.  So I am trying to think of a way to access the entire void from the well deck.  

Obviously an engine bay is accessed this way so it ought to be feasible, but being at the bow it is of course an awkward shape.  It's also constrained by steel bow lockers either side. (I wish I had a photo as I can't very well describe this.)  But as a principle I wonder if anyone has experience of this sort of arrangement.  I do recall one of the members telling me he had a removable well deck  but IIRC he said he could never get it totally watertight.     

Any ideas/comments would be welcome.

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7 minutes ago, Tony Brooks said:

how about a flexible tank installed through the current tank's inspection plate? Decent made to fit ones seem to be expensive but should last along time.

This is what I was going to do originally but I'm keen on the idea of having open access.  I should explain that the existing tank is huge, absolutely huge, and I think when I have exposed the entire void I won't want to fill it with a free standing tank, it would be more useful as additional storage.  

I think plywood boards might be the most practical way if I can ensure the surface water drains overboard somehow.  I've seen older boats with plywood well decks but only of the "wet bilge" design. 

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Take the whole tank back to bare metal. Sounds like you will be doing some serious cutting and welding so needle gunning or even better shot blasting the tank would be appropriate. Then paint with epoxy, I suggest the stuff from Reactive Resins. Should last many many years.

Integral tanks have so many advantages that I really don't understand why so many people want to get rid of them. Ensuring a good seal on the access hatch is the only complication.

A huge water tank is a very good thing to have, especially if you are, or plan to be, a liveaboard.

............Dave

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I would try to avoid plywood. How about giving the whole thing a good clean and paint then welding a new deck on it but with a big inspection hatch and a ring of countersunk bolts on it giving access to a flexi tank of some sort? I think it will be a lot of work whatever you do but a better job than an integral tank (In my opinion)

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1 minute ago, Chewbacka said:

I don't understand why people don't like an integral tank.  Basically what's the difference between benefit of a flexible  tank over a mild steel tank that is epoxy painted??  

From what I have heard and read very few are treated with epoxy paint inside. I hear people saying that blacking is no longer classed as suitable for Potable water tanks.

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Just now, ditchcrawler said:

From what I have heard and read very few are treated with epoxy paint inside. I hear people saying that blacking is no longer classed as suitable for Potable water tanks.

Agreed, most were coated with blacking which I think are now classed as slightly possibly carcinogenic.  But that aside, I still don't understand why people ordering new boats want a separate stainless or plastic tank when for less you can have an integral tank with epoxy coating which will make best use of space=bigger.

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How flexible is cured epoxy?

Integral water tanks tend to be at the front of narrowboats where they may be subject to impacts and actual denting. If the epoxy failed would not rust creep under it and lift it off just like other paint.

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Integral tanks. I think the risk of corrosion from both sides of a piece of steel is just too great. The chances of anyone maintaining the inside of a tank is really not that good. I have wrestled a few galvanised tanks out of loft spaces that have rusted right through and galvanising should be a better bet than epoxy I would think.

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23 hours ago, Bee said:

Integral tanks. I think the risk of corrosion from both sides of a piece of steel is just too great. The chances of anyone maintaining the inside of a tank is really not that good. I have wrestled a few galvanised tanks out of loft spaces that have rusted right through and galvanising should be a better bet than epoxy I would think.

Drop a nail or bit of copper and the zinc around it will rapidly corrode away leaving exposed steel.  The steel used for galvanised tanks is probably only 1mm thick or less, so it will last just a few years once the zinc has gone.  People pay huge money to epoxy coat the outsides of their boat with very good results, so inside a tank where there are no bangs and scrapes should be much better.  That said, I would still open the tank every few years and check it.  It would be interesting to hear if any body on here has had an epoxy coated tank rust out.

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I've just discovered the exchange I had a few years ago with the owner of a boat similar to mine who had a "deck access" tank.  

The builder at the time offered two options for a free standing tank, one being the conventional arrangement with access from the cabin below the bow doors, the other was via a removable well deck which was two steel plates.  Unfortunately I don't have any more details, I've emailed the member concerned but he hasn't been active on the forum for a while.  I've certainly never seen a boat with this arrangement, it sounds as though no-one else has..?

  

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  • 4 weeks later...

Just about to decide how to coat the inside of my integral steel water tank. Have cleaned out all the rust bubbles with a pressure washer and treated all the surfaces with Fertan. Have been led to Armourguard PW and trying to work out the quantity and tin size to mix just enough to get on before it cures (3 x 1 litre pots seems favourite at present). Does anyone have any experience with Armouguard PW ? Do I need to use their pfrimer or will the Fertan rust treatment suffice ? Have also spoken to Antel Paints who have a solvent free 2 pack epoxy coating available. Again has anyone out there used it ? Any advice appreciated. Thanks

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Interesting. This is my summertime job reseal the water tank. I did email armourguard his response was. 

Once cleaning and abrading the entire surface, you can apply :

1 x coat of Armourguard STfollowed my 2-3 coats of Armourguard PW.
If you have pitted areas you would like to smooth over, you can apply our
Easy Fair epoxy filler in between the Armourguard ST coat and 1st coat of
Armourguard PW.

I've attached the data sheets for all 3 products. If you require a quote,
please let me know the area and we can work that out for you.

Please also note that we haven't tested rust treatment compatibility with
our Armourguard ST. Although it should be fine, we would just recommend
that you try a test sample first to ensure it bonds as it should

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