Integral water tank with fibreglass

[Benny]

Hi everybody, I need some advice. I'm on a steel narrowboat and all the integral tanks i've read about on here have been vactanned and sometimes bitumenned. Well I've lifted mine and it's been lined in fibreglass. The fibreglass on one side has peeled off the steel and rusty steel resides behind. It also lacks an insulator at the sides which I'm assuming it needs? The ceiling of the tank has bitumen on the steel, no fibreglass. The bottom of the tank is fibreglassed and probably stuck fast. Another thing I've noticed is that the outlet pipe is quite high above the bottom of the tank, so there will always be left over water.

 

So what do I do?

 

I'm assuming I start by peeling the sides away and going to town with a wire brush and vactan. Then do I insulate the sides? Do I reapply fibreglass, or just vactan/bitumen the sides? Can I lower the outlet pipe, or raise the bottom of the tank?

 

Nasty job I know, not looking forward to it. Advice much appreciated. Photos attached.

[Tony Brooks]

The sides (the angled, curved parts) are the hull so there is n need to insulate that. The flat side that backs onto the cabin is probably a bulkhead and you may want to thermally insulate that on the dry (cabin) side, not in the tank.

 

I do not like the look of the rust you show and wonder if the GRP was a bodge to seal a perforated hull. In any case the GRP should have been carried right up to the top of the tank and ideally under the "roof" of the tank.

 

I suspect the safest way forward, funds permitting, is to see if you can get a plastic or stainless steel tank made to fit into that space you it will probably mean taking the well deck floor out and then re-welding it.

 

You won't really know your options until you have got as much of the rust off and assessed the hull condition. You could end up with the whole front section re-plaited so then there would be no rust or GRP.

[David Mack]

With a tank full of water I think it is unrealistic not to expect water to get down between the fibreglass and the steel, and once there it will rust as you have found. 

By all means try and trim back the loose fibreglass, but I think you will just keep on going trying to find a firm edge where it is well bonded to the steel.

The exposed rusty steel will need to be taken back to sound metal, at which point I think you are looking at either vactan and bitumen or a suitable epoxy. Before embarking on either of those I would want to know that the remaining steel is thick enough, otherwise you are looking at replating as Tony suggests.

[Benny]

Thanks for advice. The hull had a survey and some plating in 2017. I'm sure a lot of damage can happen in 4 years tho. I'll rip as much FG out as possible, scrape it down carefully and see where I stand 

[Tony Brooks]

1 minute ago, Benny said:

Thanks for advice. The hull had a survey and some plating in 2017. I'm sure a lot of damage can happen in 4 years tho. I'll rip as much FG out as possible, scrape it down carefully and see where I stand 

 

If any plating was done where the GRP has come away that could be the cause but GRP is still not good.

[Benny]

6 minutes ago, Tony Brooks said:

 

If any plating was done where the GRP has come away that could be the cause but GRP is still not good.

I've just had a look and the plating is indeed where the grp has come away. Let's just hope more damage hasn't been done below the plate. 

[Tony Brooks]

In which case as you pull the GRP away you may well come to a part that did not get hot enough to break the bond between steel and GRP.  If so you could clean off as much rust as possible fair the existing GRP so its edge apers down to the steel and score the steel with a  course grinding disk. Then apply more GRP. I still don't like the idea but it may be the cheapest way.

[Tracy D'arth]

Sell it.

[Benny]

 

4 minutes ago, Tony Brooks said:

In which case as you pull the GRP away you may well come to a part that did not get hot enough to break the bond between steel and GRP.  If so you could clean off as much rust as possible fair the existing GRP so its edge apers down to the steel and score the steel with a  course grinding disk. Then apply more GRP. I still don't like the idea but it may be the cheapest way.

Ok thanks Tony. I'll give it a go this week and post results 

 

1 minute ago, Tracy D'arth said:

3 minutes ago, Tracy D'arth said:

Sell it.

 

Can't be THAT bad can it? 

 

[Tracy D'arth]

5 minutes ago, Benny said:

 

Ok

 

Can't be THAT bad can it? 

 

Reserve judgement until you find out why someone went to an awful lot of trouble to cover up the inside of the tank. I think you will find that the hull is corroded away badly.

Big question,   "Why was the hull over plated"

[Ex Brummie]

After doing all the above, you are still faced with the high outlet. My tank is the same, with the outlet at the top of rear bulkhead. This is fitted with a dip tube that goes to the bottom of the tank like yours has got by the look of it. Your pump will lift easily over that height. It has an advantage that if your pump should freeze and leak, and the tank is not isolated, then you will not find your tank emptied into the cabin bilge.

[Benny]

17 minutes ago, Ex Brummie said:

After doing all the above, you are still faced with the high outlet. My tank is the same, with the outlet at the top of rear bulkhead. This is fitted with a dip tube that goes to the bottom of the tank like yours has got by the look of it. Your pump will lift easily over that height. It has an advantage that if your pump should freeze and leak, and the tank is not isolated, then you will not find your tank emptied into the cabin bilge.

That's really useful thanks. I wondered why it was shaped like that.

[Man 'o Kent]

Many years ago I had cause to investigated a product under the trade name Irathane, (in truth for quite a different purpose), but I was impressed and in my dotage it has occurred to me that it might just do the business on water tanks.

 

It comes in various formulations some specifically intended for domestic water. It is mainly a two pack spray-on material but if memory serves can also be brush applied.

In a perfect world the inside of the water tank would be grit blasted down to bare metal and then ideally Zinc sprayed followed by a coating of a suitable grade of Irathane.

Clearly the subject would need further investigation but does offer an alternative long term solution.

[Benny]

What product would I use for the fibreglass? Presumably some kind of food safe epoxy or PU?

 

[Tony Brooks]

Er - polyester resin and harder plus glass chopped strand glass fibre mat. Loads of rubber gloves, stippling brushes, GRP roller, mixing pots and stirrers and maybe to finish off some glass fibre scrim cloth. Old long sleeved shirts, hats etc. because you are likely to get covered doing that job. Oh and lots of Acetone solvent to clean yourself, working area and your tools

 

The water might be tainted by the resin and hardener for some time. I am not sure how epoxy resin would stick to polyester resin so as the existing GRP is probably polyester best stick to that.

Edited May 2, 2021 by Tony Brooks

[Benny]

21 minutes ago, Tony Brooks said:

Er - polyester resin and harder plus glass chopped strand glass fibre mat. Loads of rubber gloves, stippling brushes, GRP roller, mixing pots and stirrers and maybe to finish off some glass fibre scrim cloth. Old long sleeved shirts, hats etc. because you are likely to get covered doing that job. Oh and lots of Acetone solvent to clean yourself, working area and your tools

 

The water might be tainted by the resin and hardener for some time. I am not sure how epoxy resin would stick to polyester resin so as the existing GRP is probably polyester best stick to that.

 

Thanks for this Tony. Will the Polyester resin stick ok to vactanned/bitumenned metal? Should I go all the way around the water tank ceiling included? Or should I water bitumen the ceiling as has previously been done? I am also wondering if it would be better to vactan and bitumen as much of the sides as possible so I can keep a check on it easier.

 

I'm guessing if there's not a water-potable Polyester resin, I'm better off not drinking from the tank for a while.

[Tony Brooks]

First of all they do/have made GRP water tanks so once its cured I THINK it will be fine.

 

As far as your other questions go I think the resin will simply dissolve bitumen and I don't have the technical data to say anything about Vactan. You don't want the new GRP falling off so I think I would accept its a bodge and apply it to course disk sanded steel.

 

If you can get the GRP off I think you would find it far easier to apply Vactan and bitumen or an epoxy coating BUT it all depends upon what the hull is like when its de-rusted and how well you can de-rust it. I think @blackrose knows of a surface tolerant epoxy and he might advise.

[Benny]

8 minutes ago, Tony Brooks said:

First of all they do/have made GRP water tanks so once its cured I THINK it will be fine.

 

As far as your other questions go I think the resin will simply dissolve bitumen and I don't have the technical data to say anything about Vactan. You don't want the new GRP falling off so I think I would accept its a bodge and apply it to course disk sanded steel.

 

If you can get the GRP off I think you would find it far easier to apply Vactan and bitumen or an epoxy coating BUT it all depends upon what the hull is like when its de-rusted and how well you can de-rust it. I think @blackrose knows of a surface tolerant epoxy and he might advise.

Ok that sounds good thanks ?

[Man 'o Kent]

An added point to consider: Repairing GRP under these conditions would be an almost impossible nightmare, at the very least you would need a supply of small chimney sweeps to clean it out but I hardly think the Reverend Charles Kingsley would approve.

 

It will be all but impossible to get a new GRP lining into that space that is entirely waterproof, GRP is to some extent hydroscopic even when laid up in perfect conditions.

 

You really do not want to have to go inside that tank! Here is where grit blasting, ideally Zinc spraying and then an Irathane coating would be a permant solution without the need for anyone to go inside the tank.

[Tony Brooks]

1 hour ago, Man 'o Kent said:

An added point to consider: Repairing GRP under these conditions would be an almost impossible nightmare, at the very least you would need a supply of small chimney sweeps to clean it out but I hardly think the Reverend Charles Kingsley would approve.

 

It will be all but impossible to get a new GRP lining into that space that is entirely waterproof, GRP is to some extent hydroscopic even when laid up in perfect conditions.

 

You really do not want to have to go inside that tank! Here is where grit blasting, ideally Zinc spraying and then an Irathane coating would be a permant solution without the need for anyone to go inside the tank.

 

I agree but not quite so sure about Irathane. With decent prep and more readily available epoxide coating should do. I suspect the OP may not have the funds for professional grit blasting etc so it could be trying to do the best of a bad job.

 

@Benny, any gaps under the back of a double bed where you could shoehorn in a plastic tank?

 

 

 

 

[Benny]

@Man 'o Kent That does sound like the best (and easiest) solution by far but I'm guessing it's pricey, in the thousands? If I get desperate I may consider it. 

 

I think taking the grp on the sides away and seeing where I stand is the best place to start. I'm happy if I can maintain it every couple years and prevent further degeneration. I'm reluctant to grp up the sides unless necessary, as I'm sure it'll make it harder to maintain and create a potential water trap behind when it peels away. Like I say I'll re-evaluate after a scrape. 

 

@Tony Brooks it's a 45 footer so cabin space is precious! It would be tricky to get much volume anywhere else on the boat. I will think about it though, as it would make life easier! 

 

[Tracy D'arth]

Tom Rolt had a tank on the roof,   just saying.

[Benny]

21 minutes ago, Tracy D'arth said:

Tom Rolt had a tank on the roof,   just saying.

I wouldn't have thought of the roof, seems a bit top heavy? I would consider anything tho ?

[ditchcrawler]

13 minutes ago, Benny said:

I wouldn't have thought of the roof, seems a bit top heavy? I would consider anything tho ?

Don't need a water pump then, gravity feed to the taps. Naff shower

[Phoenix_V]

flexible tank/liner?