Sealing Inspection Cover For Integral Water Tank

[alan_fincher]

We have an integral steel fresh water tank that gues under most of the front well deck, (and forward under the gas locker).

 

It has a large access hatch at the front of the well deck, (bigger than many), and this is simply a square steel plate (5mm probably) which overlaps the hole by maybe 3cm all round. It is drilled and countersunk, and bolt go through into tapped holes around the side of the inspection hole.

 

The plate sits proud of the foredeck by it's own thickness - crude but functional!

 

There is every evidence because of heavy pitting around both surfaces, that this has not been well sealed in the past. Our surveyour said that silicone was not an appropriate seal, and on the last opening a mastic putty like 'Glasti Cord" was used, but this was not really a success, as it is designed not to set, and hence gets squashed out by people walking on it.

 

I'm now not really sure what to use for the best seal, (obviously I want to keep rain and towpath muck out of my drinking water ) .

 

Suggestions, please!

 

Alan

[Nickhlx]

Make up a (large) gasket out of rubber, with hole punches to make the stud holes. Finding a sheet of flat rubber may be difficult though..

 

Personally, I can't see why you couldn't use a silicon rubber "gasket" - One or two 3mm beads around the flange, allowed to dry/set and then bolted down onto would not be squeezed out - there are two types, one using acetic acid ( vinegar smelling) and one without - not sure which one would be the better for potable water applications but I don''t thing either silicon dissolves in water !

 

Nick

[Nickhlx]

Make up a (large) gasket out of rubber, with hole punches to make the stud holes. Finding a sheet of flat rubber may be difficult though..

 

Personally, I can't see why you couldn't use a silicon rubber "gasket" - One or two 3mm beads around the flange, allowed to dry/set and then bolted down onto would not be squeezed out - there are two types, one using acetic acid ( vinegar smelling) and one without - not sure which one would be the better for potable water applications but I don''t thing either silicon dissolves in water !

 

Nick

[alan_fincher]

Thanks Nick,

 

I must admit I did wonder about trying to make up some kind of "rubber" or neoprene type gasket.

 

The problem is the hatch is approaching 2 feet square, so to make it in one piece, with no joins, I'd need a very large piece of material. I haven't a clue where I might buy it.

 

I'm tempted to go the silicon route, despite what the surveyor said. It needs to be something that "sets" so it will not keep squashing out, when the hatch is walked on, but still has some spring and flexibility in once set.

 

Does anyone have any alternate suggestions please ?

 

There must be quite a few all steel integral tanks out there, on older boats, so I#m particularly interested to hear from anyone who has tackled the job recently.

 

Alan

[Ex- Member]

Neoprene strip could do it, when under pressure it will squease, when pressure released it will expand, a bit like memory foam. Some boat yards are now using Neoprene to fit hatches windows and portholes. Our weed hatch cover is also sealed with 2" neoprene strip.

 

Neoprene strip could do it, when under pressure it will squease, when pressure released it will expand, a bit like memory foam. Some boat yards are now using Neoprene to fit hatches windows and portholes. Our weed hatch cover is also sealed with 2" neoprene strip.

 

You posted just as i did. The neoprene strip can be butted tight together on corners or any join when squeased it will form a water tight seal. I've never had a single drip from the weed hatch. However water under pressure would be different. Also when tou remove the hatch in the future, if the neoprene is a bit naff you can replace it with new. It's not too expensive, you can get it up to 18mm thick in strips. Someone does it on e-bay you can order thickness length and the width you want.

[blackrose]

Marineflex. I use it for sealing the inspection hatch, bedding in skin fittings and it has hundreds of other uses on a boat. Really good stuff.

 

http://www.tradboats.com/conseamfillers.html

 

http://www.marinemastics.com/marine-flex/m...x-one-tube.html

[Ex- Member]

This is the e-bay shop selling neoprene strip.

 

Neoprene Rubber self-adhesive strip 50mm x 6mm x 10m

 

Item number: 250174570421

 

He only seems to have 6mm thick on sell at the moment, but 6mm would suffice. I did get some 8mm last time from him. I accidently typed 18mm in my last post, to confirm 8mm LOL

 

You can get it thicker from other outlets though, you can also buy it in sheet form.

[John Orentas]

There's nothing better than a good Silicone Sealant but make sure it prominently states RTV on the tube.. The force of people standing on the cover will be tiny compared to the force of the fixing bolts.

 

Replace the bolts with stainless steel A4 standard ones.

[DaveR]

Using stainless bolts with mild steel - doesn't that create galvanic reaction? Always been a bad thing in marine circles.

 

Dissimilar metals et al.

 

DaveR

[Speedwell]

Using stainless bolts with mild steel - doesn't that create galvanic reaction? Always been a bad thing in marine circles.

Dissimilar metals et al.

DaveR

This is true but it's better than rusted in bolts. I use stainless and smear them with silicone grease to reduce the corrosion.

I use sealer on mine. I use B & Q acrylic frame sealer, which is much easier to work than the silicone sealant as you can wipe off surplus with a wet cloth. It lasted the 4 years between tank paintings with no problem. When finished you can paint over the outside to match your deck paint.

Arthur

[floater]

How about foam tape. I'm thinking of using this for my windows

 

Click

[Ex- Member]

How about foam tape. I'm thinking of using this for my windows

 

Click

 

 

That's basically the same stuff as Neoprene Might not contain Neoprene though, sort of brand copy possibly, but does the same thing it seems.

[floater]

That's basically the same stuff as Neoprene Might not contain Neoprene though, sort of brand copy possibly, but does the same thing it seems.

At the bottom its got "Medium hardness multi-purpose foam seal, with similar properties to Neoprene"

Don't know if its better or worse than neoprene for these applications.

 

Phil mentioned sealing windows with foam tape in a previous post

http://www.canalworld.net/forums/index.php...dow++tape++seal

 

We use neoprene seals in air conditioning and they take 25 bar pressure when fitted between a recessed flange

Edited May 8, 2008 by floater

[Ex- Member]

At the bottom its got "Medium hardness multi-purpose foam seal, with similar properties to Neoprene"

Don't know if its better or worse than neoprene for these applications.

 

Phil mentioned sealing windows with foam tape in a previous post

http://www.canalworld.net/forums/index.php...dow++tape++seal

 

We use neoprene seals in air conditioning and they take 25 bar pressure when fitted between a recessed flange

 

Yeah Neoprene was developed 70 years ago mostly used for wet suits, but now has a multitude of uses. I've bought some from e-bay, chandleries, and ordered from here too.

 

http://www.sealsdirect.co.uk/bbCMS/shoppin...partmentId=1#15

 

It all looks exactly the same with the same colour brown protective strip, I'm pretty confident in saying it's all produced the same way. There are different densities shown in the above ling though.

[alan_fincher]

Thanks to all for many excellent suggestions.

 

Also to those who PMed me a response.

 

I'm spoilt for choice, and will now consider options.

 

John, I can't resist picking up on the old chestnut of RTV silicone.

 

After spending ages trying to buy some a couple of years back, someone pointed out it just means "Room Temperature Vulcanising" - i.e. it "goes off" at room temperature.

 

The reality is it's remarkably difficult to buy any that doesn't. I believe any Silicone you buy for normal domestic use is actually "RTV", even if it doesn't say so!

 

Alan

[blackrose]

On the subject of water tanks, there was a recent thread about painting tanks and someone mentioned tank liners in the form of a big bag which fits inside an integral tank so you never need to paint it. Or at least repaint it once, insert the liner and then forget it.

 

I can't find that thread now but does anyone know anything about these things and where to get one made?

[alan_fincher]

No,

 

But if they are any good, it would be bloody tempting!

 

I don't usually mind most boating jobs, however messy or uncomfortable. But this one takes the bidcuit for both uncomfortable & messy!

 

Currently the hatch is still open, in the vain hope that the stench of bitumen might die down.... Some hope, I think the first tankfull or two are going to be decidedly tainted!......

[Ex- Member]

No,

 

But if they are any good, it would be bloody tempting!

 

I don't usually mind most boating jobs, however messy or uncomfortable. But this one takes the bidcuit for both uncomfortable & messy!

 

Currently the hatch is still open, in the vain hope that the stench of bitumen might die down.... Some hope, I think the first tankfull or two are going to be decidedly tainted!......

 

I found these last week.

 

http://www.chandlery.net/groups/flexiblewatertanks.html

 

However I have seen basic butyl type ones in Black cheaper than these, that are roughly the size and shape of the bow water tank. Saw these fitted in a boat yard in Bristol, but can't find a reference to them on the net.

[Ex- Member]

I found these last week.

 

http://www.chandlery.net/groups/flexiblewatertanks.html

 

However I have seen basic butyl type ones in Black cheaper than these, that are roughly the size and shape of the bow water tank. Saw these fitted in a boat yard in Bristol, but can't find a reference to them on the net.

 

Possibly these, could be pricy though if have to be made to measure.

[LittleOuse]

We got ours lined with a non toxic polyurethane paint, sets like swimming pool liner, guaranteed 10 years. Lads cleaned it and painted it in two days at our mooring spot

http://watertankrelining.co.uk/wp/index.php/narrowboat-reline/

See before and after

[LittleOuse]

Going to use neoprene strip to seal, as recommended by our local Boatyard we bought 2.5cm wide and 3mm thick.

[ditchcrawler]

I use this for weed hatch sealing rather than just a strip with joints at each corner I just cover the underside of the lid WRONG LINK

Edited June 23, 2021 by ditchcrawler

[dmr]

49 minutes ago, ditchcrawler said:

I use this for weed hatch sealing rather than just a strip with joints at each corner I just cover the underside of the lid https://www.ebay.co.uk/itm/261237258709

 

That looks like solid neoprene rather than neoprene foam. Solid neoprene is quite hard, are you happy you got a good seal????

 

I used nasty black butyl rubber stuff but next time I will go for neoprene foam.

 

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

[matty40s]

1 hour ago, ditchcrawler said:

I use this for weed hatch sealing rather than just a strip with joints at each corner I just cover the underside of the lid https://www.ebay.co.uk/itm/261237258709

I wouldnt use that, the foam, once compressed does the job far better.

[ditchcrawler]

49 minutes ago, dmr said:

 

That looks like solid neoprene rather than neoprene foam. Solid neoprene is quite hard, are you happy you got a good seal????

 

I used nasty black butyl rubber stuff but next time I will go for neoprene foam.

 

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

No its a foam unless I posted the wrong link. I best go and check