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Old 15-01-2011, 06:11   #16
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I would also like the name of a food grade epoxy paint for my GRP tank. I have done some repairs and need to coat fiberglass work...
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Old 15-01-2011, 08:18   #17
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In case anyone is interested, Dave Gerr states that stainless steel is the only material to use for water tanks.

The longevity of stainless steel tanks is in the proper installation.
The best installation of a steel tank I have seen was on my rib for the petrol tank. Stainless steel tank was rapped in a blanket of wet GRP and allowed to set. The whole lot was then glassed into the boat with support from the deck half way up the tank wall. Whilst GRP doesn't stick to S/S it didn't need to and since the tank couldn't move even a fraction, then the welds weren't stressed, another failure point for SS tanks.

The only problem I had was when I dropped a torch into the tank, but that's another saga.

It's the attention to detail in the installation of any type of tank that's important, just look at the weights that are involved especially in a violent sea way.

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Old 15-01-2011, 09:28   #18
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I replaced two stainless steel fresh water tanks that corroded out. I replaced them with polyethylene tanks. I thinks it's the best material for this application. The fiberglass tank you are considering could quite possibly cause your water to taste or smell like the resin you use.

Here is an idea of the cost. I can't imagine it being worthwhile to make your own unless the space is not a rectangular shape and you are trying to maximize the tank volume
Plastic-Mart - Rectangular Water & Waste Tanks :
Indeed!
Ronco Plastics - Marine Water Tanks, RV Water Tank, Auto Detail Tanks, Water Tanks
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Old 15-01-2011, 13:16   #19
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The best installation of a steel tank I have seen was on my rib for the petrol tank. Stainless steel tank was rapped in a blanket of wet GRP and allowed to set. The whole lot was then glassed into the boat with support from the deck half way up the tank wall. Whilst GRP doesn't stick to S/S it didn't need to and since the tank couldn't move even a fraction, then the welds weren't stressed, another failure point for SS tanks.
Actually, this is the worst possible thing you can do to any metal tank and is one of the reasons that metal tanks get a bad rep on boats. The tanks need to be mounted in a place where there is air surrounding them on something like HDPE. They need to be mounted so that they are not sitting in water and where any water that spills on them will drain away and allow the outer surface of the tanks to dry.

Encasing any metal tank in epoxy or fiber glass or spray foam will doom them to an early and ugly death.

Many steel fuel tanks rust out from water that leaks down from around the filler pipes bedded in the deck and then sits on the top of the tank.
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Old 15-01-2011, 17:35   #20
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When stainless steel is in an anaerobic environment it becomes active.

Higher grades take longer (such as Aquamet 22 and superaustentics) but they too will eventually succumb.
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Old 15-01-2011, 17:50   #21
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Tank coating epoxy

This is a FDA approved product for potable water and other human consumption liquids.

FDA rated epoxy paint and coatings product. For use on potable water tanks,brewing tanks, etc.

It is amine blush free, reasonably priced and lasts almost forever if properly applied. We prepped our tanks very well and applied 3 coats...

It also takes a while to cure fully...

Good luck, let us know how it goes!
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Old 07-04-2011, 12:46   #22
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Re: New Water Tank - Stainless or GRP ?

HDPE tanks are supposed to be BPA free. Check out the info on installation from Wrengco or Atlas tanks - firm floor and strapping seem to be their advice. Spreading the load makes sense for the hull too..
Having said that we have the luxury of gravity feed from a header tank to the galley - this is on the bridgedeck sole, well away from the salty stuff and therefore made of s/steel. Currently we're looking at either replacing or re-welding it as there are pinhole leaks around one of the baffle welds. Tank is about 30 years old though..
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Old 07-04-2011, 15:32   #23
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Re: New Water Tank - Stainless or GRP ?

I think a build in polyester / glass is also possible if gelcoat is used as the first layer. Molds - depending on what material is available at hand. It is easy to build over foam blocks if you can get the cheaply.


Otherwise polyethylene tanks are great and last well if you can find the shape you like. No taste either and they are food grade if made for water storage.

I would not use SS as they tend to corrode sooner or later. Our SS diesel tank is not in the bilge, good welding job and varnished too, and so what - it has rusty spots allover already.

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Old 07-04-2011, 15:53   #24
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Re: New Water Tank - Stainless or GRP ?

I'd go with a good quality thickwalled PE tank...and not worry about BHPs. Who do you know or ever heard of who's been made sick from a plastic tank?

Your profile gives your location as "out cruising," so I dunno whether a US supplier makes any sense for your...but Ronco Plastics Ronco Plastics (no relation to Ron Popeil and his VegoWonderStuff) makes TOP quality (about 50% thicker than any "off the shelf" or Kracor tanks) rotomolded PE tanks for a VERY reasonable price and has more than 400 shapes/sizes, including over 100 non-rectangular. And they install fittings in the sizes and locations specified by the client when they make the tank. Their prices are good enough that I think you'd have a hard time building one for enough less to be worth the effort.
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Old 07-04-2011, 16:18   #25
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Re: New Water Tank - Stainless or GRP ?

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Originally Posted by silverp40 View Post
When stainless steel is in an anaerobic environment it becomes active.

Higher grades take longer (such as Aquamet 22 and superaustentics) but they too will eventually succumb.
About tanks...
I vote with the food grade polyethelyne folks on water tanks. They're cheep, redily available, last a LONG time out of the sun, and are non toxic. Some other plastics are a very different story.

About Aquamet 22... My 7' drive shaft is made of it, and been submerged for 15 years now. It hasn't gotten a single pit, blemish, or spot of rust so far. This includes inside the two cutlass bearings, and 3' long stern tube as well. Maybe I've been lucky? M.
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Old 08-04-2011, 08:49   #26
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Re: New Water Tank - Stainless or GRP ?

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Originally Posted by peghall View Post
I'd go with a good quality thickwalled PE tank...and not worry about BHPs. Who do you know or ever heard of who's been made sick from a plastic tank?

Your profile gives your location as "out cruising," so I dunno whether a US supplier makes any sense for your...but Ronco Plastics Ronco Plastics (no relation to Ron Popeil and his VegoWonderStuff) makes TOP quality (about 50% thicker than any "off the shelf" or Kracor tanks) rotomolded PE tanks for a VERY reasonable price and has more than 400 shapes/sizes, including over 100 non-rectangular. And they install fittings in the sizes and locations specified by the client when they make the tank. Their prices are good enough that I think you'd have a hard time building one for enough less to be worth the effort.
Please correct me if I'm wrong, but judging by the Ronco catalogue, their rotomolded tanks do not have any baffles. Above a certain capacity, I think that's just a bad idea on a boat - too much weight sloshing around. Also, if the tank is a custom size/shape, rotomolding is very, very $$$$. I recently replace my failed welded seam plastic tank with a stainless tank. And, by the way, the stainless tank was LESS $ than the quotes I received for another plastic tank (custom size and shape). I guess I'll have to wait 5 to 20 years to see if it was a good move.
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Old 08-04-2011, 09:56   #27
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Re: New Water Tank - Stainless or GRP ?

Thanks all for the replies. I ended up using the old PE tank (minus a small portion of a corner at the widest spot so I could get it thru my hatchway - Morgan originally installed the tanks before the deck) to make a mold, then constructed a fiberglass tank using a vinlyester resin. The vinylester resin was FDA approved for food contact, but I wish I had used gelcoat for the first layer and then used epoxy for the rest. The water had a bit of a "plastic-y" taste/smell for a while (not our drinking water, which we run through a triple filter), but it has been better lately. We've been back on board full time for a month, so we're running quite a bit of water thru it. I'm happy with the GRP custom tank. Also, we built two baffles tabbed into the tank, and it turned out to be quite sturdy.

The project, however, took lots and lots and lots of time, and was more expensive than originally estimated by the guy that built it (with my assistance and grunt work). However, he capped his work, although at a higher amount than he originally said he cap it. I probably could've got a SS tank, built to match the old PE tank I removed, for less, and with much less time and hassle, but I suspect the GRP tank is a more permanent solution.

Dave
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