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Old 11-12-2010, 01:14   #1
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New Water Tank - Stainless or GRP?

I just removed the port side (75 gal) water tank from my Morgan 416. Old polyethylene Tank came out largely intact (had to cut one upper corner off so it would fit thru hatch).

Question is: should I replace with a stainless steel fabricated tank or build a fiberglass one, using vinylester resin with an FDA approved catalyst to kick it off and building the glass tank over the old poly tank as a mold (with appropriate mold preparation).
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Old 12-12-2010, 10:16   #2
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why not replace with plastic?

i am removing a 30 year old mild steel water tank and considering the options too. from what i have read stainless steel can leak. fibreglass can break up over time too. seems to me that the modern plastic tanks are ideal. so why not plastic?
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Old 12-12-2010, 10:24   #3
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I would go with a poly tank. You can get them any shape or size.
PolyFab: Marine Waste Water Tanks
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Old 12-12-2010, 10:35   #4
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What prompted you to replace it?
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Old 12-12-2010, 11:52   #5
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Some of the newer cats are going to stainless steel as a safer option than either plastic or poly. I don't know if chemicals leach into the water from the poly but if you decide to use plastic I'd check to see if it is made with BPA.

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Old 12-12-2010, 12:04   #6
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Stainless suffers from external pinhead corrosion if they are constantly in salt water such as tanks in the bilge. Mine only lasted 4 years. They also can suffer internal pinhead corrosion which is what usually kills SS fuel tanks.

The fiberglass tanks on my current boat are still going strong after 40+ years.

I'd still think about plastic tanks if one is available. Would assume that would be the case since your previous tank was plastic.
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Old 21-12-2010, 22:02   #7
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If you can build a tank out of epoxy and glass and coat the inside with a food grade epoxy (to avoid the amine blush released by the epoxy curing process), the tank should last virtually indefinitely. I can give you the address of a good, commercial grade epoxy tank coating used for drinking water if interested.

Only problem would be from reverse osmosis, i.e water penetrating from the inside to the outisde of the tank. However with an epoxy tank and proper coating this should not be the case.

Building a tank out of glass is time consuming, however. Materials should be about half of what a new poly tank would cost but with those, welds are sometimes an issue and are not always an easy fix.
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Old 10-01-2011, 13:11   #8
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I can give you the address of a good, commercial grade epoxy tank coating used for drinking water if interested.
i would appreciate this info....
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Old 10-01-2011, 14:09   #9
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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
http://www.plastic-mart.com/class.php?cat=12
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Old 10-01-2011, 14:25   #10
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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.
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Old 10-01-2011, 14:49   #11
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What is Dave Gerr's reasoning? I still think polyethylene is the better technology for this application. It's also completely inert, you will never taste it.
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Old 10-01-2011, 18:26   #12
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Epoxy Coating

Hello

Are you still in West Palm Beach?

If so, Glue Products (I remember they were on Australian Ave) might still deal with food grade coatings.

I know they are still in business, we used to buy epoxy from them back in the late 80s...

Let me know if not, there is a good place in NC that we used about 5 years ago when we coated our tanks (with good success).

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Old 10-01-2011, 19:55   #13
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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.
And Nigel Calder says metal tanks should not be used for ANYTHING on a boat. I'll go with Nigel's opinion.
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Old 10-01-2011, 20:04   #14
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From a health point of view I would go stainless, We have poly tanks (with no BPA) however plastic leaches into your water (even if you cant taste it) the hotter the tank the more it leaches. Yes stainless has its draw backs (cost etc etc) however why risk cancer for a few hundred bucks...


I know this wont be a popular opinion (and it is just that) however health is a factor that's never really factored in.

Damien
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Old 13-01-2011, 12:38   #15
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The longevity of stainless steel tanks is in the proper installation.[/QUOTE]

I, too, am replacing a water tank. It's plastic with welded seams, is about 6 years old, and one of the seams is leaking. I'm told a seam cannot be rewelded with the tank in the boat. Since I'm removing it anyway, I'll probably replace it. Here's what I've found/concluded;

I now have a distrust of welded plastic seams (I realize the problem could have been improper installation, but.....)

Rotomolded tanks are available in many shpaes and sizes, but do not (cannot?) have baffles. I'm replacing a 70 gallon tank and having 500+ lbs of water sloshing around would seem to put a significant strain on even the best installation. Plus, there's the proper fit issue, unless it's custom made.

Assuming a dry bilge/mounting area, I'm starting to think stainless is the way to go. Now to my question. DeepFrz, you point out the importance of proper installation. Any idea where one would go to gain an understanding of what constitutes proper installation?
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