Fiberglass Water Tanks Crack Repair

[Rumi]

Hey Everybody,
I have a '94 Pacific Seacraft 34. Recently, the vent of the forward water tank was clogged causing the plastic lid to crack inward while the water pump was draining the tank. I found some surprises when I went into the forward water tank to clean it out. Some gooey mold had eaten its way through the tank creating a leak. There are also long thin cracks running down the vertical corners of the tank. The bottom and walls of the tank are fiberglassed as part of the boat hull and gel coated. I am wondering if anyone knows what product I could use to patch these cracks? I am a bit worried about poisoning the water with epoxy/coatings. Should I just hire someone to fabricate a plastic tank to fit into the space of the old one? See attached image of the tank.

[Nicholson58]

Ronco has a wide range of crazy tanks. Ratings are water or black water. You may need to ask for the special wonky shapes catalog.
https://ronco-plastics.com/product/w...-holding-tank/


Us Composite. Fiberglass , Epoxy , Composites, Carbon Fiber - U.S. Composites, Inc. Has a wide range of resins if you want to repair. They also can help you with the food grade questions, just ask.

[Chotu]

I’d fit a modern, poly tank in its place (inside it) and feel confident you have safe water to drink.

No matter how good you are with the epoxy mix ratio, you aren’t going to get it right molecule for molecule. There will be excess BPA or excess amine hardener. Those chemicals will be free to float off in the water and get inside your body (see near my username to the left about that).

Better to use more benign tank materials. Ronco, as mentioned above, is a good source.

[Flatswing]

Or u could just Clean it out Carefully & thoroughly. Grind out & repair cracks with CSM & Polyester laminating resin, refinish with gelcoat with wax, - no need to sand to Totally smooth gloss finish, good as new (replace the fittings of course).

[Stewie12]

I would go for a new poly tank.

[Dsanduril]

There are any number of epoxy coatings for the interior of potable water tanks. Grind out any cracks, fill with a structural epoxy, and then line the whole tank interior with an NSF 61 epoxy coating for potable water tanks. Note that the NSF standard only applies to larger tanks (more dilution for any contaminants from the coating) so look at coatings that say they are suited for smaller tanks, have 100% solids, etc.

[Saltyhog]

You want liqui-tile 1172.

[guyrj33]

Gooey mold? Could that have been oozing polyester blisters?

[Jono as 2234]

I had my black water tank custom made in poly. Probably cheaper than the off the shelf offerings and fit into a weird space. This was in Oz, but sure a Google search e would find a local manufacturer.
Jon

[Jammer]

Originally Posted by Rumi

Hey Everybody,
I have a '94 Pacific Seacraft 34.

Welcome

I am wondering if anyone knows what product I could use to patch these cracks? I am a bit worried about poisoning the water with epoxy/coatings. Should I just hire someone to fabricate a plastic tank to fit into the space of the old one? See attached image of the tank.

As far as I have been able to determine there are no fiberglass repair products currently on the market that are, according to their label, suitable for use on small potable water tanks. Such products existed in the past prior to the reduction in thec acceptable amount of BPA leaching into the water. Some are still available but have new labels indicating they are not suitable for tanks below a certain size, usually well into the hundreds of gallons.


You have four choices:


1) You can repair the tank with ordinary epoxy products perhaps with a topcoat that is designed for potable water use on larger tanks, if your assessment of the risks from BPA has determined that BPA is low risk.


2) You can replace the tank with a polyethylene or ABS one. Finding a tank of suitable size and shape may be problematic -- you will almost surely give up some capacity. A fact to consider is that these tanks also leach chemicals, though it's mostly molybdenum from the mold release compounds.


3) You can replace the tank with a bladder. This will give you the same, or possibly slightly more, usable capacity. Bladders pose their own chemical leaching problems


4) You can get someone to weld up a stainless steel one to match. Heavy and expensive but the fewest concerns with toxicity


Good luck

[Uncle Bob]

Hi, you say that the bottom and walls of the tank are fiberglassed as part of the boat hull and that the tank has cracks in the corners. Could these cracks be caused by the flexing of the hull? I would suggest that while you may repair the cracks they will probably return because of the normal hull flexing, so the only long term solution is in my opinion a new poly tank, either made to order or the nearest stock size and shape that will fit.

[windward1]

To expand on this thread; I have two integral fiberglass tanks where the tops leak. The boat is a 42 year old Cabo Rico. The tops are riveted on. I was planning on pulling the tops cleaning the seam and reattaching, or replace with a water bladder. At this point I cannot locate a bladder of the correct size; approximately 75 gallons each. Any thoughts would be welcome.

[Hoodsail]

Rumi, i have a similar fresh water tank the walls of which are fiberglass and part of the bow hull walls just as yours beneath my vee berth..thru the 8 inch inspection hole i have no cracks but the glass is shedding small bits and the tank that holds about 87 gallons has no baffles. Still debating what approach to take but found all of the following as sources of water quality compounds that i could paint onto the inner surface of my tank to seal it. The FDA regs, 21 CFR 17.105 and 171.300 provide detail. Compounds are; Ecopoxy, Mas Epoxies ($100/ 1/2gal), ceram-kote.com (ceram-kote 426) $145/gal, wolverine coatings.com (liquatile 1172 - UL water quality). Cant use: West system, 3M scotchkote 2400 or Tankguard from Jojun.com (only for concrete or steel tanks). Admittedly this information is about 1.5 yrs old...
Application requires the tank surface to be completely dry...and if a coating is applied, still havent solved the baffle issue...as I would rather not saw thru the top of the tank for more access to install. One option i saw was inserting "baffle balls" but my access port is too small a diameter....hoping to attack this project in Spring, 2021..

[Nicholson58]

More options:

these manufacturers list many rectangular tanks. Some Boat specific shaped tanks are available as well but you must ask. Ronco from Tank Depot made my holding tank, no two sides parallel. In my case, I used the drawings they furnished to select a likely fit and then made a cardboard mock up to verify.


PolyFab: Marine Waste Water Tanks | Acrylic Fabricators

https://www.plastic-mart.com/categor...ne-water-tanks

https://www.ntotank.com/duracast-marine-water-tanks

Start your replacement search here. These guys show drawings next to non-rectangular tanks. They will also add in fittings as you like and inspection ports. I bought from these guys, no problems, affordable.

Holding
https://www.tank-depot.com/p-158/ron...-holding-tanks
Water
https://www.tank-depot.com/p-157/ron...ne-water-tanks