How to patch a leak our water tank?

lhyde · Post by **lhyde** » May 26th, '10, 20:22

I have a question about repairing a leak in the starboard berth water tank in Nutmeg, our CD 36. It is a plastic Kracor 46 gallon tank model 1-5141; serial # 84159. The tank has a 2 inch crack on the stern end just below a plug. It only leaks when the tank is more than half full. The crack extends into the threads of the plug. Can anyone recommend a product that could be used to patch the crack?
Thank you.
Les

Russell · Post by **Russell** » May 26th, '10, 20:29

Not much you can do to repair that type of plastic, epoxy wont stick to it. I fear a new tank is in your future, I know a lot of folks have replaced tanks and the manufacturer still makes them and has the specs for them on hand, so ordering an exact replacement sounds easy.

lhyde · Post by **lhyde** » May 26th, '10, 21:04

I was hoping to get through the year with this tank. I was thinking of trying to force a product into the crack... maybe silicone caulk, 3M 5200, or ????

Oswego John · Post by **Oswego John** » May 26th, '10, 21:41

Before you go ripping your tank out, I'll mention something that you could try first. It's called 3M Scotchcote.

This stuff is dynamite. It's used on high voltage splices, buried electrical installations, moist locations and it is in wide use on nuclear installations. I don't know much about different kinds of plastic. This stuff seemed to adhere tenaciously on everything I put it on. It is excellent for bonding, too.

Many years ago I had a Mini-Cooper with a fuel pump atop the gas tank. (petrol?

). It had a split in the plastic body and sprayed gas all over the place. I tried everywhere to find a replacement. The only one I could find was a used one for somewhere between $350.00 and $400.00. I couldn't swing that. I glommed a can of Scotchcote from work and put it on the split in the plastic body. I never had a problem with it since.

http://www.shop3m.com/scotchkote-electr ... ating.html

The ad shows a 16 oz. can. You wouldn't use 16 oz in 16 years. It come in smaller cans at much less $$$. Any electrical supply will carry it. Also some big box stores,

Also click on the spray can of 96% pure zinc. 3M is top shelf.

Good luck,
O J

Russell · Post by **Russell** » May 27th, '10, 01:26

If your not drinking the water in the tank, try whatever you can. But if you are drinking it keep in mind many of the possabilities are NOT for potable water.

Kevin Kaldenbach · Post by **Kevin Kaldenbach** » May 27th, '10, 06:52

I used a soldering iron and a "small" torch to fix the gas tank on my outboard. I shaved some plastic off of a seam on the tank to melt in as a filler. I would try to use the same plastic to melt into the repair, if you need filler.

lhyde · Post by **lhyde** » May 27th, '10, 07:19

As this is our drinking waer I am concerned about chemical contamination, although the "fix" is on the outside of the tank. I might try the melting idea and will look into the label on the scotchcote. Thanks for your suggestions.
Les

Greg Kozlowski · Post by **Greg Kozlowski** » May 27th, '10, 07:30

Hi Les,

The polyethelene water tanks on our 1979 CD36 had serious cracks which I was able to repair with polyetheline sticks or more commonly known as candles. I got mine at a hardware store, but they may also be available at ski repair shops. I used a soldering gun to heat the crack and melt the stick into the void. It has held up well for the past ten years.

If polyetheline is what you mean by plastic, then I highly recommend trying this repair.

Greg

Jim Evans · Post by **Jim Evans** » May 27th, '10, 08:03

I recently discovered leaks from the stbd water tank on my '81 CD33 - it's also a Kracor tank. The leaks were from cracked fittings at the top of the tank. Some research revealed that 3M Adhesive DP8005 is the only adhesive that will work on our polyethelyne tanks. You can get the adhesive at Jamestown Distributors, though the combination of the adhesive, mixing nozzles, plunger and applicator will cost about $110. I bit the bullet and bought all the stuff, and it works great. It's cheaper than a new tank. You can check it out at http://www.jamestowndistributors.com/us ... 5_adhesive

I've not tried Greg's suggestion of the "candle" with the soldering iron.

sharkbait · Post by **sharkbait** » May 27th, '10, 08:30

You can actually weld the crack. There are heat guns available that have a very small highly concentrated output. You can also buy different type of "plastic" welding rods.

Look for the tools and materials under welding supplies.

craig · Post by **craig** » May 27th, '10, 11:17

we fixed several leaks in the original water tank in our cd 27 while in florida this winter. both the vent fitting and outlet fitting leaked as well as a crack in the side of the tank.
we bought a plastic fitting at ace which threads together and has female threads on both sides. they are used on plastic agricultural tanks and washing machines. it is a two part fitting with a large flange and a rubber gasket.
we used aquarium silicone which is also available at ace and is rated food grade.
the next step involves installing an inspection port large enough to fit your hand in. these are available from wm, defender and others. cut the hole in the top of your tank close enough to be able to reach the repair area. the cut out from the inspection plate will serve as your repair piece.
cut off the leaking fitting and use a hole saw to drill it out. the hole should be slightly larger than the threaded body of the new fitting. now drill a hole in the material removed from the lid of the tank. cut it if necessary to fit in the corner of your tank. you will be sandwiching this piece on the inside of the tank between the two parts of your repair fitting. use lots of silicone between the tank side and your repair piece.
assemble and make sure you have a nice squeeze out of silicone. dont be tempted to over tighten. allow to set up one day. i know silicone is not a super adhesive but it makes a great gasket. finally you can install
threaded plastic pipe fittings into your repair fitting and re-attach. when drilling out the old fitting you may need to make a temporary plug to center your hole saw. use a hole saw big enough to get rid of the old fitting. cutting boards sold at ace and elsewhere(the white ones) are the same material as our holding tanks and make great repair material also.
call me or email for any other info.

craig · Post by **craig** » May 27th, '10, 11:22

i forgot to add that if you don't need to make the repair at a fitting location you can simply plug both sides of the repair fitting with an appropriate threaded plug. use the same silicone on the threads.

lhyde · Post by **lhyde** » Jun 2nd, '10, 16:25

Thank you for all the suggestions on repair of the water tank. After making a couple of phone calls I found that a local shop, Lyman-Morse in Thomaston, ME, does plastic welding. I hauled it up there and they patched it for a modest price.

I so appreciate all your help.

Les

M. R. Bober · Post by **M. R. Bober** » Jun 4th, '10, 15:28

Kevin Kaldenbach wrote:I used a soldering iron and a "small" torch to fix the gas tank on my outboard. I shaved some plastic off of a seam on the tank to melt in as a filler. I would try to use the same plastic to melt into the repair, if you need filler.

Kevin,
I think I saw your movie, "Death Wish". Open flames and an "empty" gasoline tank...hey what could go wrong?

Mitchell Bober
Sunny Lancaster (where we don't need no stinkin' safety officer),VA

Jeff and Sarah · Post by **Jeff and Sarah** » Jun 16th, '10, 12:55

I'm sitting outside a plastic welder's shop stealing someone's wireless internet signal and thought I might provide a word of caution regarding the polyethylene water tanks (at least those on 33's and 36's). I suspected that I might have a leak in my starboard tank and after pulling the tank out and filling it on the dock I saw a very thin crack that was dripping. The crack was located inside the recessed portion near the centerline on the bottom of the tank. That made me worry about the port tank so I pulled that one too. No cracks, but one of the spare fittings that should be capped was completely broken off, leaving about a 3/4 inch hole where the fitting and cap should have been. Back to the starboard tank to check the spare fittings on that one and sure enough, one of the capped fittings had a major crack in the plastic weld.

I found a local plastic welder and am having the crack repaired along with the two smaller spare fittings on both tanks (so 4 total) completely removed and patched to prevent future cracking. If you're looking for something to on your boat over a beer, try pulling up the settees and checking your tank fittings before you find yourself low on potable water while the bilge pump drains your batteries.

Jeff

The Cape Dory Board

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