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Old 25-07-2015, 19:33   #16
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Re: Leaking fitting on polyethylene holding tank

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Originally Posted by exMaggieDrum View Post
The Uniseal that Peg posted about looks great but I suspect that it is only suitable if the area around the hole is the same circumference as the largest part of the Uniseal flange.
Apparently you failed to notice how many sizes the Uniseal offers. Worst case, you might have to a bigger one than the fitting you're replacing...a reducing adapter solves that problem....or if it's waste tank vent, a larger vent line. Tank mfrs are using Uniseals...for example Dometic (formerly known as SeaLand Technology) uses them in their kit that moves tank discharge fittings to the top of the tank with a pickup tube inside the tank. At least one tank mfr--Trionic--offers them too.

If you opt to try heat welding instead, you'll need to melt both the new material and the edges of the hole you're trying to fill, so that they become one mass. If you only add meltedg new material, the patch will only fill the hole, it won't bond with it.
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Old 26-07-2015, 03:04   #17
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Re: Leaking fitting on polyethylene holding tank

a good soldering iron and a milk jug will solder it for you. work slow so they melt together..
ted
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Old 26-07-2015, 08:48   #18
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Re: Leaking fitting on polyethylene holding tank

There is a 2 part PTFE glue available that I have used on a water tank. It requires heat treating the repair area but this is easy but u need a blow torch.

Mechanical repairs are fine...only if the location is flat...
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Old 26-07-2015, 09:36   #19
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Re: Leaking fitting on polyethylene holding tank

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Originally Posted by peghall View Post
Apparently you failed to notice how many sizes the Uniseal offers. Worst case, you might have to a bigger one than the fitting you're replacing...a reducing adapter solves that problem....or if it's waste tank vent, a larger vent line. Tank mfrs are using Uniseals...for example Dometic (formerly known as SeaLand Technology) uses them in their kit that moves tank discharge fittings to the top of the tank with a pickup tube inside the tank. At least one tank mfr--Trionic--offers them too.

If you opt to try heat welding instead, you'll need to melt both the new material and the edges of the hole you're trying to fill, so that they become one mass. If you only add meltedg new material, the patch will only fill the hole, it won't bond with it.
Hi Peg - I did note the range of sizes from Uniseal. My comment only applies when the weld is literally at the edge of one side to the top, or another side, where there would be literally no space on that side of the weld for a seal to seat on. That was the situation on my tank.
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Old 26-07-2015, 20:58   #20
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Re: Leaking fitting on polyethylene holding tank

OK now this is my field, a fitting on a (PE) polyethylene tank fitting is usually a spin welded fitting or hot gas welded (depending on what fitting is broke) it is best if you can find someone that has experience in hot gas welding and has 1/8 or 3/16" PE rod, make sure that it is not HDPE and that a test weld is done on a area outside the cracked area, the rod should be welded to the tank with about a 6" tail, let the weld totally cool then grab the tail and pull the tail, if you have a good weld the rod will stretch close to the weld until it breaks the rod, the weld at the tank should remain intact. As far as using a soldering iron or the like is called a tack weld for joining 2 like plastics together but will NOT produce a structural weld. there are many adhesives out there (I like GOOP combined with a fiberglass cloth) this is a stopgap until you could get the tank welded. I have not in 35 years of working with plastics found a adhesive that will bond two pieces of PE plastic together, you can always get under it and pull it off or use a solvent to soften it. I hope this helps.
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Old 06-01-2016, 13:06   #21
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Re: Leaking fitting on polyethylene holding tank

Peg,

I read with interest your post regarding the Uniseal Products. Do you think that such a fix would work with a broken female vent fitting on a water tank">fresh water tank? That's the problem I have.

Are the uniseals threaded? On my tanks, both the male hose and the female fitting (which attaches to the tank) are threaded.

I believe the tank is polyethylene, but I suppose it could also be polypropylene.

I have also attached some pics. to show what I am facing.

Thanks in advance for any ideas or assistance you may be able to offer.
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Old 06-01-2016, 14:23   #22
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Re: Leaking fitting on polyethylene holding tank

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The "weld" connecting the male threaded outlet on my holding tank has developed a significant leak. Is there a way to repair/reweld this fitting without having to pull the tank out of the boat?
Can you reach into the tank? If so I would use a through hull. Probably a lot better than messing with trying to weld plastic.
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Old 06-01-2016, 17:39   #23
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Re: Leaking fitting on polyethylene holding tank

Thank you for your reply.

Peg was writing about a leak-proof fix that does not require a weld.

She wrote of a Uniseal product that press seal fittings.
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Old 06-01-2016, 18:40   #24
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Re: Leaking fitting on polyethylene holding tank

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Thank you for your reply. Peg was writing about a leak-proof fix that does not require a weld. She wrote of a Uniseal product that press seal fittings.
Not quite. The Uniseal can't repair a leaking fitting, but it's the best way I've found to relocate or add a fitting. UNISEAL
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Old 06-01-2016, 18:50   #25
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Re: Leaking fitting on polyethylene holding tank

Thank you for your reply Peg.

If I plugged the current vent-hole, and drilled another hole nearby, would Uniseal be the right product for my purposes?
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Old 06-01-2016, 22:10   #26
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Re: Leaking fitting on polyethylene holding tank

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Thank you for your reply Peg. If I plugged the current vent-hole, and drilled another hole nearby, would Uniseal be the right product for my purposes?
Yes. Use a threaded plug wrapped in Teflon tape to ensure a good seal in the "old" fitting.
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Old 07-01-2016, 03:01   #27
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Re: Leaking fitting on polyethylene holding tank

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Yes. Use a threaded plug wrapped in Teflon tape to ensure a good seal in the "old" fitting.
The original vent hole in the tank has no threads. The female connector, which is threaded, must have originally been welded to the outside of the tank. Yet, the actual vent hole is unthreaded.

Can that original vent hole be tapped with threads?

If not, wouldn't a cork suffice to plug the old vent hole?
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Old 07-01-2016, 05:52   #28
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Re: Leaking fitting on polyethylene holding tank

There is another way!!!

I had a similar problem on the fill fitting for my water tank. One can heat weld spin fitting's, if you are careful.

This is what I did - first to preserve the roundness of th PE female fitting, thread a PVC male fitting into it. Since PVC has a higher melting point it will stay solid when th PE welds. I used a male plug to minimize the weight. A bushing would also work. I then heat welded a new spin weld fitting to th tank. This process should also work to repair a leaking spin wild fitting. You will need some PE to fill the annular space. NOTE APPROPRIATE PPE SHOULD BE USED.

When I was done the threads were a little "sloppy" so when I put everything back together again, I wrapped the threads with some tape.

You should also determine why the weld cracked. Is the weight of the hose pulling on the fitting?
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Old 07-01-2016, 06:37   #29
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Re: Leaking fitting on polyethylene holding tank

Marinetex RM321K FLEX SET 30G EPOXY ADHESIVE



This stuff is magic.
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Old 07-01-2016, 08:44   #30
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Re: Leaking fitting on polyethylene holding tank

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Originally Posted by poshman View Post
Peg,

I read with interest your post regarding the Uniseal Products. Do you think that such a fix would work with a broken female vent fitting on a fresh water tank? That's the problem I have.

Are the uniseals threaded? On my tanks, both the male hose and the female fitting (which attaches to the tank) are threaded.

I believe the tank is polyethylene, but I suppose it could also be polypropylene.

I have also attached some pics. to show what I am facing.

Thanks in advance for any ideas or assistance you may be able to offer.
Here is a site with pictures of various seals that can be used on tanks:

Bulkhead Fittings & Adapters Category | Bulkhead Fitting, PVC Bulkhead Fittings and Bulkhead Adapters. | U.S. Plastic Corp.

I used a bulkhead fitting for mine since my existing fitting was at the top of the tank - as your is. A bulkhead fitting requires putting a threaded backing plate on the inside which is then tightened with the outside fitting. The inside, female, of my fitting was threaded as well so I could attach my hose with a male threaded pipe (like yours). It is a very secure fitting and seals well when prepped well and tightened up well. I put my new fitting on the top of the holding tank so it would be less likely to fill with overflow when the boat is heeled over. That is not critical for a fresh water tank.

Uniseals are a "pressure" fit which requires the un-threaded pipe to be pushed in as a very tight fit. The pressure on the female of the seal then presses on the tank material and makes the seal. The pipe from the tank is not secured so it would have to be well secured to not move after installation, as close to the seal as possible, so it cannot move. This could put uneven pressure on the seal and let it leak from the looser side. It does not require an inside plate so the interior clearance is not an issue. The hole does have to be reasonably smooth and must be 100% round and the right size for the seal. The pipe must be the right size for the seal as well.

If it were me I would put in a bulkhead fitting and plug the old hole with a male pipe plug (if the threads are good and no cracks around the existing fitting). If you have cracks then you will need to repair those in any case or enlarge the hole for a uniseal (which looks to be difficult to do). It is possible, but very difficult, to drill a bigger hole to take out the cracks and get to good material and put in a uniseal but you probably don't have room on the top side for that.

Hope this makes some sense. I can't comment on the welding repair that was previously discussed.
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