Leaking plastic freshwater tank at drain

[gonesail]

G-Flex epoxy by West Systems is advertised to seal plastic tanks. as the OP said: flame treatment on the area enhances the bonding.

[TedeBoy]

Originally Posted by peghall

Don't do anything until I hear back from Loctite...their contact form said to expect a reply within 72 hours, so it may be a couple of days.



Meanwhile...heat welding requires a tool that can melt both sides of the crack while it injects new material. That's prob'ly gonna screw up the threads. If there's a plastics fabricator in you area, you might want to give them a call to find out what you can do to salvage it. If there is one, and IF you can remove the tank, it's a simple matter for them to remove the cracked fitting and spinweld a new one into the tank.


I'll get back to y'all as soon as I know more.


--Peggie

I called Loctite. The 3530 bonds to polyethylene.
They also suggested MR 5438 thread locker as a non glued option.

Here my concerns.
If I glue a fitting in then there is no going back should it not seal.
I want to try all non glued in options first.
The tank cannot be removed. Far too costly. I need to get this right.
I'm next going to reinstall the hose clamp around the female tank fitting to minimize or halt the crack separation as the NPT is tightened. I'll be real gentle and goop both threads up with the 5438 as I slowly tighten it snug. I'll let it cure and test.

[Cheechako]

You need a clean out port in the top of the tank anyway. Put one in. There are many screw in round ports available cheap with oring seal.
Then hole saw the bad fitting out and install a mushroom thru hull fitting or similar.
We're not talking an expensive parts list ($35?) and it's a permanent fix not relying on "does that glue hole in situations where there is water in the crack?"

[TedeBoy]

Originally Posted by Cheechako

You need a clean out port in the top of the tank anyway. Put one in. There are many screw in round ports available cheap with oring seal.
Then hole saw the bad fitting out and install a mushroom thru hull fitting or similar.
We're not talking an expensive parts list ($35?) and it's a permanent fix not relying on "does that glue hole in situations where there is water in the crack?"

The tank is not accessible.
It's under the sink.
I'll look for a way to cut cabinetry but I doubt it.

[peghall]

That sounds like a pretty small tank. Can we find a new location for a new larger tank and just eliminate that one?


--Peggie

[TedeBoy]

Originally Posted by peghall

That sounds like a pretty small tank. Can we find a new location for a new larger tank and just eliminate that one?


--Peggie

It's a 50 gallon tank.

[peghall]

Didn't expect a tank "under the sink" to be anywhere near that size! But that may or may not rule out finding another more accessible location for a new tank and scrapping this one. Ronco Plastics Ronco Plastics marine Tanks makes TOP quality thick-walled water and waste tanks for a very reasonable price and have more than 400 shapes and sizes, over 100 of which are non-rectangular, and they install fittings in the sizes and locations specified by the customer when they make the tank. Worth considering anyway. Their drawings can be oriented any direction 'cuz there is no top or bottom till the fittings go in, and you decide where they'll go. So rotate 'em, flip 'em...it's rare not to find a tank that's close the size of a tank being replaced.



--Peggie

[Simi 60]

Originally Posted by peghall

.fittings must be installed using a process called "spin welding" that melts the edge of the fitting and the edge of the hole it's going into so that they run together to become a continuous mass..



--Peggie

Back to my childhood

Got a string controlled plane for xmas but never got to fly it.
Bloody thing melted when left in the back seat of dads car a couple of days later.

https://m.youtube.com/watch?v=PnWpcwnR2YA

[Bill Creadon]

I have worked in the plastics field for 40 years and own a plastic fabrication company. The tank is a roto-molded polyethylene material that is 24 years old and beyond it's plastic life. Water tanks are subjected to chlorine and chemically attack the PE over time. We hot air weld and fit fittings on new tanks. We have tried to fix tanks and fittings younger than this with limited success.
First, the fitting was injection molded and then roto-molded into the tank. The injection molded fitting is cracked at the area where the 2 mold halves come together, called the parting line. The material knits at this line in the molding process and will be the weakest part of the fitting. This is your failure point. If you apply any adhesive it may work for awhile, but it will eventually fail. You have got to remove the tank and replace it. It probably means cutting some cabinets or bulkheads. When you get the tank out look for the manufacturer's name. If you try Ronco or other suppliers and can't find it take the old tank to a plastic fabricator and have him duplicate it from sheet material and new fittings. Just remember PE is a polyolifin and doesn't accept adhesives. If you decide to use something use a tube product that is like a white liquid Teflon that is used on plumbing fittings. Make sure it is clean and take a torch and kiss the outside surface of the thread for better adhesion before using the sealant. Only a temporary fix. Over time it will break down. Good luck with this problem.

[keepondancin]

Is it possible to use a Fein tool and cut out a bit more of the flooring, cat an access into the bottom of the tank and stuff a bladder in the tank? I guess motor home builders and boat builders think alike. People that design and build these things should also have to fix them. Things would be different.

[TedeBoy]

UPDATE

I was able to install a flex coupling around the cracked tank fitting.

It is holding so far!

More tests today including full tank and driving.