Watertight coating or membrane? (must be food safe)

[DaveReading]

We have a fairly elderly water softener, still working well and making a world of difference to our previous limescale problems.

Unfortunately, a few years ago and for reasons I can't remember, I filled it with water while it was resting on a couple of bricks and the weight of the water caused a hairline crack in the bottom of the outer shell. It now suffers from a minuscule leak - there's not normally any water evident, just dried salt on the outside as the small amount of leaking brine evaporates.

It now sits in a seed tray to stop the floor tiles being contaminated, and every few months I wipe away any salt deposits, but I'd like a more elegant solution (npi) to the hairline crack leak.

I'm thinking in terms of either some kind of membrane or waterproof coating that I can apply to the bottom of the shell, inside, to make it watertight once more. It would need to be food safe (alhough we don't actually drink softened water) and not be affected by the brine.

Any suggestions? Thanks in advance.

 

[Cycleops]

What material is the outer shell?

 

[DaveReading]

It's plastic - fairly rigid, but I couldn't swear as to what particular type. About 4 mm thick.

 

[classic33]

Plastic liner, cut to accommodate any fittings that are attached.

 

[bruce1530]

You can get food-grade silicone sealants. Maybe something like Dow-Corning 781 - from Screwfix etc. Says it’s safe for contact with drinking water.


https://www.screwfix.com/p/dow-781-...ml/45959#product_additional_details_container

 

[slowmotion]

I would roughen the outside surface with abrasive paper, mix up polyester resin and a tiny amount of catalyst, and brush it over the crack before pressing in a narrow glassfibre tape and adding more resin mix. If the cured resin adheres to the plastic, it won't leak. I've fixed our incoming mains pressure water supply pipe similarly and it lasted for years and years before the water company replaced the old lead pipe with a new plastic one.

 

[DaveReading]

Some interesting suggestions, thanks.

I'm torn between the idea of the impervious liner, in the form of a deep tray made from folded polythene or something similar, and the sealant approach. Re the latter, while I'm not entirely sure where on the bottom the hairline crack(s) are, a standard tube of sealant would be enough to cover the entire base (inside or out) to a depth of 2-3 mm.

The fibreglass/resin approach sounds interesting too, though in my case there's very little pressure involved - the brine chamber is open to the atmosphere, so it's only the weight of 2-3 inches of brine that needs to be contained.

Thanks again, chaps.