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Rainwater tank - how to fix leaking bung?

G'day

A small leak has started from low bung in 5000l water tank, new house, tank is approx 5 years old. In photo you will see that the bung was maybe over tightened on install (see o-ring that has bunched up near top). I suspect the bung may have been knocked by one of the kids parking a bike & this was just enough to start a slow drip leak.

Question is - can I just tweak this a little tighter with a wrench? or, any other more sensible solution?

PS: Tank is full.

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Comments

MitchellMc

Welcome to the Bunnings Workshop community @Garvo. It's fantastic to have you join us and many thanks for your question.

You might be correct that the fitting was over-tightened in the first place, or perhaps it has been tightened already to stop a slow leak. The rubber o-ring appears rather pinched, and tightening the fitting further is likely to make the drip worse.

It would be best to look at either replacing the o-ring or backing the fitting out far enough to add thread tape instead. I would imagine the current o-ring is crimped and set into that shape, and you won't be able to use it.

Let me mention @TedBear, and @r23on see if they would like to join the conversation.

Please let me know if you need further assistance or had questions.

Mitchell

Garvo

https://www.workshop.bunnings.com.au/discussion/comment/11993#Comment_11993

Thanks Mitchell - appreciate the advice. I'll wait to see if your mates have anything further to add, otherwise, I'll proceed with the backout & thread tape attempt at fix - any idea on how long that thread on the bung might be?

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/68422#Comment_68422

It's a bit hard to tell as there is no generic length @Garvo. I'd hazard a guess that you should be all right backing it out until you see a centimetre of an exposed thread. Any further and you'll risk it coming out completely. Overall, it might have 20mm of thread.

Mitchell

TedBear

https://www.workshop.bunnings.com.au/discussion/comment/68422#Comment_68422

I think Mitchell's approach sounds good. Maybe have a large rubber ring seal handy too, which you may be able to stretch over the bung, in case that existing seal comes apart when you back the bung out. Optionally, can the bung be replaced with a tap?

I replaced my tank tap last year... a bit messy, but I found that by attaching a long hose to the new one first & having the tap open (so ur not fighting against water pressure & the outflow isn't all over you), I was able to get old one out and new one in quickly & with very little water loss. (A minimal drowning.)

Garvo

https://www.workshop.bunnings.com.au/discussion/comment/97125#Comment_97125

Thanks TedBear - good idea RE: having a large seal on hand to see if I can stretch it over. The tanks are already plumbed to garden taps, internal water to toilets etc - so probably won't go the tap route, but I get what you're saying regards using the hose/tap to manage the pressure for install & may visit this if I can't get the bung to seal.

TedBear

https://www.workshop.bunnings.com.au/discussion/comment/115196#Comment_115196

Best of luck. Keep the wellies handy just in case 🙂.

redracer01

Hello @Garvo

If you say that the bung has been knocked off the threads or a small hairline crack has occurred somewhere near the bung then I suggest the following. If the tank is full it will be difficult to repair and we can only patch it from the point of the leak, I suggest kneadit Aqua :

A hand kneadable, fast-setting co-extruded epoxy repair system. Ideal for repairing generators, water and fuel pumps, it is easy to use, doesn’t sag, run or drip, and hardens within 20-30 minutes. It can be drilled, sawed, sanded, filed, tapped, machined or painted one hour after mixing. *Pre-test required on plastics before use. You may have to wrap it tight around the leaking area with some temporary tape to keep the knead it from being pushed off by the static pressure of the water. But once it hardens you can take the tape off.

I've seen it used on fiberglass and aluminum boats, esky's and bait boxes. The best part it works underwater so even if it immersed in water it will still seal the leak. You can also try Rust-Oleum 25.4mm x 3.04m Black LeakSeal Self-Fusing Silicone Tape. This tape once applied must be pulled and stretched to activate and must be wrapped overlapping to give a proper seal. Once it goes off it hardens like rock and the seal is permanent. But if the tank is fairly low then I would try all the other suggestions the guys have made and see which one works best. My solution only applies if the tank is full and opening it will cause a great deal of water to be wasted. Good luck and stay safe.

Cheers,

Red

Screenshot_2021-02-02 Rust-Oleum 25 4mm x 3 04m Black LeakSeal Self-Fusing Silicone Tape.png Screenshot_2021-02-02 Selleys 50g Aqua Epoxy Putty Knead It.png

Garvo

https://www.workshop.bunnings.com.au/discussion/comment/12003#Comment_12003

Thanks Red for the sealing suggestions. Tanks are full so appreciate the product recommendations.

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