cement water tank

[gdf26562]

Here I am in the middle of trying to do a renovation on my kitchen, and I find that my cement 5000 gallon water tank has sprung a leak, :mad:

The leak is at the top, just under the cap, (for want of better word), it appears to have a crack about 1metre long, only recently started leaking, at this stage just a small leak.

When I first moved in it had a leak, but appeared to seal itself, along some other cracks there appears to be a build up of a white substance, ?Lime???? I dunno, but it doesn't leak there now. Why is this so???

Also, the tank is covered by ivy, and looks great, but I think it may be aggravating the crack, by entering it, I have found Ivy to be very invasive, so I have cleared it away from the crack.

My question is, will the crack, when the water is lower, need sealing or should I leave it and hope it seals it's self, if in fact it does this.

Hoping it does, otherwise the kitchen will be put back a few months.

Any advice would be appreciated

[echnidna]

We have a similar problem at our scout camp. One of the committee bought some crystals at a recent field days that are supposed to seal up the leak. We probably wont get them in for about a month.
I dont have the contact details for the supplier yet but I have seen the crystals advertised in the Weekly Times classifieds.

[bitingmidge]

Don't know much about concrete tanks, but I've seen more than my fair share of leaking concrete buildings!

Firstly, the leak won't seal itself, so some work will be needed.

Do get rid of all plants growing on the tank, particularly ivy and others with active root systems. Even though you may not be able to see them, there will be microscopic cracks in the concrete, and in those cracks will be more moisture than elsewhere, and the nasty little roots will find them, make them bigger and you will have more visible cracks!

Don't be sold on any "fix" that involves putting anything on the outside. Having said that, and there are a number of "crystal" products which do work providing the crack is kept wet, which means in your case, you'll need a full tanks all the time.

Whatever the end fix turns out to be, and I know I am stating the obvious....make sure that it's suitable for potable water.

Hmm.....not much help I know, but at least you can get stuck into the plants till the solution comes along!

Cheers,

P

[journeyman Mick]

Not that it helps but the white stuff is called efflorescensce (sp?) It's a combination of minerals that builds up where water leaks through concrete. I guess it's acids and salts from the water leaching lime out of the concrete and depositing on the low pressure side of the leak. If, as you have observed, it tends to seal the leak up after a period of time it may do so again. The crystals that Echidna refers to are probably designed to aid in the sealing process. If this works- great! However in my experience few things are this easy or painless, problems rarely fix themselves. It may be neccessary to seal the inside of the crack with render or some proprietry repair product. Good luck,

Mick

[silentC]

You could try painting it with Silasec. I think it's OK for drinking water, in any case you can paint it on the outside.

[ozwinner]

Originally posted by echnidna
We have a similar problem at our scout camp. One of the committee bought some crystals at a recent field days that are supposed to seal up the leak. We probably wont get them in for about a month.
I dont have the contact details for the supplier yet but I have seen the crystals advertised in the Weekly Times classifieds.

I dont suppose you have a cow you would like to trade, I have these magic beans I'm looking at getting rid of?

Cheers, Jack

[davo453]

There are several products around for coating the inside of water tanks, they all need you to first drain the tank though. Another alternative is to buy a fitted liner but again you have to drain the tank first.

Draining occasionally is not a bad idea; the amount of crud that they can collect in only a few years is quite horrifying.

Cheers

Dave

[silentC]

If you use Silasec, you don't have to drain it, you can paint the outside. Would be better to do the inside though I think.

[journeyman Mick]

Darren,
I was trying to remember that name last night but I wasn't going to trek all the way down to the shed to find a bottle of it. You can make a thick "putty" using silasec and cement which would be perfect for this application.

Mick

[IanA]

There is a product called "Xypex" that is specifically designed for leak repairs in concrete. It works by promoting crystal growth in the crack

I first saw it used in the outlet tower of a water supply reservoir, so I assume it is considered safe with potable water.

It stopped the leak against a head of several metres. Really dramatic!!

A search on-line may turn up a current supplier.

[outback]

I have no experience of crystals, but like others they seem a bit of a magic fix to me.
From experience however, iif the leak is slow, and I mean weeping, not water actually running, chuck a handful of cement over it. I don't mean mixed up wet concrete but dry cement, straight from the bag. You may need to repeat the procedure a few times until it takes up.

The method is simple, quick and if it don't work you haven't wasted a heap of money.

I've used it afew times, and have been surprised at how big a leak you can stop.

[glenn k]

Its been a while since I had water tanks but I bought a place with 2 cracked 7000 gal tanks. I drained one into the other and painted the inside of the crack with a bitchemous paint sold for the purpose I had to do one twice put it worked. But these crystals sound better. I had a leak in my new 10000 gal tank and it to sealed its self.

[Robert WA]

I am with Glenn.

I remember back 50 odd years to my uncle repairing a squillion gallon stone and concrete water tank on the family farm with a bitumen product. He applied it inside the tank and it worked fine.

Chrystals worry me somewhat as the concept is that they form and expand in the crack. If they expand, do they make the crack worse?

A flexible, waterproof seal seems a better idea.

[silentC]

A QUICK SETTING PUTTY FOR SEALING AGAINST WATER BURSTS IN PIPES AND TANKS ETC.

(not my caps...)

http://www.bondcrete.com/Products/Wa...ec/Silasec.pdf

[bitingmidge]

As mentioned in an earlier post, crystal products do work (they cost a bit though) and they do require the water to be present at all times, although Xypex claims the crystals will "reactivate".

For more information Xypex

Or for those too lazy

To create its crystalline waterproofing effect, Xypex must become an integral part of the concrete mass. It does so by taking advantage of the natural and inherent characteristics of concrete; concrete is both porous (capillary tract system) and chemical in nature. By means of diffusion, the reactive chemicals in Xypex use water as a migrating medium to enter and travel through the capillary tracts in the concrete. This process precipitates a chemical reaction between Xypex, moisture and the natural chemical by-products of cement hydration (calcium hydroxide, mineral salts, mineral oxides and unhydrated and partially hydrated cement particles). The result is crystallization and, ultimately, a non-soluble crystalline structure that plugs the pores and capillary tracts of the concrete. In this condition, the pores become discontinuous and the concrete is thereby rendered impenetrable by water and other liquids from any direction. The Xypex crystalline process will reactivate whenever water is present.

Another product I have seen used successfully is Krystol

Oh how I hate leaking basements!
Cheers,

P