Waterproofing a large underground tank

[jethro123]

Unusual question so any advice welcome.

I have an underground water storage tank of about 5500 gallons - its about 100 years old made from brick with a cement render over that. - Its very solid no loose render or cracks and generally in very good condition but it will not hold water very well , I am assuming it is seaping out through the walls. being 4 meters deep its under some pressure.

Any idea on the best approach to re-seal the tank from the inside only ? and thus has to be a relatively fume free solution.
Thanks

 

[noseall]

I have an underground water storage tank........Its very solid no loose render or cracks and generally in very good condition............but it will not hold water very well

A water storage tank that will not hold water!!!

Pity you could not install some kind of swimming pool liner to the inside.

If it is permanently empty then you are losing water low down.

 

[jethro123]

It appears to hold water only up to a couple of feet though it is constantly topped up when it rains always goes down again , no noticeable cracks as the walls are well rendered hence I believe its seaping through the walls.

Just wondering if a new coat of render with a water proof additive would do the trick ?

 

[Jasonb]

I've lined rendered blockwork ponds with fibreglass resin but you would need a reparator.

You could also try something like G4, this will seal sound render but if there are any fine cracks in teh corners or on the surface it won't fill them, again its quite volotile.

If its not for pottable water then maybe synfaproof, RIW or one of the Sika products will work

Jason

 

[jethro123]

Thanks Jason - I have thought of fiberglass and resin and would like to go down this route as it appears a more permanent solution. The thought of the fumes put me off but I could be more or less sure that its a lasting solution.

I would only need a thin coat as the background is so solid with perhaps a little thicker where the floor meets the walls and the floor itself - will look into a respirator

 

[Jasonb]

This site gives a good idea of whats involved and I've bought from them several times

Jason

 

[noseall]

The water seepage may be having a detrimental effect to the structure that causes a manifestation of problems, notably the wetter soil coupled with the added weight - plus wetting - plus weight etc.

Maybe you should let the whole thing dry out for a while and see what happens structurally.

Maybe i'm talking out of my rear 'cause i am not at all au fait with subterranean swimming pools but i would be concerned as to where the water is going.

 

[jethro123]

Hi Noseal - Its a 100 year old tank 5 meters deep down the garden , I have no doubt it seaping into the soil (chalk) but will take your advice and disconnect all the downpipes that feed it. I have drained it in the past for an inspection and with some strong lights checked that it is all sound Just for Info the whole area was an orchard and this was used as a water store.

 

[Nige F]

a little thicker where the floor meets the walls and the floor itself - will look into a respirator

see if you can get a fireman`s BA mask and an old compressor I did total cost £60 . the air pongs a bit but it`s only oil fumes not resin