# Forum Home Renovation Water Saving Garden Ideas  Concrete rain water tank pop out of ground

## voodoo

My 30,000 litre concrete rain water tank which was more than half burried in ground just raised out of ground one day by about one foot ripping off all the plumbing and electrical lines...........No one has any idea how it happened and whose fault is it......builder's, installers, or God's....(just kidding)....and who's gonna pay for it?????
Can any body give me any expert advice or contact of any expert (in logan, QLD) who can inspect it and tell me why it happened and what needs to be done to prevent it and most improtantly who should bear the cost of repairs????
thanks
voodoo

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## president_ltd

> My 30,000 litre concrete rain water tank which was more than half burried in ground just raised out of ground one day by about one foot ripping off all the plumbing and electrical lines...........No one has any idea how it happened and whose fault is it......builder's, installers, or God's....(just kidding)....and who's gonna pay for it?????
> Can any body give me any expert advice or contact of any expert (in logan, QLD) who can inspect it and tell me why it happened and what needs to be done to prevent it and most improtantly who should bear the cost of repairs????
> thanks
> voodoo

  hydrostatic pressure is an awesome thing.  its why pools have a hydrostatic relief valve in the bottom.  why or how it happened isn't really rocket science.  concrete can float. see Concrete ship - Wikipedia, the free encyclopedia 
as to who is at fault - hard to say.  who chose to bury the tank?  what height is the water table at?  what drainage do you have?  did anyone specify what mechanism would be provided to relieve any built up water under the concrete?

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## voodoo

we bought the house as a house and land package directly from the builder with the tank already in place..............dont know any technical details about that tank..........now when we contacted the builder he is saying that he got some other third party to install the tank...so why should he pay for what he didnt did himself?
The tank is to have one third water in it at all time, which is supposed to be enough to anchor it in place........that water is there........but the tank still raised....installation fault or act of God?

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## SilentButDeadly

Installation fault.  It should have also been restrained by four ground anchors (wire ties to horizontal gal bars buried at the same depth as the bottom of the tank). Pressure relief could also have been provided by a 50mm pvc pipe vertically alongside the tank to a spider of slotted agg drain underneath the tank.

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## voodoo

thanks.......I hope armed with this knowledge i'll be able to tackle the builder :Smilie:

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## intertd6

something is not adding up here, 1/2 tank buried = 15 tonnes up lift - 10 tonnes of water - weight of tank ( say 5m3 of concrete @ 2.4tonnes /m3) = 12 tonnes = 7 tonnes of downforce. I'd be saying someone has lowered the footvalve to get more water out of the tank during this dry time & when it rained its floated.
regards inter

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