# Forum Home Renovation Pools, Spa & Water Features  Help - my pool is growing stalagmites

## Wombat2

My 16yo concrete inground pool - (12.5m x 4m) lined with pebblecrete is starting to send up bumps from the bottom. Started with one about 12 months ago and now there are several. First the pebbles come off and leave white steaks then the mound starts to grow - the original one is about 1 inch high. The others are below 1/2 and inch to zero depending on the age.  All reading with the pool kit are in range - salt at the moment is a bit low - about to put more in. Total alkalinity is 40ppm and needs to come up.  
Any ideas on what is happening and how to stop it - then what to do with what is there?

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## dynamictiger

I am not 100% sure on the information posted however I suspect the water proofing in the pebblecrete coating has done it's dash.  
I have seen something similar with a tiled pool and the cause was water leaking in between the tile and pool and pushing the chemicals out of the concrete at the old joints. 
This sounds suspicously similar.   
I would strongly suggest you ask a concrete pool bloke to come and have a look and give you a quote for a recoat.  Generally renders and so on have a 10-12 year life so you have done pretty well at 16.

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## Pugs

Pics or it isn't happening.... :Laugh bounce:

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