Gunite crack repair

[The wilt]

I have a gunite swimming pool that was installed 4 years ago. I live in an area that has subsurface limestone so the pool is basically shot over near solid limestone. The pool was finished in March.

When it got really cold the first winter (we keep the pool open all year) I noticed the pool was dropping. We have an auto fill device and the loss of water was more that the auto fill intake. My pool contractor determined there was a shell leak running across one corner of the pool in around 4' of water. His crew used a grinder to etch out the crack and filled it with something. Possibly plaster. The repair held till the next winter when it got very cold. The pool is leaking currently and this will be the 4th time.

I own a design build landscape company, we design pools with a lot of our projects and the company that did my pool does all my pools. He's the very best pool builder in our market and a real stand up contractor. He's willing to do whatever to solve this issue. The last time (not current time) this happened they used a very high psi cement product to fill the crack. Each time they grind the crack and fill it with something. It holds till it gets very cold. We've had a mild winter recently and it didn't happen that winter. The sub strata in our area allows the leaking water to simply run through the rock very quickly.

I'm on this forum hoping someone can shed some light on the issue. My contractor is doing his own research too. Anyone face a similar problem or have an idea of how best to fix the problem permanently? Thanks!

[RobLane]

Look into stapleing the sections together with kelvar or a similar idea.

[The wilt]

Thanks for the tip. Is the product kelvar or did you mean Kevlar?

[PoolDoc]

Crack repair on concrete pools can be difficult.

1. If the crack is a shrinkage crack, you can just fill it in -- no reinforcement needed.

2. BUT, if the crack is structural, and penetrating, then a "Kevlar" patch on top won't begin to do what you need. Most structural cracks move, as temperatures change. Resisting that movement takes some serious reinforcement. The photos below illustrate the sort of repair process that may be required. But even with that sort of work, if the stresses causing the crack are great enough, the pool shell will simply re-crack nearby.

The movement can be caused by sub-surface settlement or shifting; this is very common when the pool is built on fill dirt. If this is the case with your pool, you may not be able to stop the cracking, without resolving the underground problem, possibly by pumping concrete into voids between the pool and the sub-surface.

Bottom line: if you can find a GOOD local gunite company that is skilled in such repairs, they are the ones you need to talk to.

[The wilt]

Thanks for the detailed response. I'll pass this onto my pool guy!