Cracks! Too worry or not? (With photos)

[nicksab]

Hi all -

Our 1961 18x35 gunite pool has been partially drained for 2 months during a major renovation by a pool contractor. We were told that the pebblecoat was in good shape before it was drained. Now, it has developed hairline cracks that emanate from a point in the shallow end. One of the cracks spreads more than halfway to the other side. See the attached photos to see what I mean.

The pool guys claim the cracks were there when the pool was drained. I'm pretty sure I would have noticed the cracks right away, so I'm concerned they've appeared since the water level was dropped.

Please help me with the following questions:
1) What would cause cracks like this? Is it possible they've been there all along, or more likely that they happened since the water was drained?
It is important to note that here in Atlanta it has been unusually cold, including multiple days of hard freezes - teens overnight, staying below freezing during the day. I worry that the temperatures may be to blame somehow.
2) What, if anything, should we do about the cracks?

Frankly, if the cracks are merely cosmetic, I don't care. They won't be visible when the pool is filled. I just worry that these cracks are a symptom of some bigger issue. One theory I have is that water got below the gunite shell, froze, and pushed up to create a pressure point...but I'm no expert.

The current plan is to refill the pool until the water is above the cracks, then do a dye test to see if the cracks draw water in. If they do, my pool guy plans to patch them somehow.

Any ideas you have would be greatly appreciated.
(I searched the forum for these answers but really wanted a direct response based on my photos and questions.)

Thanks much!

 

[carolina pool]

My guess is that the finish has delaminated. You could determine this by tapping the area with the plastic end of a screwdriver and see if it sounds hollow.

 

[nicksab]

Thanks for the reply. I get what you're saying and will try the tap test tonight.

If it is in fact delaminated:

• Would you guess this problem happened since the pool was drained?
  How big an issue is it? Should it definitely be repaired? Or will it maintain if we just refill it? If it needs to be repaired, I assume

that means removing and replacing that whole area?

 

[carolina pool]

Yes it has to be repaired.

Draining it and leaving it drained certainly exacerbated the problem although it probably wasn't bonded well to begin with. It could be that the underlying plaster is the problem. If the pool was built in 1961 its very possible that there are numerous layers of finish material in place. The only way to find out is to chip it out.

 

[nicksab]

Just wanted to follow up and share what we did about the cracks.

As suggested, my pool tech and I did the "tap test" to see if it sounded hollow as a sign of delamination. There were no hollow sounds, nor changes in the nature of the sound when tapping in the cracked or uncracked areas. So we decided it was not delaminated.

We filled the pool above the cracks, did a dye test, and saw no signs of leaking. So we decided to leave it as-is and fill the pool the rest of the way. We have not experienced any problems since.

I will say that the cracks are quite obvious when you look into the filled pool, and we would have noticed them if they were there before the pool was drained. It's clear that the cracks appeared while the pool was empty, I'm guessing as a result of the very cold temperatures we experienced for extended periods here in Atlanta.