Hairline cracks... Normal or not?

[DanaSC]

We've noticed some hairline cracks in our gunite recently. It's been about six years since we've had it resurfaced, which seems a little early for problems like this. Is this normal, do you think?

 

[YippeeSkippy]

As long as they're hairline, and you don't think its gone thru and causing water loss, I'd say it looks ok. Keep an eye on it, especially that darkened spot that looks like a small piece of plaster has broken away?

Maddie

 

[tstex]

Do a bucket test or do you know if it seems like you are losing water?

we have a lifetime warranty on our gunite pebble tech as an original build and owner...check w your resurfacing comp and see what they say? Have them come out and take a look at it...good luck

 

[pooldv]

It is not uncommon to have an occasional crack in the plaster. Especially, if you have clay soil. We've got black clay soil and our pool moves a bit. Gunite can flex a little more than plaster can which can cause a crack in the plaster when the soil moves. We've had 3 or 4 cracks since the pool was built in 2012. One from 2013 leaked enough to make the water bill noticeably bigger from the autofill. Our PB used pool putty two part epoxy to fix the cracks, it cures under water and it hasn't leaked since. Maintaining even moisture content around the pool will help a lot to reduce lol movement. We use a micro-irrigation system on a timer around the pool to maintain soil moisture levels.

 

[DanaSC]

Thank you all for the input. I am concerned about that dark spot. I've got another thread going in the algae forum about the possibility of black algae. One of my concerns is I failed to keep calcium high enough through the winter (totally kicking myself now) as we normally cover the pool but this year we didn't and I just never even thought about it. I'm concerned that maybe the calcium being too low for too long has caused this problem. Do you think that's a possibility and that I've done permanent damage to the pool surface? And do you think that black spot could be the plaster wearing away rather than black algae? There are other black spots in the pool as well, which is why we wondered if we had black algae. These spots started showing up last season, though at that time the calcium was under control.

 

[pooldv]

The only real damage low calcium can cause to plaster is called etching, which is pitting of the surface caused by calcium being leeched into the water. This can result in a rougher feeling surface. It takes the right combination of low CH and low pH resulting in a low CSI indicating the water is corrosive.

More here about black algae, Pool School - Black Algae

More here about etching, Pool School - Calcium Scaling

If the plaster does become etched that is a permanent condition but you can sand rough areas to make them smoother using wet/dry sandpaper.