Stains on steps

[Deeno01]

I have just started to look after a neighbours liner pool with the plastic steps. I have noticed on the steps that there are dark stains appearing randomley on the steps only. Where each stain appears, it has raised the platic and seems to give the impression that it has split the plastic.
There are no metal elements to the pool ie pools steps, and the pool is a normal liquid chlorinated pool. Chlorine is at 2.8 ph is 7.5, and the current pool temp is 20c.
I have added a picture to see if anyone has seen this before.

 

[pooldv]

Are those stairs fiberglass? That sounds like a fiberglass blister in the gelcoat from a defect.

 

[Deeno01]

Yes they are fiberglass. Sorry I always call them plastic. I am guessing that the pool is over 10yrs old, so would the blistering start to happen over a period of time, or is it something that happens when the pool is "just old"? Also is there anything that would have helped in progressing the blistering, eg high/low pH, calcium etc/
Thank you for your help as I would just like to know for future reference.

 

[pooldv]

I'm not sure what causes it. I believe that it is water infiltration through the gelcoat due to age. I don't think it is related to water chemistry. Same thing happens on boat hulls over time.

 

[Deeno01]

Ok thank you very much for your help.

 

[Alwayswantedapool]

I have the same thing on my fiberglass steps. Crushed (non coated) vitamin c pills will get rid of the stains for a couple of weeks. Then it comes back. Put the pills in a old sock or piece of t shirt and then whack them with a hammer a few times. Spots will rub off pretty quick.

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