Stain around fiberglass pool.

[I'dluv2]

Just found this place and it looks like lots of people that have the answers, which I need. We've been in our house over 6 years and love our fiberglass pool. They seem easier to keep up than gunite pools. But we have a problem hopefully we can figure out. I believe the pool was installed 15 years ago and there is a build up of some kind all the way around. It's hard and somewhat gray colored, and can't find anything that will remove it. In Arizona the water is terribly hard, everyone runs water softeners for their house. Thought the stain was a combination of things, chemicals, hard water, sunscreen etc. Change the water completely every 2 years.

A you can see in the pic the original water line is about an inch above where we keep it now. I even tried raising the level temporarily, letting it soak for a couple days and tried cleaning to no avail. Any and all suggestions will be greatly appreciated.

 

[Texas Splash]

Welcome to TFP! Is that area at the waterline rough? Have you tried (carefully) applying some muriatic acid directly to that stained area? Perhaps it's calcium scale.

Other than raising the water level, what other treatments or products have you tried?

 

[I'dluv2]

Yes it's somewhat rough like sand paper. Tried muriatic in a small area. Safety glasses, latex gloves, soaked an old sock, held on the area for about 15 seconds and then scrubbed, no luck. And something called Poli Ox, supposed to work on fiberglass boats etc. Nothing has made a dent in it so far.

 

[Texas Splash]

Interesting the acid didn't do anything. Since it seems to be limited to the waterline, I suspect a combination of scale and organic materials (scum, oils, etc) over time got trapped and embedded in there. You could try some light grade wet/dry sandpaper. Start at about 800 grit to see if that works. Go to a lower grit if needed. Always test in a small area and let it dry to ensure you're happy with the result.

 

[I'dluv2]

Saw somewhere else someone mentioned trying hydrofluoric acid. Don't know anything about it, not sure if it's been tried before.

 

[Texas Splash]

someone mentioned trying hydrofluoric acid. Don't know anything about it, not sure if it's been tried before.

Hydrofluoric acid can be quite dangerous on its own and requires proper PPE's - long sleeve, chemical resistant gloves and eye protection. Not something we generally recommend here at TFP. @JoyfulNoise may be able to expand more on that chemical and it's applicability for pools.

 

[JoyfulNoise]

You would be hard pressed to find a source of hydrofluoric acid and you wouldn’t want to use it anyway. It’s incredibly toxic and dangerous - splash HF on more than a square inch or so of exposed bare skin and you’ll be dead in a short time from cardiac arrest. Small splashes of HF can be absorbed and cause your bones to become embrittled and decayed. It is used in the glass blowing industry as well as a few others but you should never use it outside a controlled environment without proper PPEs.

Also, it probably wouldn’t help much. You can try a product called BioDex 300 which is known to remove hardened silica scale from pool tiles. It’s a mixture of mainly phosphoric acid with a very small amount of HF. I would caution to only use it with proper protective gear on and to do it at a time when you plan to drain and refill your pool anyway.

 

[I'dluv2]

You would be hard pressed to find a source of hydrofluoric acid and you wouldn’t want to use it anyway. It’s incredibly toxic and dangerous - splash HF on more than a square inch or so of exposed bare skin and you’ll be dead in a short time from cardiac arrest. Small splashes of HF can be absorbed and cause your bones to become embrittled and decayed. It is used in the glass blowing industry as well as a few others but you should never use it outside a controlled environment without proper PPEs.

Also, it probably wouldn’t help much. You can try a product called BioDex 300 which is known to remove hardened silica scale from pool tiles. It’s a mixture of mainly phosphoric acid with a very small amount of HF. I would caution to only use it with proper protective gear on and to do it at a time when you plan to drain and refill your pool anyway.

Thanks for the heads up, now I know why it was hard to find much info on it. This spring we will be draining the pool and will try the Bio Dex.