White stain or bleaching(?) on fibreglass

Stains on the pool surfaces, pool equipment
or on the swimmers, or off-color swimming pool
water. Discolored but clear pool water.
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My Pool: 50,000 litre fibreglass

White stain or bleaching(?) on fibreglass

Postby jimmyj » Tue 25 Jun, 2019 19:17

I have a fibreglass pool about 3 years old, and over winter a year ago it started getting a white hard coating on it.

I had a pool specialist in, who ended up dropping the pH to acidic levels (around 3.5-4) which removed a good portion of the white colour (it was still white-ish, but was a faded white and you could mostly see the blue gel coat underneath which I was ok with) The white also had hint of brown in areas, which he said was just dirt in the pool trapped in the white. From memory it was something to do with calcium hardening, however calcium levels are low. The white shows in patches on the steps and bottom of the pool too.

The problem however is when we pulled the pH back up to around 7, a couple weeks later the white came back.

It's definitely something in the water chemisty, as you can see the normal light blue sides below the coping, then just above the water level (I dropped the water level to show the discolouration) you can see it's white. The white is a very hard coating, and cannot be scrubbed off at all. I could drop pH significantly again, and probably remove a lot of it, however it seems pointless doing this as I know it will just come back again, so need to determine the root cause. I've tried a double dose of Scaletec (calcium descaler) to no avail (although it may have only slightly helped)

This is what is looks like


Any ideas??? What is in my water that is causing this?!!!

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Re: White stain or bleaching(?) on fibreglass

Postby Teapot » Tue 25 Jun, 2019 23:19

Can you post a full set of water test results, not using dip strips as they are pretty much useless

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