The walls of my 13 year old fiberglass pool have been chalking terribly this year. I called the manufacturer of my fiberglass pool and they claim it is probably caused by low calcium and high PH. I bumped up my calcium to 250 and have been keeping my PH lower and the problem has improved immensely. I still get a tiny bit of chalkiness on my hands when I rub the walls but the walls are smooth now and it no longer clouds the water when I brush the walls. I'm getting ready to close my pool and I'm wondering if I need to increase my calcium to 300-350 since that is the level my manufacturer recommends or keep it at 250 since that eliminated most of the chalkiness. I've got tile grout to protect and I want to protect my pool from stains but I wasn't sure how high it needed to be to achieve this. The calcium isn't dissolving well since the water is so cold so I don't want to add more calcium unless there is a reason to do it. Any advice would be greatly appreciated.
calcium and older fiberglass pools
- Thread starter al27
- Start date
Oly
Gold Supporter
Have you tested the amount of calcium in your fill water?
Run your numbers in Pool Math PoolMath and check the CSI, Calcium Saturation Index.
The CSI value is the pool water’s “balance.” Negative values indicate increasingly aggressive water while positive values indicate the water has an increasing potential to scale. Water that yields a CSI of between –0.3 and +0.3 generally is considered “balanced.” The goal is to avoid highly aggressive water that will degrade the pool surface and equipment while also avoiding scaling water, which can deposit scale on pool interiors, pipes and the like.
Run your numbers in Pool Math PoolMath and check the CSI, Calcium Saturation Index.
The CSI value is the pool water’s “balance.” Negative values indicate increasingly aggressive water while positive values indicate the water has an increasing potential to scale. Water that yields a CSI of between –0.3 and +0.3 generally is considered “balanced.” The goal is to avoid highly aggressive water that will degrade the pool surface and equipment while also avoiding scaling water, which can deposit scale on pool interiors, pipes and the like.
- Jun 22, 2014
- 47,929
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Al, others have described the same situation as yours. While not the hard, aggressive type of calcium scale we normally think of in pools, this other type that wipes with the hands has seen improvement with an elevated CH level and closely monitored pH. Since you will be closing soon, you might also take into consideration the amount of new water received from rain/snow (if uncovered). If the CH typically drops over the winter, you might consider bumping it up a little now before closing. Add calcium in slow amounts for best result.