Total Calcium Hardness

by Kevin

What can be done to remove the rough surface on the pool walls. I have a 2 year old gunite pool and I have kept all the chemical readings within the parameters except for the Calcium Hardness.

It has been slowly increasing from 250 on day one to 800 plus as of today. I think the new plaster has stopped leaching, now that the pool is 2 years old. My local supplier tested it and came up with 650 but my drop test shows it at 1400.Not sure which is correct but its to high.

I plan on emptying the pool and filling it with household water which tested at 250. I would like to fix the rough plaster before filling. Any suggestions?

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Hi Kevin. First thing is to only use liquid chlorine or bleach. Your fill water is already hard so you don't want to increase it by using calcium hypochlorite. Liquid chlorine will handle 99% of your pool's chlorine needs.

The calcite from the plaster will continue to leach into the pool during the curing process. This can take several months to finish. The bad thing is the hardness can increase, along with the pH. This cannot be stopped and is usually a part of getting new plaster. When high CH and high pH are combined, it causes scaling. The higher pH will cause the calcium to precipitate out. This may manifest itself as a rough sandpaper like surface on certain areas of the pool. Warm water can also contribute to the problem.

The problem could be corrected without draining the pool. but it can take a a few months before a noticeable difference.

After inspection and determining the problem is scale, the pH and TA will need to be lowered and maintained using muriatic acid and a stain/scale remover would be used. This is usually nothing more than a metal sequestrant. Calcium is considered a metal. Jack's Magic or ProTeam Metal Magic are very good choices. Brushing the pool will also be part of the process.

The scale will slowly dissolve. At the end, some of the pool water will need to be drained from the pool because it will contain a high amount of dissolved calcium.

You probably know the other alternative. Draining and sanding the plaster to a smooth finish. If you go that route, the company that did your plaster job can help. They probably have the tools and equipment for the job.

Good luck and have a great Summer.

Robert