Reducing calcium hardness by precipitation

[Chot]

I understand the methods to reduce calcium hardness are generally to drain/refill with soft water or RO process. However, I was looking into possibility of precipitation to help pull it out of solution. This is discussed in other forums/articles but I can’t seem to find any info on this method in TFP forums. I really believe in the members here and it’s the first place I come to for questions/research on pool matters. I’m wondering what your thoughts are on this technique and it’s effectiveness/drawbacks as a way to reduce calcium hardness.

I actually discovered this effect accidentally last year when attempting to raise ph of my pool using soda ash after overdose of acid. It was my first pool. I observed the precipitate and then did some research into it. My well water is extremely hard.

Brief overview of method:
Raise ph of water using sodium bicarbonate/soda ash until dissolved calcium precipitates out of solution and then vacuum/filter calcium precipitate out. Raising ph to about 10 affects saturation index and lowers waters ability to hold dissolved calcium causing it to precipitate via ion exchange process.

Here’s a link to an article that discusses it.

How to Fix 'Milky' Pool Water (Without Draining)

How to reduce the calcium hardness level in a pool without draining.

aquamagazine.com

Please let me know thoughts....good and bad or otherwise.
Thanks

 

[mknauss]

Welcome to the forum!

Reducing High Calcium Levels in Pools

Many of us may have had the unfortunate experience of adding soda ash to raise the pH and turned the pool water a milky white… in fact, we refer to it as “milking” a pool. Why does that happen and what does that do to the water? Well, the soda ash (sodium carbonate) is normally very soluble in...

www.troublefreepool.com

True -- it can be done. But --

and that the calcium carbonate precipitate should not adhere to the pool surface if continually brushed and removed by filtration quickly.

Fully filtering out the resultant nano particle size calcium carbonate is very very difficult to nearly impossible with traditional filtration equipment.

IN the end, the cost of the chemicals involved plus all of the convoluted steps needed to make it work without scaling my pool walls with calcium was just not worth it. Lime-softening is a great treatment process for potable water distribution systems, not so much for swimming pools.

I suggest you read ABC's of Pool Water Chemistry.

 

[JoyfulNoise]

To do this properly, one should use lime (calcium hydroxide) and sodium bicarbonate. The lime softening process has been known for centuries. BUT, it will be all but impossible to pull off in a swimming pool without causing scale to precipitate all over the pool surfaces and possible damage and plug up your filter.

Even here in the desert Southwest where monthly water bills can easily exceed Car payments on ones budget, draining and refilling a pool is almost always cheaper than any other process. Draining and refilling my 16,000 gallon pool could easily run me $300-$400 and that would be about 2/3rds the price of RO processing the water.