Removing calcium from pool water?


Jun 10, 2010
Southern, CA
Topic split from 3 year old thread to create new thread. Please start a new topic when asking a question. Bama

It is weird that you ask this question, since I was just at a pool this afternoon that had exactly that scenario. Their CH was 250, in about 7 year old water, however, their TDS was 6,500+ Additionally, they have a pretty hefty water bill from the waste incurred from the salt system and are running the risk of corrosion from the high salt level. They have to make the decision now to drain or treat the water to drop the salt levels. It kind of seems that they just traded one problem (high CH) for another (high salt/TDS).
I have a salt system.
Salt test says 4000PPM. CH 1100PPM
(Southern, CA. fill water is really high - just keep adding more CH)

How does trading high CH cause high salt?
Were they using a softener?

Tell me about the RO systems.
What does/do they remove?
What do they leave behind.

What's the cost benefit tradeoff vs drain and refill?



Water ($125)?

Bama Rambler

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TFP Expert
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LifeTime Supporter
Jun 22, 2009
SouthWest Alabama
Trading CH doesn't cause high salt. Using a water softener adds salt to the water instead of calcium. Since salt is more benign it's not nearly the problem that CH is. However if you use the softener exclusively to replace water AND you have a swg it can become more of a problem as you will add enough salt with the softener that you'll have a salt level higher than the swg likes.

RO systems take nearly everything out of the water. Salt, CH, CYA, etc.

RO is expensive and only available in very select places. Most RO treatment companies have rebalancing the water as part of the cost, but I don't think it includes salt for pools with a swg.

If you do a drain and refill you still may have high CH, depending on the fill water.
If you can procure low CH fill water then a drain/refill will probably be a good choice, and probably be less expensive than RO.


LifeTime Supporter
Sep 11, 2010
Orange County, CA
I'm also in So. Cal and have high CH. I think right now I'm running about 525-550.

I did a partial drain and refill maybe 2 years ago, but the CH level doesn't take long to get back up there. I asked some people here on the forum about high CH and the answer I got was that if I'm keeping my water balanced, that I can probably get away with the high CH.

I have a chemistry system. The acid part of it works very well and keeps my pH in check (the ORP part is worthless). I'm pretty sure that's what saves me with my high CH. Before I replastered my pool and installed the chemistry system I always had trouble with high pH and hadn't found TFP yet. At that point I didn't know anything about CH or water balance, and I was getting calcium deposits on the pool walls. If only I'd found TFP sooner, I would've known more and the previous replaster probably would have lasted longer (I don't know the age, but I'm guessing it was ~25 years old).

I have a friend who works in the water industry that gave me a tip: at different times of the year they switch water sources between rivers and wells. He told me when my residential water would likely be pulling from a softer source, so it would be better to do my partial drain/refill at that point.


TFP Expert
LifeTime Supporter
May 10, 2010
SW Louisiana
One thing to keep in mind about RO systems is that a certain percentage of the water processed is lost down the drain (about 1/3 to 1/2 last I checked, but the technology continues to improve every year), this water is used to "wash" the RO membrane filters, otherwise the filters would become clogged with the salt/calcium deposits. Another thing to remember is they are somewhat expensive to operate, not only is the equipment expensive, but they consume a fair amount of electricity and the membrane filters have a limited useful life.

Without getting into the technical details, on a positive note given the developments in the RO industry over the last several years I suspect it may now be possible to build an RO desalination (also CH removing)system practical to be installed to produce low CH fill (top off) water from municipal water supplies at a rate of about 1/2 gallon per minute or so (30-40 gallons per hour), and a waste water production rate about the same (40-50% water loss) at an electrical cost comparable to running typical 3/4 HP circulation pump on high. At a build cost of under $1,500-2,000 , and an annual parts cost of maybe $100-$200, maybe much less with a bit of ebay scrounging etc. And prices are likely to continue to fall. This starts putting RO that can effectively treat hundreds of gallons of water per day within the reach of typical pool owners, however as always electrical cost will continue to be a significant factor. Of course commercial turn key units are likely to cost 2-3 times more than the above estimate, at least for now.