Removing calcium from pool water using a water softener?


Jul 29, 2010
Hello all!

:idea: From time to time I get crazy ideas, and I wanted to run this past those who probably know more about the subject than I. I live in lovely S. California where the calcium hardness is 340 right out of the tap. Obviously I am trying to control my CSI to ensure that scaling will not happen for some time, but it occurred to me that although reverse osmosis or replacing water are both fine ways to control CH, a water softener hooked up to a submersible pump might just suck the calcium right out of the water. My understanding of how it works is that the calcium & magnesium in the water would be replaced by sodium when it is run through the filter resin. I assume that I would have to leave the device hooked up for about a week or more to reduce the CH to an acceptable level. After that, I could hook up the water softener to the main line in the house and then every time I refill the pool, it will be with "soft water". I doubt it would eliminate the calcium issue entirely, but I bet I would be able to go much longer without having to drain the pool.

My concern is that too much sodium in the water might be just as bad as too much calcium. does anyone have any thoughts/experience they can share?



TFP Expert
LifeTime Supporter
Jan 6, 2010
San Dimas, CA (LA County)
Any moment now Simicrintz will be posting....He runs a reverse osmosis service out of San Diego. When it's done, you'll have essentially distilled water in your pool. I keep meaning to have it done, but I had some unexpected expenses and I'm not sure he'd make the drive all the way to my place. Maybe in the off-season. But hey - if you're close, maybe he could make two stops on one trip!


Wow, Richard; am I that predictable??!

It is weird that you ask this question, loudog, 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+ :shock: 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).

One day I will drive up and treat Richards pool (and, from reading his posts, have a good laugh or two!), and I would love to head to your place next! Hopefully you guys live close to each other, 'cuz I think I'd probably only cover my fuel costs doing the work :cool: Ah, the life of a pool guy.......


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
loudog98, welcome to TFP!

Using a water softener will indeed allow you to go longer between drain/refill or RO treatments. Keep in mind that water softeners are not really designed to process the quantities of water involved in a swimming pool, so you need to run it slowly and continuously for a long time to have a significant effect and that will require many recharge cycles. Eventually, as simicrintz points out, the salt level will get too high. But since salt can safely go higher than calcium can, that will take longer than it would take for calcium to get too high. Of course, once you take all of the costs into account this approach isn't really any less expensive and it certainly is more complex.


Well-known member
Apr 15, 2010
Las Vegas
Loud98- I have my water softener plumbed to soften my whole house, hot and cold (the right way, we could start a whole thread on this) I chose to plumb the back faucet that runs the autofill soft as well. My tap water was quite hard, also we have a LOT of calcium in our water, as evedence by the white band around lake mead where the water has dropped. Cities also use chlorine to kill bad things in the water and garantee(best they can) safe water at the tap. In Vegas however we have approx. 3ppm chlorine come from the tap! After adding the softener everything went down, Including the chlorine almost to zero.
So If you do this exparement know that a good softener will take most of your chlorine out too! I do like your idea. I think for sanatary purposes id never connect the softener to the drinking water lines after using it this way, but $350-550 new is a good price for a filter idea like this.
Jason it right it would take some time. but it could be a cool experiment. On my waterboss 900 i can set the grains of hardness on the display from 1-90. It is a demand softener with a nice digital display I will rechage about every 100 gallons if i jack it up to 80. At the lower settings it will run 900 gal. before recharge. It shows a run down in gallons for availabe softwater, and some other stuff.
I should do a test on some untreated water and treated water with my new DPD-FAS kit and see how much of what my softener is removing and post the results.

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