Options for Lowering Calcium Hardness


Well-known member
Apr 14, 2013
Chandler, AZ
I've got a question on options for lowering calcium hardness in my pool.

We are located in Chandler, AZ which has extremely hard water (20 grains of hardness). We have a water softener on the house which provides nice soft water for showers, dishes, etc. Then we go swim in our pool and feel the hard water which results in itchy dry skin, etc. My current CH is 650+.

The recommendation here is to drain and refill your pool every two to three years because the TDS gets too high (or in some cases CYA gets, too high because of chlorine tablets, etc). In my case, my TDS/salt levels are above 4000 and my salt cell may soon shut down due to the levels getting too high. I only added enough salt when I last filled to get to about 3000 salt. It has steadily risen since then.

My options are::
  • Drain and refill, which will lower everything, but the refill will start me with water that's already at the high end of calcium hardness. I'll have to add salt and CYA back to get to correct levels. Surprisingly, water here is very cheap and it doesn't cost much to refill the pool - like $40. The CYA and salt are most of the cost for this option.
  • Have a mobile RO filter service come out for $600+ (one place quoted $750). This will give me perfect water and I'll start with a perfectly balanced pool. I'll still have to add salt and CYA as that is removed as well. The concern with this one is the price and how long that water would last as the fill water for top off would be hard and increase the CH over time. They mentioned that I would probably need to do it again in a couple of years as the levels rise. I'm not sure the $600 would be worth it every couple of years and how long I would actually enjoy a balanced pool before it started feeling hard again. One other option would be to install an RO filter on the water fill line to only add filtered water, but not sure if that would have enough pressure and output to work.
  • Is there a way to remove CH with clarifier that will also work with my DE filter? I'm wondering if I drain and refill, and then use clarifier to get the CH down, and then add salt and CYA to where I need. I can't vacuum to waste with my setup, so I would be doing a lot of backwashing and re-adding DE to the filter. I'm ok with doing that as DE isn't that expensive, but I don't want to damage my filter grids or cause more of an issue. I also don't know how much clarifier I would need to get the CH down and how long it would take.
  • I understand that flocculant is discouraged here and my robotic pool cleaner wouldn't work to vacuum it out.
  • A water softener for the pool would make the water soft, but would keep the TDS and salt high, requiring me to drain and refill (or RO) to keep it in check.
Any other options I'm not aware of?

I may just do a drain/refill this year, and then spring for the RO filter next year when I budget for it. My Hayward Ecostar VS3400 motor drive just went out last week (out of warranty, actually got 4.5 years out of it) with the stall error. I'm getting the Tristar VS950 for $729 from Hayward as that's what they are currently offering Ecostar owners with this problem. It's $530 just for the drive unit, so this makes more sense. I'll pay $130 for my pool builder to install it and get the 4 year warranty. That killed my option for spending an additional $600 on RO right now, but figured I would see if there was a less expensive option I wasn't aware of.

Thanks for any help!


Gold Supporter
TFP Guide
Jul 21, 2013
Northern NJ
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Your choices are drain the pool or RO. Clarifier or floc does not remove CH, CYA, or salt.

Using softened water for fill water will extend your time between water problems.
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