Frustrated with calcium levels in pool - may be time for water softener

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MannyCPA

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Feb 22, 2017
55
Tampa
Currently live in Tampa, SWG pool was completed 4 months ago, we have no screen enclosure, and the heater has been set for 90 degrees 2 of the last 4 months (i.e., we’re getting a lot of evaporation). I’ve had no issues maintaining FC, TC, pH, TA, and CYA. Unfortunately, my calcium levels have been on the rise for past 2 months. We started off at 250 PPM (which is where my tap water sits), and just hit 600PPM. And serious calcium scale/flakes are starting to accumulate in the bottom of the pool (see picture below).

I’ve read an encyclopedia worth of information on this website, and what I’m gleaming is I can’t win this fight!?! If I empty out pool water and fill/dilute with 250 PPM tap water, the best I can get is 250PP, but the heating of the pool and evaporative affect will cause a steady rise in calcium levels eventually (took 2 months to triple). In the summer it rains a lot, so that should have a dilutive effect on the calcium, but that solution is highly dependent on mother nature and it’s cyclical. I’ve also read that flocculants and clarifiers don’t’ work. Would a whole house water softener do the trick?

rpP5sic.jpg

WM5IZes.jpg
 
Can you complete a signature so we know what pool type, volume, equipment, etc you have?

That level of CH rise is hard to imagine from evaporation in that short of time. It takes ~16 months for my pool to triple in CH as our fill water is 250 CH. To do that in 2 months, you have evaporated your entire pool volume over 2X. Did you add that much water over that time?

Only other source of calcium is either Calcium Hypochlorite (did you use that product?) or very negative CSI dissolving your plaster.
 
In the past 4 months I’ve had to replace a third of the volume in the pool, so that’s definitely not the culprit (weather is in the 60’s, sunny, with low humidity). I’ve never used calcium hypochlorite, but it’s possible the horrible pool cleaner we used for the first two months while I was traveling did. Maybe it’s negative CSI dissolving plaster, but I don’t test for salt or borate so I’m not sure what my CSI is. Looks like I’ll have to order…

13000 gallon pool and 800 gallon spa
Pebble tech finish
Pentair IntelliChlor IC4
Pentair S7MD 72 D.E FILTER
Pentair 140 BTU Heater
2 Pentair intelliflow variable pumps
Pentair screen logic system
 
As you have a SWCG your salinity is close to 3000 ppm. Does that SWCG provide a salinity output? Borates, unless you have added them, are not in the water. So enter your test data into PoolMath and see what your CSI is. You can post up the results here and we can take a look.
 
Nope -- that would be an extreme scaling tendency. Can you post the numbers you used. Something sounds off.
 
Starting with 250 ppm calcium and increasing by 350 ppm would require evaporation of about 1.4 x the pool volume or 19,320 gallons of water.

At 90 degrees Fahrenheit, the evaporation will definitely be accelerated with no cover.

How much evaporation per day are you getting?

How deep is the pool?
 
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You need to get the TA down. I would recommend that you keep the pH down to 7.2 until the TA comes down.

Then, try to keep the CSI between about -0.3 and 0.0.

At 90 degrees Fahrenheit, you're going to get a lot of evaporation.

You should use a cover to reduce evaporation, which will save you a lot of money on heating costs and significantly reduce water loss and replacement.

You might need to get a water softener for the fill line.
 
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As James says, the high TA, high pH, and high temperature really drive your CSI up. Do you get a significant amount of white calcium flakes out of your returns from the SWCG? I sure would if I had that high of TA. I can tell when my TA gets above 80 ppm, the white flakes really start.
 
Trying to maintain 90 degrees water temperature with an uncovered pool, I would estimate that the heat pump would need to run at least 9 hours per day just to keep up.

Is that about right?

Do you have a way to monitor the amount of water being added?

The amount of heat lost due to evaporating 1.4 x the pool volume would be about 168,441,907 btu, which is about 1,203 hours of heat pump run time or 20 hours per day for 60 days.

How long does the heat pump run for per day?

How much does the spillover run per day or week?
 
Last edited:
Manny,

That's very hard tap water! We have similar levels over here in Stuart for well water. I have added a whole house softener just to protect the plumbing and fixtures. It works great! That said I'd also offer the following for your consideration on the pool issue:
  • First do everything possible to minimize the evaporation. I would definitely second Jame's suggestion of a cover. Surface wind can have even more impact on evaporation than temperature. A cover would help a lot.
  • Once you get the evaporation rate minimized see if you can quantify the water consumption and use that to size a dedicated softener. Even if you have to do the calculation using James' novel concentration change method it is probably good enough. This would make more sense than using a whole house approach because the water in your pool should have some CH to protect your plaster and grout. You can split flow around the softener to accomplish this. Some even have an internal bypass Water softeners are usually designed to regenerate every 5-10 days but that's not really a requirement. It just a guideline and usually results in a resin life of 5-10 years.
  • A mobile water softener is missing the automatic regeneration control head. So every time you regenerate you'll have to do it manually. This could be impractical unless you dramatically reduce evaporation. If you're unable to reduce evaporation you'll be "concentrating up" about 5000 grains of hardness. every day. To keep CH from rising you'll need to take about that much out once you get your pool to the desired CH level. That will require a manual regeneration every 2-3 days for the unit. Superb for a spa but a little more work than I'd want to do for a pool. On the other hand if you're able to dramatically reduce evaporation this option might work very well.
I hope this is helpful.

Chris
 
Being in West Texas, Abilene to be exactish, we probably have some of the hardest water on the planet. I've tested it straight from the tap and it tests at ~240 PPM (about 14 grains). Using my Lamotte test kit, I'm getting readings of 570 to 625. I keep the ph and alky right in line daily and have never run into what you are experiencing. My CSI has never been higher than .60 ( at .2 I start doing what I can to bring it down) and never lower than -.6 (at -.2 again I start doing what I can to bring it up). I test it every single day...sometimes twice.My pool was completed in November so who knows come September or so, I may be filling it in. LOL

I would imagine there would be some business around you that would supply tanker size trucks of near 0 CH water. In the northeast this is no problem as the water up there is generally soft. Down south, not so sure and also not sure of the cost.

Good luck!!
 
Sizing a softener is easy, get 64,000 grain and call it a day. They come with meters now and Regen only when needed. I honestly can't remember my fill ch but it's in the 250's, with a 64,000 grain I get almost 3000 gallons per a Regen, so I can top up my pool in the spring on 1-2 regens and add water every weekend without watching the meter on the softener.

Soft water on dishwashers, skin, faucets, etc, you need a softener
 
Appreciate all the insight. My takeaways from the last dozen posters is to:

  1. Lower/balance out the TA, pH.
  2. Minimize evaporation
  3. Consider a water softener

All these are in play. I got the TA and pH down and the flakes went down significantly. Evaporation is just something we’re going to have to deal with, unfortunately. The pump and waterfall run 12 hours a day (8 to 8). My wife and kids want the pool at 90 degrees during the winter (pool gets used daily). The pool is on the south side of the house with no screen enclosure so summer temps will hit high 80s easily. And I’m not terribly interested in covering the pool considering how frequently we use it. I’m very interested in the whole house water softener so we’ve reached out to Culligan and some other local shops.
 

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