I softened my pool using a Kenmore water softener

[gerombo]

Hi all,
I'm a new pool owner in California. As I learned so much from the community here, I wanted to give back, by registering to the forum and sharing my experience after the first couple of months.
The main challenge I faced was high Calcium Hardness (1000+ppm) in my plaster outdoor pool.
I couldn't find anyone offering reverse osmosis in my area (although both gentleman were super friendly and helpful), nor was I willing to waste over 25000 gallons of water during a drought.

So last summer, despite the various comments advising against using a water softener I gave it a shot (or let's say quite a few shots).

Short version

Before softening:

CH: 1000+ ppm​

Salt: 2600 ppm​

CYA: 100 ppm​

After treating my pool with 85 cycles on my Kenmore 350 water softener and about 400 pounds of salt:

CH: 240 ppm ( -760 ppm hurray!)
Salt: 3600 ppm ( +1000 ppm)​

CYA: 60* ppm (I noticed a reduction in CYA but I also experimented with the Bio-active cya reducing bacteria, so I can't say if it can be attributed to the softening process)​

Long version / main challenges

1. move water - Hard pool water needs to be pumped out of the pool, through the water softener and back in the pool

• pump - I should have used my pool pump, but I wasn't keen on the electricity bill, nor on the plumbing it would have required. I ended up using a 1/4 HP submersible pump from home depot (don't do this). I found out the hard way these pumps are good for high flow rates with large pipes, but do not generate a lot of pressure (<6PSI). My softener needed at least 7 PSI (iirc) to be able to regenerate (rinse the resin beads in the tank to flush out the calcium with salt brine), which my pump couldn't do. Also the pump housing fully corroded from the salt in the pool.
• pipes/hoses.- I used 3/4" garden hose for the feed line (pump to softener) and the return line to the pool. This is not great for submersible pumps as it restricts flow (which becomes increasingly important after a while). I ended up moving my softener right by the edge of the pool to minimize the hose length. (and I learned about hose thread and pipe thread NPT standards)

2. soften - water flows through the softener tank with resin beads, calcium "sticks" to the resin

• I used my household Kenmore 350 water softener. I removed it from the house water supply and added in a bypass. I moved it closer to the pool to minimize hose length. (the water softener is back in the house and working excellent)
• testing - the biggest challenge is knowing if the water softener is actually working well.
  When the softener was working well 1000 ppm pool water went in and 5-10 ppm water came out. However initially I wasted endless cycles where water was flowing without it getting soft.
  I ended up using Calcium hardness test strips both 0-1000ppm and 0-400 ppm range to measure the output of the softener at regular intervals (initially 10mins).
  I also used a Taylor K-1770 test kit to measure softening progress in the pool itself every 10 cycles.

3. regenerating - the resin beads in the tank are saturated with Calcium and need to be rinsed with salt brine.

• the softener has an input water hardness setting (expressed in grains of calcium 1g = 17ppm), and would automatically regenerate after a certain volume of water had passed through. the softener would be saturated long before that. (hence testing was important to discover the trends)
• auto regeneration failed because of the lack of pressure my pump could generate. I switched to city water (>40psi) for every regeneration cycle and then back to pool water. This is unfortunate, because this brine water drains to the sewers (should ideally be pool water) and took manual effort.
• I used about 400 pounds of salt. Don't add a lot of salt at once. The salt level dropping is a key indicator things are working.

4. rinse and repeat - Some numbers:

• pool went from 1000> 240 ppm in 85 cycles using 400 pounds of salt
• in the process I added about a 1000 ppm of Salt back into my salt water pool
• Every cycle removed close to 10 ppm of Ca from a +-27000 Gallon pool (in absolute numbers thats about 16.000 grains/cycle)
• I used about 400 pounds of salt to remove a total of 1.2 M grains. That's about 3000 grains removed per pound of salt which is slightly above the Kenmore rated minimum salt efficiency.
• My pump was able to achieve about 200 Gallon per hour flow rate (and 260 Gph with shorter hoses)
• Because the total pool hardness reduces with every cycle, the amount of water that has to be treated to remove the same amound of Ca increases with every cycle. The first 10 cycles (pool at 1000ppm) each lasted an 1hour, treating 2000 Gallons, before needing to regenerate. The last few cycles (pool around 300 ppm) lasted around 3 hours, treating about 6500 Gallons. Regeneration cycle duration is fixed with the excpetion of extra rinsing and backwash etc, you can disable all of those to reduce the regen time.
• The pump consumed about 55 kWh of electricity in total.

It was an adventure, I learned about pump flow rates and discharge head, about venturi elements and salt bridges and not to forget hose vs. pipe threads .
Next time I will for sure try a high pressure pump.

Happy to provide more details to anyone interested.

 

[Texas Splash]

Welcome to TFP! I did something similar a few years ago with my Kenmore and just last year ended up changing the resin in my softener. Excessive regens will do it. Good you were able to lower that CH. Now you should be in an ideal position to manage all water parameters as long as you are testing with a TF-100 or Taylor K-2006C test kit. Be sue to visit our Pool Care Basics page and update your signature with all of your pool and equipment info. Enjoy the forum.

 

[wireform]

As Texas ^^^^^ already mentioned the resin issue I'd make sure the resin is capable of doing its job here on out otherwise you'll be sending out hard water throughout the house.

 

[Flying Tivo]

I check CH after my softener every month, but my resin is quite new. They say anywhere from 5-10 years for resin exchange depending on hardness and chlorine in city water. If you use a carbon activated filter before the softener it should help to get to the 10 years.

 

[JoyfulNoise]

The thing to understand about ion exchange softening efficiency is this - it is the ratio of sodium ion to calcium ion concentration that will determine efficiency. Normally speaking, potable tap water has a very low sodium ion concentration compared to mineral hardness. So when you use city water in a softener, that standard value for grains per gallon removed applies.

Pool water is not potable water. If you look at your input conditions, the water you are treating has about 4 times as much sodium in it as calcium on a molar basis. Even though the softener resin has a slightly greater affinity for calcium ions than sodium ions, it’s not huge and so a large Na/Ca ratio makes it harder for the softener to operate. As well, the insufficient rinsing and backwashing contributed to an increase in salt levels which makes the process less efficient. This is why you were seeing less softening as the process wore on. The resin simply couldn’t exchange ions efficiently.

All water treatment processes have a limit on the allowable TDS for the input stream. Ion exchange is usually a “final polishing” process and not a raw water input process. Membrane processes (RO) can usually handle a wider range of TDS (with higher levels of rejection to waste) and vapor compression distillation has some of the best efficiencies … but also costs a lot more in energy.

Glad you were able to lower your CH. You probably took a couple of years off the life of that softener but that’s ok as long as you are aware of it. Give a few good regeneration cycles before you put it back into service and I would even suggest you run a resin cleaner through it as well. Pool water has a lot of nasty stuff in it and resin cleaners have biocides in them to kill off any biological contaminants it may have picked up.

 

[gerombo]

If you look at your input conditions, the water you are treating has about 4 times as much sodium in it as calcium on a molar basis. Even though the softener resin has a slightly greater affinity for calcium ions than sodium ions, it’s not huge and so a large Na/Ca ratio makes it harder for the softener to operate.

Agreed. I was actually surprised it still worked this well.

As well, the insufficient rinsing and backwashing contributed to an increase in salt levels which makes the process less efficient.

This sounds logical, I could not see this in my measurements (I logged for every cycle the duration until the output water was hard) but since this wasn't the main focus of my logs, I would not exclude there was a reduction in efficiency when i played with the rinse settings.

You probably took a couple of years off the life of that softener

very likely. it is still working well though

Give a few good regeneration cycles before you put it back into service

I did with some extra rinses and backwash

I would even suggest you run a resin cleaner through it as well

I saw somewhere you could also remove the resin from the tank and wash it but wasn't aware there's resin cleaner. Thanks for the tip!

 

[JoyfulNoise]

in from the tank and wash it but wasn't aware there's resin cleaner. Thanks for the tip!

Most resin cleaners can be added to the brine tank just before a regeneration cycle. You want to get one that contains both phosphoric acid (to remove metals) and a quaternary ammonium biocide that also acts as a detergent and surfactant.

 

[gerombo]

Welcome to TFP! I did something similar a few years ago with my Kenmore and just last year ended up changing the resin in my softener. Excessive regens will do it. Good you were able to lower that CH. Now you should be in an ideal position to manage all water parameters as long as you are testing with a TF-100 or Taylor K-2006C test kit. Be sue to visit our Pool Care Basics page and update your signature with all of your pool and equipment info. Enjoy the forum.

thanks!
yes after getting started with a few test strips and a simple kit, I got the taylor kit.