How do water softeners know when to regenerate? Time-initiated vs. Demand-initiated

by Stuart P Published 6.10.2013

Once people learn what water softeners can do to improve water quality, they often ask specific questions about the regeneration process. One of the most common topics is how the softener knows when to regenerate itself. Let’s examine two major categories of water softeners, time-initiated and demand-initiated.

Time-Initiated

Regenerating a water softener based on time was one of the first methods developed for automatic operation. Timed units put an end to the days when the softener operator had to start the softener by hand. Many of these control valve designs incorporate either a motorized or digital clock which has selection options for both the start time and number of days between regenerations. When this type of softener is regenerating, the control valve opens a path for untreated water to go directly to the taps. The clock is often set to start regeneration in the middle of the night to minimize the amount of untreated water going to the faucets or into the water heater. The regeneration interval must be a number of whole days and can be as often as every night, or as infrequent as one week or more. Careful thought must be given to selecting this interval to prevent either salt waste or hard water going to the taps.

Consider this analogy of refilling your car’s gas tank by using a clock. After estimating how many miles you usually drive, and taking into account the size of your gas tank, you may decide to add 12 gallons every four days at noon no matter what. If you drive less than usual, you will overflow your gas tank at the pump. If you drive more than usual, you’ll run out and be stranded in the middle of a trip. 

Illustration of a man filling up his car at the gas station while another man pushes his car down the street

Time-initiated softeners must be set based on estimates of water usage. If you have extra people visit, do extra loads of laundry, bathe your dog, wash your car or fill your kiddie pool more than what was planned, the softener will deplete and begin delivering hard water to the taps. Likewise, if you go on vacation and use no water at all, the time-controlled softener will regenerate needlessly and give you no value for the salt and water used each cycle. What is often done in practice is to be somewhat generous with the regeneration schedule, and plan for the worst case. This prevents hard water breakthrough for some cases of unplanned over-use, but is more costly to operate than a perfectly adjusted system. 

Some softeners have sensors that can detect when regeneration is needed. These override the clock to some extent, but the unit still has to regenerate itself in the middle of the night in whole-day increments. This still the leaves the possibility for unexpectedly high or low water use in that one-day period to make a softener regenerate too late or too early. Still further sophistication to the time-based system adds an automatic adjustment of the salt to increase efficiency.

Demand-Initiated

Demand-initiated water softeners start their regenerations when the capacity is depleted, which could happen at any time. It’s like filling your car’s gas tank when the gauge says it’s empty. A meter integral to the control valve totalizes water passing through the system. Based on how hard the water is, the meter is adjusted to start regeneration when the softening resin reaches the end of its usefulness. When the meter gives the signal, the control valve begins a sequence of regeneration steps, which typically include drawing in brine, rinsing and backwashing. Afterwards, the tank is ready to put back into the service stream and soften again.

Some systems using demand initiation have small tanks and short regeneration times. That’s how they limit the passage of hard water going to the end user. Other demand systems have a second softening tank which goes into use as the other tank begins its regeneration. This system allows virtually no untreated water to escape to the end user. Both types of demand systems get consistently good salt efficiency since the resin beds are fully depleted and “hungry” for the salt being used every single time they regenerate. More softening capacity is captured in a fully depleted bed than a partially depleted bed just like a hungry person is more likely to finish their dinner than one who just ate.

Comparison / Conclusion

We’ve explored some basic differences between softeners using timers and those using demand-initiated regeneration. Perhaps knowing these differences will be useful to you if you ever seek water treatment for your own home or business.

Contact Stuart P.


It wasn't the soap, it was my water!

by Guest Bloggers Published 6.22.2012

L. Heiden has been in the water treatment business for more than 25 years. Currently, she is a National Account Executive for UL and is an active member of the Water Quality Association.

Before my 25 years working in the water treatment industry, all I knew about water was that it was wet and I liked to swim in it. As a child I lived several different places but the one I called home was my grandparent’s house in a small village in Northeastern Ohio. This was the home that my father and his siblings grew up in and eventually where I spent my teenage years.

As a teenage girl I took lots of showers. I remember we always used a beauty bar soap which was supposed to be made with “¼ moisturizing cream.”  Funny, but I also remember my skin feeling tight and dry and because of that, I always felt that this was bogus advertising.

As a young adult with a husband and new baby, I lived in the same house in the small village that I grew up in.  I finally got to choose which soaps I wanted to buy and use. I knew one thing; it would not be that bogus soap with the cream in it.  Well, it turned out that no matter what soap I bought, I always had that dry tight feeling after showering. To try and combat this, I’d pour on the lotions and goop up my baby girl with baby oil. This was only a temporary fix.

Eventually, my husband and I bought a house in the country, about fifteen miles away from the house in the village where I grew up. The water in the country was very different. Instead of that dry tight feeling, I was left with a sticky, filmy residue after showering.  It was at this time in my life when I was first introduced to water treatment.  It was like a light clicked on in my head when I started working at Kinetico. I finally learned why there was such a difference in my water when I lived in the small village versus the water in my home in the country. The house in the village was on a city water supply which took water from seven different wells (not always the same ones) every day and chlorinated it to make it safe to drink and use.  This chlorine was the source of my dry tight skin when I lived in my family home; the same feeling you get after swimming in a pool! The water in the country was supplied by a private well on our property. This water was not chlorinated so I did not get that dry tight feeling. However, it was loaded with iron and had a lot of hardness made up of calcium, magnesium and other minerals. The hardness in the well water, along with the iron, I learned, was binding with the soaps and creating a soap curd which clung to my skin and created that nasty sticky feeling after showering. A water softener to get rid of the hardness along with a prefilter ahead of it to trap the red iron and sediment was the cure. I was now able to enjoy my showers and guess what, I could even use that moisturizing soap and realized that the advertisement was not what was bogus it was my water quality!

Now as a mature adult, I’ve come full circle and once again live in the old family home in the village which is now considered a “city” as the population has grown to a whopping 5,000 people! When I first moved back there was an issue with the water meter. The city water department sent a technician to check it out. While he was working on the meter I told him how disgusting I found the water in our village to be. He was surprised and a little shocked.  He informed me that most people felt the water in our village was great.  I am not sure he understood the difference between people thinking the water was great and people not realizing how much better it could be. I’ll admit it …. I am now a water snob after becoming accustomed to dechlorinated - iron free - soft water thanks to my Kinetico equipment. It happens to the best of us. Once you have water without chlorine, minerals, iron and odor, it is difficult to go back to what you previously thought was “great” water.

 

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