Water Usage for Backwash

"How much water will the softener use during its backwash cycle"?

We get asked that question all of the time. There is no simple answer. There are a few factors to consider:

1.) System Size - The size of your system will make a great deal of difference. With Fleck brand water softener control valves there are 5 stages of regeneration. Your resin tank's size will dictate the amount of water that goes through it.

2.) Backwash Flow Rate - This factor is a bit hard to determine. Backwash and brining flow rates are listed for various models of Autotrol, Clack and Fleck control valves but they are the maximum flow rate for that particular make and model, not the continuous flow rate of a particular control valve mounted on a particular size mineral tank.

3.) Backwash Time - With many models of softener control valves, the backwash rate and times are adjustable.

As you can imagine, it's pretty tough to answer what appears to be a simple and reasonable question. I had one guy call quite upset about the water he was going to use with his new softener. The spec. sheet called for a 13 gallon-per-minute flow rate during backwash and this softener performed a 180 minute backwash cycle so he deduced that he's going to go through 2340 gallons of water every time his system backwashed! That's not the way it works.

Let us use the Fleck model 9000 as an example. The regeneration time on a model 9000 using a 1/30 rpm motor is 164 minutes. The first stage of the 5 stages the model 9000 uses is the BACKWASH stage. It basically runs the water backwards through the distributor tube and back up through the resin media bed. This process "unpacks" the media bed and loosens any debris trapped inside the bed. This stage will fill the resin tank. Determine the amount of water in your particular media tank and you'll be able to compute the amount of water you will use during the entire regeneration process. Be sure to subtract the volume of the media itself, in this case 1 cubic foot.

Once this cycle is complete the water in the resin tank is flushed out the drain line and replaced with brine. The BRINING cycle does just what you'd think. It draws the brine water from your brine tank into the mineral tank. It does this by virtue of "cavitation": Running regular water past the brine injector thus drawing the brine up through the air-check in the brine tank and up the brine line, through the injector and into the media tank. Once the brine is drawn out of the brine tank, the air-check closes and the process stops. The brine then saturates the media bed in your media tank and exchanges ion charges with the resin beads which then release the calcium and deposits (the hardness).

When this timed process is complete, the brine remains in the tank and water is introduced inside the mineral tank for the SLOW RINSE cycle. The slow rinse cycle is just like it sounds; it slowly rinses the contents of your media tank so that the brine is efficiently passed across all surfaces of your resin media to insure complete release of hardness from the resin beads. Upon completion of this cycle, water is rapidly introduced to flush out the brine and slow rinse water to be replaced by:

The RAPID RINSE water. Just as it sounds, the rapid rinse cycle flushes water in the proper direction down through the media bed and up through the basket at the bottom of your distributor. This water flushes directly out of the drain line and is a timed cycle.

Finally, there is the BRINE TANK FILL cycle. Just like it sounds, this cycle refills the brine tank. The amount of water put into the brine tank depends on your pounds of salt setting. In the case of our Fleck 9000 we will be putting about 7 gallons into the brine tank. The water then sits at the bottom of the brine tank, absorbs salt until it becomes saturated and waits for the next time your softener calls for regeneration.

Tank sizes vary, salt settings are adjustable, control valve makes and models are all different with different capacities so you can see now why it is difficult to answer the question "How much water will my softener use during regeneration"? As a rule-of-thumb I tell people "the volume of your mineral tank times 3 plus the amount of water used during the rapid rinse cycle plus about 7 gallons for the brine tank". Keep in mind that different sized brine tanks will require different amounts of water. Also, varying salt requirements will change the water volume in the brine tank as well, but it gives people a good idea of what kind of volume of water to expect out of the softener's drain line.