Water softener regeneration is the process through which the water softener flushes out the minerals it catches from the hard water, so it can continue to soften new water as it comes through. When hard water passes through your water softener, ions of calcium and magnesium in the water are replaced with sodium ions. This process takes place in the resin bed. For this system to be effective, your water softener needs to cleanse the resin bed of the harsh minerals when it becomes saturated.
How does water softener regeneration work?
The regeneration is the most technical part of the water softener. Once the resin has trapped all the hardness minerals it possibly can, a salt water solution (brine) needs to flush through the system to clean it out.
The regeneration involves the water softener being flushed for 10 minutes using the block salt that is loaded into the machine. Each cylinder is cleaned one at a time to ensure softened water is provided to your home, uninterrupted. Hard water will never enter your system.
The water is used to drive the brine (salt solution) regenerant through the water softener and then flush it ready for the next service cycle. The number of litres used for each regeneration is dictated by the design of the water softener, its size, and efficiency.
Regeneration and block salt
The water softener needs a specific amount of salt to complete the regeneration. For example, the HV3 needs 300 grams of salt for each regeneration. The brine solution in the bottom of the cabinet is saturated with salt. 300 grams of salt requires 0.8 litres of water, this dissolves the salt and holds it in solution. So, 0.8 litres of water is used for the concentrated brine per regeneration.
This concentrated brine is diluted with more water as it is injected into the water softener during regeneration. In fact, the brine injector works on the venturi principle; as water goes through the injector it creates a vacuum. This then sucks the brine into the injector as it passes into the water softener.
The amount of water needed to draw the brine from the brine tank through the injector, and then to the resin bed, is known as the ‘motive’ water.
How much water is needed for regeneration?
The volume of motive water needed is 3 times the volume of the concentrated brine, so the total volume of brine and motive water for the HV3 is 3.2 litres per regeneration. This dictates the first volume of water.
The second volume of water required is to rinse the spent brine (or what is now calcium chloride solution) from the resin bed and wash it down the drain.
This typically requires 2 ‘bed volumes’ (a bed volume is the volume of the resin tank) to rinse thoroughly. For the Harvey Water Softener, the rinse volume is 13.8 litres – so the total regeneration water requirement is 17 litres.
Modern water softeners, like ours, are very water efficient; typically using less than 2% of the volume of softened water produced between regenerations. This is partially because we do not incorporate a ‘backwash’. This is something typically done in America where there is relatively poor quality water, so the resin bed requires cleaning on a periodic basis - which is not required in the UK.