Water Treatment Glossary

Brine is the concentrated saltwater solution a softener uses during regeneration. It restores the resin’s ability to remove hardness minerals; it is separate from the softened water supplied to your taps.

Keeping the correct salt in the salt compartment allows the system to make the brine it needs.

A bypass valve, or bypass valve arrangement, lets water flow around a softener instead of through it. This allows the unit to be isolated for maintenance while maintaining a water supply to the property.

When the softener is bypassed, the water taking that route is unsoftened. The bypass arrangement is one of the details to check when planning an installation.

Calcium and magnesium are naturally occurring minerals that dissolve into water as it passes through rocks and soil. They are the main minerals responsible for water hardness.

An ion exchange softener removes these hardness ions. A standard activated carbon filter does a different job, so a product described as a water filter should not automatically be assumed to soften water.

Flow rate is the volume of water passing through a system over time, usually shown as litres per minute (L/min). A softener’s service flow rate describes its treatment performance during normal use.

When comparing models, consider the demand from taps, showers and appliances running together. Check the stated flow rate and its pressure conditions, rather than choosing by cabinet size alone.

Ion exchange is the process most domestic water softeners use to remove hardness. Resin beads capture dissolved calcium and magnesium ions and exchange them for sodium ions.

This reduces hardness, but does not make the water mineral free. Softening is a different process from filtration for chlorine, sediment or other contaminants.

Limescale is the hard, chalky deposit associated with hard water, often seen in kettles, around taps and on shower fittings. It forms when hardness minerals come out of solution, particularly as water is heated.

A correctly selected and operating softener helps prevent new hardness scale forming in the softened water supply. Cleaning existing deposits is a separate task.

Metered regeneration uses the amount of water that has passed through the softener to control when it regenerates, rather than relying only on a fixed timer.

Depending on the model, regeneration starts or is scheduled when the calculated softening capacity is running low. Correct hardness settings help the system work out how much water it can soften between cycles.

A non electric water softener uses the incoming water’s pressure to operate its controls, without a mains electricity connection.

It still needs the correct salt and suitable drainage. “Non electric” describes how the controls are powered; it does not tell you whether the system has one resin tank or two.

Regeneration restores the softening resin after it has collected hardness minerals. The system uses brine to release the captured calcium and magnesium, then rinses the resin ready for reuse.

The process uses salt and water and discharges wastewater to a drain. How often it happens depends on water hardness, usage, capacity and the model’s controls.

Resin is the material inside a softener’s treatment vessel that removes calcium and magnesium through ion exchange. It consists of small beads that capture hardness ions as water passes through.

Resin needs regular regeneration to keep softening effectively. It is different from a disposable filter cartridge and is not normally replaced whenever you refill the salt.

Softener salt is used to make the brine that regenerates a water softener’s resin. Common domestic formats include block salt and tablet salt.

Use the format and grade specified by the manufacturer. Do not assume every softener accepts both formats, and do not substitute ordinary table salt.

Softening capacity is the amount of hardness a softener can remove before its resin needs regeneration. It affects how much water the system can soften between cycles.

At a higher incoming hardness, the same system generally treats fewer litres before regenerating. Resin volume and salt-storage capacity are different measurements, so check the stated treatment capacity at your water hardness.

A twin-tank softener has two resin vessels. In an alternating twin-tank system, one vessel supplies softened water while the other regenerates or waits to take over.

“Twin-tank” refers to the resin vessels, not a resin tank plus a salt compartment. It describes the tank arrangement, while “non-electric” describes how the controls are powered.

Water hardness measures the dissolved calcium and magnesium in water. UK hardness reports commonly express it as milligrams per litre of calcium carbonate equivalent, written as mg/L as CaCO₃.

Ask your water supplier for a local figure, or use an appropriate hardness test, before choosing a softener or setting its controls. Check which units are used on the report or test.

Water pressure is the force driving water through your pipework, usually measured in bar. It is different from flow rate, which measures the volume of water delivered over time.

Every softener has a specified operating pressure range. Check the supply pressure and the model’s requirements when planning an installation; a high advertised flow rate alone does not establish compatibility.