How do I look after a water softener, and how much salt does it use?

A water softener is one of the few appliances in a house that has a genuine consumable and almost no other maintenance. It works by passing hard water through a resin bed that exchanges calcium and magnesium for sodium, and periodically it regenerates that resin by flushing it with strong brine made from the salt you add. Everything that goes wrong with a softener is either a salt problem or a blockage in that regeneration cycle, and both are recognisable from the tank without any tools.

What you'll need

• Water softener salt in the form your machine specifies
• A broom handle or similar, for breaking a salt bridge
• A hardness test kit or strips (optional)
• The manufacturer's manual for your model

Step by step

1. Use the salt form your machine actually specifies.Block salt, tablet salt and granular salt are not interchangeable. Block salt suits compact cabinet softeners with small brine chambers; tablet salt suits most full-size units; granular is generally for specific models only. Using the wrong form is a common cause of bridging and of poor regeneration. The manual states it.
2. Keep the salt level above the water in the brine tank.Check monthly. There should always be visible salt standing above the water line. If the salt has dropped below it, the brine is too weak to regenerate the resin properly and the water will start to harden even though the machine is running.
3. Expect a household to use roughly a bag every four to eight weeks.Actual consumption depends on water hardness, occupancy and how much water you use — a hard-water four-person household uses substantially more than a soft-water couple. Rather than guessing, note the date each time you fill it and you will have your own figure within a few months.
4. Check for a salt bridge, which is the classic hidden failure.Humidity and certain salt types can form a hard crust that spans the tank with an air gap underneath. The tank looks full, the salt is not touching the water, no brine is made, and the water hardens with nothing apparently wrong. Push a broom handle gently down through the salt — if it hits a hard layer and then breaks through into a void, that is a bridge. Break it up and remove the crust.
5. Look for salt mush at the bottom of the tank.A sludge of undissolved salt fines can build at the base and block the brine draw. If the machine is using far less salt than usual and the water is hardening, scoop it out. This is the second most common cause after bridging.
6. Clean the brine tank every one to two years.Let the salt run low, siphon or bail out the water, remove the residue, wash the tank with warm soapy water, rinse thoroughly and refill. Check the manual for whether the brine well and float need removing, and never use bleach or a strong cleaner unless the manufacturer specifies it.
7. Test the hardness at a softened tap now and then.Test strips or a simple drop kit, at a bathroom cold tap or a hot tap fed through the softener. Softened water should read close to zero. Doing this two or three times a year finds a failure long before scale reappears in the kettle. Remember the kitchen cold tap should be hard by design.
8. Confirm the kitchen drinking tap is still hard.A softener exchanges calcium for sodium, and the kitchen cold tap should be plumbed before the softener so drinking and cooking water is unaffected. Test it occasionally, especially after any plumbing work, and particularly if anyone in the house is on a low-sodium diet or making up infant feeds.
9. Watch for signs the resin itself is ageing.Resin lasts a long time — often ten to twenty years — but it does degrade, especially where the incoming water carries chlorine or iron. Falling performance despite correct salt levels, a clean tank, and a regeneration that is happening, points at the resin or the valve rather than the salt.
10. Know where the bypass is before you need it.Every installation should have a bypass valve so the house has water while the unit is serviced or if it fails. Find it now and label it. It is also what you use if the softener starts sending salty water into the house, which means a valve fault.
11. Service it on the manufacturer's schedule if it has one.Many units are effectively maintenance-free apart from salt; some specify a periodic check of the valve, the injector and the seals. Follow the manual rather than a general rule, and keep the model number to hand.

Tips

• Keep the salt somewhere dry. Bags stored in a damp garage absorb moisture and are far more likely to bridge once they are in the tank.
• Fill the tank to about two thirds rather than to the brim. A completely full tank bridges more readily and is harder to inspect.
• Note the date on the bag each time you add salt. Within a few months you will know your household's real interval and can buy accordingly.
• If your water tastes salty at any tap, stop using the softened supply for drinking and check the unit — that is a regeneration or valve fault, not normal.
• Descale the kettle and shower head when a new softener goes in. It will not clear years of existing deposit quickly on its own.

Common mistakes

• Topping up salt without checking for a bridge — Adding salt on top of a crust makes the bridge thicker. The tank looks fuller than ever while no brine is being made at all.
• Using the wrong form of salt — Block, tablet and granular salt behave differently in different tank designs. The wrong one dissolves badly, bridges, or leaves mush that blocks the brine draw.
• Letting the salt run out completely and repeatedly — Each time it runs dry the resin is not regenerated and hard water passes through. Repeatedly, it lets scale re-establish in the boiler and cylinder the softener was fitted to protect.
• Softening the kitchen drinking tap — Softened water carries added sodium in place of the calcium removed. The kitchen cold tap should be taken off before the softener, which matters for anyone on a restricted-sodium diet and for making up infant feeds.

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