Water Softener Buying Guide: 10 Things to Check Before You Buy

The hardness of your supply determines what size softener you need and how much salt it will use. Free test kits are available from most softener suppliers. Alternatively, enter your postcode on your water company's website for a hardness reading in parts per million (ppm) or milligrams per litre (mg/L). Typical very hard areas in the south east register 300 to 400 ppm. The hardness figure feeds directly into sizing calculations.

An undersized softener regenerates too frequently, wastes salt, and may not keep up with peak demand. An oversized one regenerates too infrequently, which can allow bacteria to develop in stagnant brine. Size is calculated from: daily water consumption (roughly 150 litres per person), water hardness, and resin capacity. A supplier who quotes without asking about household size and hardness is not sizing correctly.

Salt is the main ongoing expense. A properly sized softener for a family of four in a hard water area typically uses 3 to 5kg of salt per week — around £100 to £200 per year at current salt prices. Add electricity (for timer-based models, around £15 to £20 per year) and the annual service (£80 to £150). Total annual running cost: typically £200 to £370. Ask suppliers for a specific estimate based on your hardness and household size, not a vague range.

Standard warranties range from 1 to 10 years depending on the brand and component. Harvey offers a 2-year standard warranty. Kinetico's non-electric systems come with a 10-year parts warranty. Check specifically: are parts and labour both covered? Is the control valve included? Is annual servicing required to maintain warranty validity? Get the warranty document in writing before signing anything.

UK water regulations require at least one unsoftened cold mains tap for drinking. This is typically the kitchen cold tap. Confirm the installation includes either keeping this tap on the unsoftened supply or installing a dedicated hard water drinking tap. An installation that softens the drinking supply without providing an alternative is non-compliant.

What happens when the softener needs a service or breaks down? Is there a nationwide service network or a single local engineer? What is the response time for a breakdown call? Is a 24-hour helpline available? For a product running continuously for 10 to 20 years, aftercare quality matters as much as the product itself.

Prices for comparable systems vary significantly between suppliers. Getting three quotes for the same type of installation is the most effective way to establish fair market price and creates leverage for negotiation. A supplier who prices fairly should have no objection to you comparing quotes.

If you or anyone in the household has a chronic illness or disability, you may qualify for zero VAT on the purchase. This is not automatic — you must declare eligibility at the time of purchase. On a £1,200 installation, zero VAT saves £200. Ask every supplier explicitly about this before the quote is finalised.