Guide collection
Tools
Free calculators and interactive tools from Tern Water.
3 guides
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Updated 2026
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Independent & free
Tools
UK Water Hardness Checker by Postcode
Free water hardness checker by postcode. Get your supply's hardness in ppm and Clarke/German degrees, the soft to very hard band, and what to do.
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Tools
Water Softener Salt Cost Calculator
Free water softener salt calculator: estimate your annual salt use in kg and the yearly cost of loose salt versus a delivery subscription.
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Tools
Water Softener Sizing & Grain Capacity Calculator
Free water softener sizing calculator: enter occupants, water use and hardness to get your grains-per-day load and the right softener size.
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