Private water supply filtration calculator
Enter the results from your private water supply analysis to plan your filtration: the calculator shows the sequence of filters, softening, UV and reverse osmosis your water needs, with flows, regeneration water and running costs. Your water is compared with the Private Water Supplies (England) Regulations 2016 — iron 200 µg/l, manganese 50 µg/l, sodium 200 mg/l [1].
Updated 2026-10-24 · every regulation and price links to its source at the bottom of the page. A guide, not a construction design.
Plan the treatment for your supply
Key parameters are marked with a dot. UK reports often give iron and manganese in µg/l, hardness in mg/l as CaCO₃ and conductivity in µS/cm instead of TDS — pick the unit next to each field. An empty field means «not measured», not zero.
Size whole-house reverse osmosis →
In the app, with the same data
The result above is yours, free and without signing in. In the app the same data gives you more:
- Water treatment from your test inside your house plan — the same treatment chain
- See your house in 3D — outside with the roof, inside and as a walk-through
- The plan as PDF and DXF to show a builder or an architect
No retyping: the values from this page are put into a new plan.
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What you typed stays in your browser until you move it into a plan yourself.
How does the calculator choose?
Order. A sediment filter first [2], then iron and manganese removal, carbon, the softener, and UV last on clear treated water [3].
UV for bacteria. The DWI treatment guide takes a dose of about 40 mJ/cm² on water already low in iron and manganese, with an intensity sensor and an alarm [3]; E. coli and enterococci must be 0 in 100 ml [4].
Limits. Chloride and sulphate 250 mg/l and conductivity 2500 µS/cm are indicator values — a signal to investigate [5]; the UK has no hardness standard [6].
Frequently asked questions
Will an RO system remove bacteria from my borehole water?
Do not rely on it: reverse osmosis is for dissolved salts and sends 20–30 % of the incoming water to waste [7]. For bacteria on a private supply the DWI guide uses UV disinfection at about 40 mJ/cm² on clear, pre-filtered water [3].
Is there a hardness limit for drinking water in the UK?
No — there is no hardness, calcium or magnesium standard; a softener is a matter of scale and comfort [6].
What iron and manganese levels need treatment?
Above 200 µg/l iron or 50 µg/l manganese — the values of the Private Water Supplies (England) Regulations 2016 [1].
Sources
- The Private Water Supplies (England) Regulations 2016 (SI 2016/618), Schedule 1, Part 1, Table B, Part II (national requirements) (UK) · regulation · checked 2026-09-29 · source
- dvgw.de, Mechanisch wirkende Filter (DE) · regulation · checked 2026-09-29 · source
- Drinking Water Inspectorate — Private water supplies: treatment guide, UV disinfection, UV disinfection (UK) · recommendation · checked 2026-09-29 · source
- The Private Water Supplies (England) Regulations 2016 (SI 2016/618), Schedule 1, Part 1, Tables A–B; reg. 4(c); Table D (UK) · regulation · checked 2026-09-29 · source
- The Private Water Supplies (England) Regulations 2016 (SI 2016/618), Schedule 1, Part 2, Table C (indicator parameters) (UK) · regulation · checked 2026-09-29 · source
- Drinking Water Inspectorate — Private water supplies treatment guide: The physical and chemical properties of water, Hardness, Table 1 (UK) · recommendation · checked 2026-09-29 · source
- Drinking Water Inspectorate — Domestic water filters and softeners, Reverse osmosis systems (UK) · recommendation · checked 2026-09-29 · source