Phosphonate water treatment chemicals

6% on phosphonates

Read from the UK Trade Tariff on 26 September 2026, organo-phosphorus compounds of heading 2931 carried 6% duty on goods from China: etidronic acid (HEDP) and its salts, the amino phosphonates ATMP, EDTMP, DTPMP and their relatives, which have their own line, and other phosphonic acids. HEDP and the residual lines have a 0% rate only for listed pharmaceutical substances declared with additional code 2500, and the biocide THPS (bis[tetrakis(hydroxymethyl)phosphonium] sulphate) has a 0% suspension from 5 August 2026 on the residual line. There was no anti-dumping measure.

Formulated water treatment blends that mix phosphonates with polymers, biocides or corrosion inhibitors are preparations classified elsewhere, so confirm the commodity code from the composition. Our cleaning products guide covers detergents that use these chemicals.

REACH, CLP and drinking water

Each phosphonate imported at one tonne or more a year needs UK REACH registration or a valid transitional notification, and acid forms are corrosive, so drums and IBCs need GB CLP labels, an English safety data sheet and UN-approved packaging. Detergent makers should check the phosphorus limits for consumer laundry and dishwasher detergents before reformulating.

Chemicals added to public water supplies in England must be approved under regulation 31 of the Water Supply (Water Quality) Regulations 2016 and are usually specified to the relevant BS EN standard for drinking water treatment chemicals. Industrial cooling water and boiler use does not need that approval but still needs the chemical paperwork.

Worked duty example

An invented example rather than a quote: 40 tonnes of ATMP solution in IBCs, commodity code 2931 49 40 00, bought for £36,000 free on board, with £4,000 of freight and insurance, so £40,000 is the value customs works from. Duty at the 6% rate for phosphonate scale inhibitors is £2,400. VAT at 20% applies to £42,400, so £8,480. A VAT-registered buyer usually recovers the VAT, so the border adds £2,400 to the landed cost. The same value of HEDP under 2931 49 30 00 would also pay 6% unless it is a listed pharmaceutical substance declared with additional code 2500. See calculating UK import duty and VAT for the method.

What goes wrong

Phosphonates are sold by active content, and that is where lots fall short. A 50% ATMP solution arrives at a lower active content, phosphorous acid and orthophosphate impurities are high, chloride or iron exceeds the limit for sensitive systems, and colour varies between lots. IBCs leak or freeze in transit, and labels and safety data sheets do not match GB CLP.

Test each lot for active content by titration, phosphite and phosphate by ion chromatography, chloride and iron, pH and density against the specification, check calcium carbonate inhibition in a simple jar test against a retained sample, and inspect IBCs, UN markings and labels before loading.

Cambridge China Bridge sources HEDP, ATMP and other phosphonates for water treatment formulators and detergent makers, with active content testing agreed in the contract. Replacing an existing supplier? See our second-supplier service.