Sourcing aluminium threaded unions from China

UK duty on aluminium threaded pipe unions

Read from the UK Trade Tariff on 2 October 2026, heading 7609 covers aluminium tube or pipe fittings. Ordinary aluminium threaded pipe unions fall within the other-fittings line, 7609 00 00 90. The table shows union configurations sharing that code, rather than separate tariff subdivisions.

The supplied facts show 4% duty on goods from China across the heading, with no listed anti-dumping or countervailing duties, suspensions or import controls. Confirm the commodity code against the complete product specification. The aluminium pipe fittings guide covers the wider heading.

Confirm with HMRC or your customs broker whether these fittings fall within the aluminium scope of the UK carbon border adjustment mechanism for imports from 1 January 2027. Ask the factory for emissions data when planning future imports and consult the UK CBAM guide.

Specify the pipe threads and union seal

Specify the thread form, pitch, size and tolerance at each pipe connection, including whether the thread is parallel or tapered. Define the union nut thread separately. Supply a drawing showing bore, overall dimensions, sealing face and wrench flats, and approve a sample assembled with your mating fittings.

Agree alloy and temper, seal material, fluid compatibility, working pressure, test pressure, temperature range and finish. State whether sealing uses a gasket, an O-ring or mating metal faces. Ask for material certificates and batch pressure-test reports.

Pressure equipment rules regulate equipment and assemblies with maximum allowable pressure greater than 0.5 bar. Fittings in compressed-air, gas or refrigerant piping can fall within the rules as part of the piping, depending on fluid, pressure and size. Agree the applicable conformity evidence with the system designer before ordering.

Worked duty example

Illustrative example, not a quote: Illustrative order: 8,000 aluminium threaded pipe unions for compressed-air lines under 7609 00 00 90, invoiced at £24,000 free on board, with £1,200 of freight and insurance to the UK. The customs value is £25,200. Duty at 4% is £1,008. Import VAT at 20% is charged on the customs value plus duty, £26,208, so it is £5,241.60. Import taxes total £6,249.60; a VAT-registered importer can usually reclaim the VAT, so the lasting cost is the £1,008 of duty. The import duty and VAT guide explains each step.

Inspection checklist

Threads and fit: gauge the pipe threads and union nut thread, then assemble samples with the approved mating parts. Check for cross-threading, binding and insufficient engagement.

Sealing faces: check alignment, surface damage, gasket seating and seal material. Test assembled samples for leakage at the agreed pressure.

Material and machining: match alloy and temper certificates to the batch. Check bores for burrs, sealing faces for tool marks and cast bodies for porosity.

Arrival and records: check counts, damaged threads, missing nuts and seals, and batch identification against packing records. Use the quality inspection guide to organise the checks.

What goes wrong

A union can screw together yet leak because the sealing faces do not align or the seal material does not suit the fluid. Similar-looking pipe threads can bind or damage the mating fitting. Mixed union halves and nuts can also prevent correct seating.

Softer substituted alloy can strip at the threads, while casting porosity or machining burrs can cause leaks or obstruct the bore. Keep an approved assembled sample and compare production and arrival samples against it, including the seals and material records.

Cambridge China Bridge sources these products for UK businesses, checking the factory and the documents before shipment. See factory verification. For repeat volumes, see container programmes.