Blue Tubing 3/8" NSF - Sold by the Metre

Blue polyethylene tubing 3/8" - NSF

Semi-rigid polyethylene tubing, 3/8" (9,52 mm) outside diameter, blue, NSF certified. Supplied on 150 m reels and sold by the metre.

Compatible with all 3/8" push-fit quick-connect fittings, John Guest, DMfit and equivalents.

NSF certification

NSF certification covers materials in contact with water intended for human consumption. It confirms that the tubing releases no undesirable substances into the water passing through it.

On a water treatment installation this is not a detail. The tubing is in permanent contact with the distributed water, often over several metres and for years. Uncertified tubing fitted downstream of an RO system can compromise the very water quality the whole treatment chain was built to deliver.

Why 3/8"

3/8" is the diameter of the installation's flow lines, as opposed to the 1/4" used on service lines.

It is found on the sections where bore directly governs fill time or comfort at the tap: pressure tank outlet, faucet feed, product line of a high-output RO system, connection to an American fridge or an ice machine.

Running one of these sections in 1/4" to save a few euros of tubing means throttling everything downstream of it.

Colour coding

On a multi-line installation, colour serves to identify each circuit at a glance: raw water, treated water, drain, tank return.

Blue is traditionally associated with treated or cold water. What matters is not the convention chosen but its consistency: a colour code held across a whole estate saves time on every service call and prevents connection errors.

Sold by the metre

The reel holds 150 m, but the tubing is billed by the metre. You order exactly the length the job needs, with no leftover reel tying up stock and no unusable offcut.

Fitting

Cut the tube square with a tube cutter. An angled cut, or one crushed with pliers, stops the fitting's O-ring bearing evenly, the first cause of leaks on this type of connection.

Push fully home into the fitting, then pull lightly to check engagement.

Keep a generous bend radius. This matters more in 3/8" than in 1/4": tightly bent tubing goes oval, loses usable bore and fatigues at the bend. And on a flow line, a pinched bore costs litres per minute directly. Where space is tight, use an elbow fitting rather than forcing the tube.

Watch the diameter

3/8" imperial (9,52 mm) and 10 mm metric are close but not interchangeable. Metric tubing is not gripped correctly by the collet of an imperial fitting and leaks under pressure. Check the standard of your fittings before ordering.