Water Transfer Systems

Water transfer is a primary factory application — from municipal supply to industrial raw-water lines. This guide covers engineering considerations; pipe specifications and quotes are on the HDPE water pipe product page.

Where PE sits in a water network

In potable water systems, polyethylene pipe serves both the transmission main from source or reservoir to the town inlet and the distribution network down to the service connection. The governing product standard in Iran is INSO 14427-2, which fixes material, dimensions and the potable-contact requirements. That hygiene requirement is what separates a drinking water line from a raw water line — not anything visible about the pipe.

Diameter comes from flow; pressure class comes from the hydraulic grade line

These are independent choices, and swapping them is the most common ordering mistake. Diameter follows from design flow and permissible velocity — roughly 0.5 to 2.5 m/s. Below that band suspended solids settle out; above it head loss, pumping energy and surge risk all climb. Pressure class, by contrast, comes from the maximum static head at the lowest point on the line plus a surge allowance — not from the pump's normal discharge pressure.

If the line runs above 20 °C — laid on the surface, in direct sun, or carrying warm water — the PN figure has to be derated and the design basis becomes MOP, not the PN printed on the pipe.

Which joint, where

• Butt fusion: the primary method on transmission mains in medium and large diameters, with qualified equipment and an approved procedure
• Electrofusion: where there is no room for a butt machine — repairs, saddle branches, joints made in an open trench
• Flange and stub end: at valves, pump houses and anywhere the line must be opened later
• Mechanical couplers: mainly small diameters in the distribution network and service connections

Thrust blocks: the part that is specific to a fused line

In steel or ductile iron pipe with mechanical joints, every bend and tee needs a concrete thrust block so that the unbalanced force does not pull the joint apart. A fully fused PE line is one continuous, end-restrained element, and that force is carried in the wall instead. But the exemption applies only to the fused portion: wherever a flanged or mechanical joint enters — a valve, a pump, a transition to metallic pipe — restraint has to be designed.

Handover: the pressure test

The line is hydrostatically tested before commissioning. The part specific to polyethylene is that the pipe expands slightly under pressure — it is viscoelastic — so a pressure drop in the first minutes of the test does not by itself mean a leak. PE test procedures therefore include an initial relaxation phase, and the test has to follow the project procedure rather than the acceptance criteria used for metallic pipe.

Design considerations

• Operating pressure and SDR aligned with hydraulic design
• Fusion joints and leak control on long runs
• Air release valves on profiles with elevation change
• Temperature derating for exposed or high-temperature service