InterPlast

InterPlast pipework fittings for pool and spa circuits

Every pool and spa circuit is held together by a handful of small plastic parts: the bends that take the line around an obstacle, the straight couplers that join two lengths of pipe, and the check valve that stops water running back towards the pump when it shuts down. Here you will find InterPlast fittings in the metric sizes most often used in pool and spa plumbing, from slim 25 mm spa lines through to 63 mm suction and return pipework.

What the range covers

The parts listed on this page are the everyday building blocks of a circulation loop rather than specialist items. They cover changes of direction, straight joins between pipe lengths or between pipe and equipment, and non-return protection on the pressure side.

• Elbows: 90° and 45° bends in 25 mm with a female end, for routing spa and small-bore pipework around tight corners or stepping a line gently out of alignment.
• Straight connectors: 25 mm and 40 mm couplers with two female ends, used to join two pipe stubs, extend a run or repair a cut section.
• Check valve: a 63 mm water check valve supplied with union fittings, so it can be fitted into, and later removed from, an existing line without cutting the pipework.

Working out the size you need

Metric PVC pipe is described by its outside diameter, so a 25 mm fitting accepts pipe measuring 25 mm across the outside, not across the bore. Measure the existing pipe with a vernier or a tape across the widest point, and measure in two directions in case the pipe has gone slightly oval. A 40 mm pipe will not enter a 50 mm socket and will sit loose, so there is no scope for making a near-miss work.

• 25 mm: typical of spa and hot tub manifolds, air lines, jet feeds and small top-up or bypass runs.
• 40 mm: common on smaller pools, heat pump and heater connections, and on branches off a larger main.
• 63 mm: used for main suction and return lines on medium and larger pools, where flow has to be carried with little pressure loss.

Also check what the female end actually is before ordering. A plain socket is bonded with PVC solvent cement; a threaded socket takes a male thread sealed with PTFE tape or a thread sealant. The two look similar at a glance but are not interchangeable, so compare the part against the end you are replacing and note whether the inside is smooth or cut with a thread.

Choosing between a 90° and a 45° bend

Every change of direction adds resistance to the circuit, and a filtration system that fights its own pipework runs hotter and filters less. Two 45° elbows used to ease a line around a corner will usually flow better than one sharp 90°, which is worth remembering when reworking an existing run. Keep bends away from the immediate inlet of the pump where possible, as turbulence directly in front of the impeller can cause noise and reduce suction.

A check valve belongs on the pressure side, typically after the pump or before a heater, salt cell or chemical feeder, so that water and treated water cannot drain back when the system stops. Note the flow arrow moulded into the body and fit it pointing in the direction of travel. The union collars on either side make it straightforward to isolate the valve later and inspect the internal flap or disc, which is the part that eventually wears.

Fitting and sealing

Cut pipe square, deburr the cut edge and dry-fit the parts before committing. For solvent-weld joints, clean and prime both surfaces, apply cement to pipe and socket, push home with a quarter turn and hold for a few seconds. Allow the joint to cure before refilling and pressurising the system. On union connections, keep the O-ring clean, lubricate it lightly with silicone grease rather than petroleum-based products, and tighten the collar by hand; over-tightening with tools is the usual cause of cracked union nuts. If a union seal is weeping, measure the old O-ring across its inside diameter and section thickness before ordering a replacement.

InterPlast at PoolParthub.com

Here we stock InterPlast elbows, straight connectors and check valves in 25 mm, 40 mm and 63 mm, listed by size and end type so the right part can be identified from the pipe already in the ground. Each item carries its own reference, which makes repeat ordering simple when a repair calls for several identical couplers or bends.

These are the parts that come up during a leak repair, a heat pump installation or a spa rebuild, and they are needed in a hurry rather than planned for. Keeping a few spare elbows, couplers and O-rings alongside the equipment saves draining a system twice, and the same fittings serve both pool circulation lines and smaller spa pipework.