KAN-therm Push expansion loop

KAN-therm Push expansion loop

A KAN-therm Push expansion loop takes up thermal growth of PEX-c and PE-RT pipe on exposed heating and domestic hot-water runs. Polyethylene in this system moves more than metal, so a straight length between fixed points shifts every time the line heats up. If that movement has nowhere to go, the load transfers into elbows, tees and clips. The loop is used where a change of direction does not give a long enough arm, and the shaft has room to offset the pipe axis.

Main compensation layouts for the Push system

A U-loop is built from four 90° system elbows and pipe lengths of the same diameter. The side arms absorb elongation by flexing, and the axis returns to the same line after the loop. It suits a riser or a header that must stay on one alignment. The best place is the middle of the section between fixed points. If the two sides are unequal, size the arm from the longer one.

An L-shaped compensation arm is a change of direction, not a factory-made part. The length Ls after the elbow takes the stress. Use it at a corner, where a riser turns into a branch, or where the niche cannot hold a full loop.

A Z-offset shifts the axis in parallel. The design length is the sum of the two straight runs; elongation and arm length follow from that. It is the layout for passing a column, a duct or a neighbouring pipe.

Push pipe also allows self-compensation, sometimes called rigid fixing: fixed points sit at each branch tee and the riser is split into short lengths, often one floor. A separate loop is then unnecessary, but the arm on the branch still has to be checked.

Materials and construction

The loop is made from system pipe — electron-beam crosslinked PEX-c or PE-RT type II, usually with an EVOH oxygen barrier. The Push range is Ø12–32 mm. Elbows are PPSU or brass. The joint is a brass or PVDF sliding ring, with no rubber seal. PPSU does not corrode in hot water. Brass is used at a threaded transition. A brass ring goes on with the chamfer toward the fitting; a plastic ring is symmetrical.

For these pipes the material constant k is 15, so the arm is shorter than on stiffer systems, but it is the pipe, not the fitting, that flexes. Do not clip the compensation arm.

Where a linear expansion compensator is used

A linear expansion compensator is needed on exposed heating and DHW risers, in shafts and on wall-mounted headers. On a shaft branch the arm protects the tee while the riser moves along its axis. In a screed or under plaster, Push pipe is usually run in a conduit or insulation, and a separate loop is less often required. The system is intended for indoor water supply and heating. Any other medium should be checked against the pipe data sheet.

How to select an expansion loop

Start with the outside diameter. Risers are most often Ø16, Ø20, Ø25 and Ø32. Then take the straight length, the installation temperature and the operating temperature. Arm length follows Ls = k × √(D × ΔL), where D is the outside diameter in millimetres. Ls tables are in the KAN-therm design guide.

Loop width must cover the travel of both arms and the insulation thickness: the sum of both elongations, twice the insulation thickness, and about 150–200 mm spare. The first sliding support goes no closer than Ls from the elbow. Clips do not sit on the fitting. Price depends on diameter, the number of elbows and rings, pipe length, and whether the elbows are brass or PPSU.

Why order from Pipeline Systems of Ukraine

At Pipeline Systems of Ukraine a KAN-therm Push expansion loop can be put together with the pipe, elbows and rings of the required diameter. We can check the support layout and arm length against the design before dispatch. We work with installers and companies, supply wholesale and retail, and deliver across Ukraine. Documents for a specific item can be requested.

Send a request to confirm availability and price for your diameter.

Popular sizes

Common pipe diameters for which a Push loop is assembled:

• Ø16
• Ø20
• Ø25
• Ø32

Confirm availability of elbows, rings and pipe before ordering.

Send a request to confirm availability and price for the set you need. We will check arm length and the elbow kit before the riser is installed.

FAQ

Frequently asked questions about the KAN-therm Push expansion loop

How is a U-loop different from a compensation arm? A U-loop brings the pipe axis back onto the same line and works with two side arms. An L-arm is only a change of direction: one length Ls after the elbow absorbs the growth. Use the loop when the header must stay on one alignment, and the arm when a corner or niche already changes direction.

What is a Push loop made of, if it is not a moulded polypropylene piece? On Push the assembly is built on site: four 90° PPSU or brass elbows, PEX-c or PE-RT pipe lengths, and sliding rings of the same diameter. A moulded socket-weld loop belongs to the PP system and does not replace a Push joint. The ring must match the pipe, or the joint will not seal.

When can a riser do without a separate loop? Push pipe allows rigid fixing: fixed points at each branch tee and short riser sections, often one floor high. Axial travel is then small and a separate loop is not required. The arm on the branch still needs checking so the tee is not loaded in shear.

How is the compensation arm Ls determined? You need outside diameter, straight length, installation temperature and operating temperature. Elongation comes from the pipe expansion coefficient; the arm is Ls = k × √(D × ΔL), with k = 15 for Push. Ready tables are in the KAN-therm design guide. The first sliding support is placed no closer than this length from the elbow.

Can the Push pipe be bent instead of using four elbows? The pipe can be bent within the system minimum radius, but the KAN-therm guide builds a U-compensator from four 90° elbows and pipe lengths. Bending instead of an elbow cuts the number of joints, yet radius and ovality still have to be controlled. In a shaft riser it is safer to keep system elbows and a free arm with no clip on it.