Spacing of pipe supports – how to properly position the fastening

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Spacing of pipe supports – how to correctly place the fastening

Every plumber who has been doing heating or water distribution for more than a few seasons will tell you that pipe supports are one of those things that are neglected until something goes wrong. The pipe bends, makes clattering noises during flow, or in the worst case, becomes loose from the route and starts moving with every heating cycle. All these problems have a common denominator: incorrect spacing of the fastening. Not an expensive support, not poor pipe material – simply supports placed too far from each other, or on the contrary, chaotically placed without any logic.

In this article, we will look at the topic of support spacing systematically – from the physical principles behind the recommendations, through specific spacing tables for different types and diameters of pipe, to practical situations from installation practice, where standard recommendations are not enough and you need to think more deeply.

Why spacing matters – the physics behind the numbers

A pipe is essentially a beam supported at points. Between two supports, it hangs in the air – and this unsupported part behaves exactly as predicted by material mechanics. The self-weight of the pipe (plus the weight of the medium, i.e., water or antifreeze) creates a bending moment that is proportional to the square of the length of the unsupported section. Simplified: if you double the spacing of the supports, the deflection does not increase twice, but four times. That is why the consequences of too large spacing are so significant.

Plastic pipes – and this applies especially to systems like Hepworth, where PE-X, PP-R or PB pipes are used – have one additional property that metal pipes do not have to a significant extent: material creep. Plastic slowly changes shape under long-term load, even if the stress is well below the immediate strength. A support placed too far away may not cause an immediate problem – the pipe bends gradually, over months or years. When the customer notices it, the installation may already be behind plaster or under the floor.

Another factor is thermal expansion. Plastic pipe expands significantly more when heated to operating temperature than copper or steel. Supports must allow this movement (or control it), and their spacing directly determines how much force will be generated at the fixed points of the system during temperature change.

From the graph, it is clearly visible why plumbers who underestimate the frequency of supports run into problems precisely with plastic pipe systems: the deflection curve is steeper than most people intuitively expect.

Standard recommended spacings – tabular overview

Recommended spacings of supports are based on normative requirements (e.g., European standards for water and heating installations), recommendations from pipe system manufacturers, and long-term plumbing practice. The values vary according to:

pipe material (PE-X, PP-R, PB, PVC, copper, steel)
external diameter of the pipe
operating temperature of the medium
direction of installation (horizontal vs. vertical pipe)

For plastic pipes used in Hepworth systems (PE-X, multi-layer PERT/AL/PERT and similar), the following approximate values apply for normal heating (operating temperature 40–70 °C):

External diameter of the pipe	Horizontal – cold water / heating	Vertical (risers)	Medium temperature above 60 °C
15 mm (e.g. 15×2)	500 – 600 mm	800 – 1000 mm	400 – 500 mm
18 mm (e.g. 18×2)	600 – 750 mm	1000 – 1200 mm	500 – 600 mm
22 mm (e.g. 22×3)	750 – 900 mm	1200 – 1500 mm	600 – 750 mm
28 mm (e.g. 28×3)	900 – 1100 mm	1500 – 1800 mm	750 – 900 mm
32 mm and above	1000 – 1200 mm	1800 – 2000 mm	800 – 1000 mm

Important note: The values in the table are approximate maximum values for a straight section without loaded fittings. Where a valve, fitting or other heavier element is mounted on the pipe, a support must be placed immediately next to this element – regardless of the overall spacing in that section.

Horizontal vs. vertical installation – a fundamental difference

One of the most common mistakes I see when assessing existing pipe systems is that the plumber applies the same spacing for horizontal and vertical sections. These two situations differ fundamentally from a physical point of view.

With horizontal pipe, the weight of the pipe and the medium acts perpendicular to the axis of the pipe. Each unsupported section therefore "hangs" and tends to bend downward. The longer the unsupported section, the greater the deflection – and with plastic pipe filled with gas (air during pressure testing), the weight is low, but with water filling, it increases significantly. Therefore, shorter spacing is required for horizontal sections.

With vertical risers, gravity acts along the axis of the pipe. The pipe does not try to bend, but rather to compress or, in the case of insufficient support, to slide downward. Here, supports serve the function of capturing longitudinal forces and preventing displacement. Since the deflection is significantly smaller, we can allow for larger spacing – typically 1.5- to 2-times the spacing of horizontal sections of the same diameter.

Special rules – where a support must always be installed regardless of spacing

Along with the regular spacing of supports, there are specific locations where a support must always be installed – regardless of the distance from the previous one:

On each side of a bend or elbow – when the direction of the pipe changes, axial forces arise that would otherwise transfer the load to the entire section without a nearby support
Immediately before and after each fitting – valves, ball valves, filters, and similar components are heavy and change the direction of forces; the distance from the support to the fitting should not exceed 100–150 mm
On each side of a tee (T-piece, reducer) – branches create complex force patterns and require stabilization from both sides
At the entry and exit from masonry or structure – pipe passing through a wall must be secured immediately after exiting to prevent movement from being transferred to the protective sleeve
At each measuring point – thermometers, pressure gauges, flow sensors must be mechanically stable
At the beginning and end of each straight section – the transition into an expansion bend or expansion loop requires a fixed point

Fixed points vs. sliding points – a key distinction for plastic pipes

This is a topic where even experienced plumbers sometimes hesitate. With plastic pipe, thermal expansion is so significant that it cannot be ignored. The thermal expansion coefficient for PE-X is approximately 0.15–0.20 mm per meter and degree Celsius. For 10 meters of pipe and a temperature change of 50 °C (cold water 20 °C → heating 70 °C), this means an elongation of 75–100 mm. If we were to prevent this elongation, enormous stresses would develop in the pipe.

Supports must therefore be designed as:

Fixed points (fixed anchors) – the support holds the pipe firmly, preventing movement in both the axial and radial directions. Double plastic anchors, such as Double Anchor 601007H or Double Anchor 601008H, are typically designed to secure the pipe firmly in both axes after tightening.
Sliding points (guiding supports) – the support prevents lateral movement and bending, but allows axial sliding of the pipe during thermal expansion. Simple anchors – for example Simple Anchor 601004H, Simple Anchor 601005H, or Simple Anchor 601006H – are often intended precisely for sliding points, where lateral stability is needed without blocking longitudinal movement.

On each straight section of plastic pipe, fixed points must be placed in such a way that the elongation due to thermal expansion is directed into pre-designed expansion bends or compensators. The spacing between fixed points depends on the length of the expansion loop and the allowable elongation. Between two fixed points, there can be several sliding supports in the standard grid.

For more information on choosing between simple and double anchors, see the article Simple Anchor vs. Double Anchor – when to use which in this Knowledge Center.

Effect of temperature on recommended spacing – why heating requires tighter fastening

Many plumbers rely on experience with cold water distribution and apply the same spacing to heating systems. This is a mistake. Plastic materials lose some of their rigidity at higher temperatures – technically known as a drop in the modulus of elasticity. The consequence is simple: with the same spacing of supports, the pipe filled with hot water will be more prone to sagging than the same pipe filled with cold water.

For PE-X pipe, approximately:

at 20 °C: full rigidity, spacing according to standard tables
at 40 °C: modulus of elasticity drops to about 80 % of the value at 20 °C → reduce spacing by 10–15 %
at 60 °C: modulus of elasticity about 60 % → reduce spacing by 20–25 %
at 80 °C (maximum operating temperature for some PE-X): modulus of elasticity below 50 % → reduce spacing by 30 % or more

In practice, this means that for PE-X heating systems with temperatures above 60 °C, always use a reduced set of recommended spacing. Some pipe manufacturers provide their own correction tables directly in the technical documentation – it is good to check them when working with a specific product line.

Practical scenarios from installation practice

Scenario 1: Heating distribution in a suspended ceiling

A typical situation in new buildings: horizontal heating lines run under the ceiling of the living floor, cut into drywall. PE-X pipe 18×2 mm, medium temperature 55/45 °C. The plumber is tempted to place supports every meter, as they are easily hidden in the ceiling. Mistake. For 18 mm PE-X at operating temperature of 55 °C, the recommended maximum spacing is 600 mm. Once the ceiling is closed and the pipe is heated, insufficient fastening will cause visible sagging and noise during flow – the customer will hear it in the bedroom right after the first boiler start-up.

Correct procedure: supports every 500–600 mm, before and after each fitting, before each T-piece. If the route changes direction, the coleno must be fastened within 100 mm from the center of the bend on both sides.

Scenario 2: Vertical riser in an apartment building

Vertical PP-R 25×4,2 mm riser, five floors, each floor 2.8 m. Total height 14 meters. Medium: heating 70/50 °C. Thermal expansion: approx. 0.15 mm/(m·K) × 14 m × 50 K = 105 mm. This is more than 10 cm of elongation when filled with hot water. The riser must have well-designed fixed points (typically one per floor near the branch to the apartment distribution) and sliding supports in between. Spacing of sliding supports for PP-R 25 mm at this temperature: approx. 800–900 mm.

Scenario 3: Boiler room – short, densely connected lines

In a boiler room, the lines are short but full of valves, pumps, distributors, and others. Here, spacing tables are almost insufficient – fastening is dictated by the position of the fittings. Each valve, each pump, each distributor needs a support within 100–150 mm. The distances between these supports may be larger, but in practice, this results in a support every 300–400 mm, as the fittings are close together.

Scenario 4: Floor heating – distributor and supply lines

From the floor heating distributor, PE-X 16×2 mm tubes go down or sideways to the floor slab. These sections are short – usually 0.3–1.0 m – and quickly disappear under the floor construction. Despite this, each supply line at the distributor must be fastened, otherwise the flow of heated medium when the system starts up will cause slight waviness in the route and repeated heating and cooling may cause material fatigue at the point where the tube bends when exiting the distributor.

Most common mistakes in support placement

From dozens of inspected installations, the following typical mistakes emerge:

Too large spacing on horizontal sections – the result is visible sagging of the pipe, noise during flow, an aesthetic problem in the basement or boiler room
Ignoring fittings and fittings – a valve or T-piece without a nearby support is permanently exposed to bending stress and may crack the joint after prolonged operation
Using fixed supports along the entire route without expansion loops – the pipe has nowhere to expand, stresses increase, joints and fittings are mechanically overloaded
Same spacing for heating and cold water – heating requires tighter fastening
Supports placed only where it is convenient – supports are omitted in corners, behind pipes, in tight spaces, precisely where they are needed
Mixing sliding and fixed points – using a double rigid support instead of a sliding one at a point where the pipe should move creates axial stresses

More about problems related to poor choice or installation of supports can be found in the article Common problems with plastic supports – cracking, loosening, inappropriate size.

Choosing the correct type of support for a given section of the route

Spacing of supports cannot be addressed separately from the choice of their type. For a straight section with sliding points, a simple clamp is suitable – it holds the pipe in the transverse direction, but with proper setting allows axial movement. For fixed points of the route, a fixed fixation in both directions is required, i.e., a double clamp.

If you are unsure which type of support is suitable for your specific case, read the article How to choose the right plastic support for the pipe – simple vs. double in this Knowledge Center. You will also find there an overview of dimensional compatibility for different pipe diameters – which is closely related to the correct selection of a specific clamp from the range, where dimensions cover the most popular sizes used in Hepworth systems.

Practical tips for planning fastening before installation

The best time to plan fastening is even before the first piece of pipe enters the construction site. Here is a procedure that works:

Draw the route on the plan – even a rough sketch with bends, T-joints, valves and places where the pipe crosses a structure.
Mark the required fastening points – every valve, every bend, every T-joint, every structural crossing.
Between required points, distribute regular sliding fasteners – according to the spacing table for the given diameter and medium temperature.
Check whether you have designed fixed points and expansion loops – where the route runs more than 5–6 meters without a change of direction.
Count the number of pieces – how many single and how many double clamps you need, and what diameters.

This procedure significantly reduces the likelihood that you will miss a fastening point on the site. If you want to go into more depth for a specific installation, read the article Installation of plastic pipe fasteners step by step.

Most frequently asked questions (FAQ)

Can I use the same fastener spacing for heating pipes as for cold water?

No, you cannot. Plastic pipe becomes softer at higher temperatures and is more prone to sagging. For heating systems with a medium temperature of 55–70 °C, reduce the recommended spacing by 20–30 % compared to cold water systems of the same diameter. For example, where 750 mm would be sufficient for cold water, use 500–600 mm for heating.

What happens if I place fasteners too far apart?

In the short term, the pipe will visibly sag and will knock when flowing, as the medium hits the sagging section. In the long term, the plastic material under constant bending load "creeps" – it deforms permanently, even if the stress is below the immediate strength limit. This can lead to problems with connections near the deformed section and, in exceptional cases, to cracks in the material after years of operation.

Should I place fasteners in places where the pipe passes through a wall or partition?

Yes, directly before and after each passage through a wall or ceiling. A structural passage is made through a protective sleeve and the pipe must not be fixed inside the sleeve – therefore it must be stabilized by fasteners immediately after exiting both sides. The distance between the fastener and the sleeve should not exceed 100–150 mm.

What is the difference in fastening between single and double clamps in terms of spacing?

The type of clamp does not directly affect the spacing – this depends on the diameter and material of the pipe and the operating temperature. The difference is in the function: a single clamp (e.g. Single Clamp 601005H) typically serves as a sliding point, while a double clamp (e.g. Double Clamp 601008H) serves as a fixed point. Correct placement of fixed and sliding points is just as important as the spacing itself.

How many fasteners do I need per meter of horizontal PE-X 18 mm pipe for heating?

At an operating temperature of around 55–60 °C and a straight section without valves, the recommended spacing is 500–600 mm. This means 2 fasteners per meter – one every 50 cm. In practice, mandatory fasteners near bends and valves are added, so the actual consumption per meter of route can be 20–30 % higher than with a purely regular spacing.

What if the ceiling or wall is made of a material that holds the clamp less well – for example, aerated concrete?

The load-bearing capacity of the clamp in the substrate is a separate topic, but in terms of fastener spacing: if the fastening at a given location is weaker (poor anchoring into the substrate), it is reasonable to slightly reduce the spacing so that the force on each clamp is lower. If you have doubts about the load-bearing capacity, consult the manufacturer of the anchoring material or use expansion anchors and fasteners with a larger contact area. This issue is also related to the choice of fastening system, which is discussed in more detail in the article Fasteners for the Hepworth system – compatibility with plastic pipe.

Conclusion – spacing is not a coincidence, it is a calculation

Correct placement of fasteners is not a matter of intuition or habit from a previous project. It is a matter of specific numbers: pipe diameter, operating temperature, laying direction, position of valves, and the distinction between fixed and sliding points. When you know these parameters and apply them systematically even before the installation begins, you will save yourself from problems that the customer will encounter after five years – and by then the pipe will be behind the plaster.

Hepworth plastic pipes are long-lasting and reliable – provided their installation corresponds to their properties. And the key property of plastic pipes is thermal expansion combined with reduced stiffness at higher temperatures. Both of these phenomena require a more thorough approach to fastening than we are used to from working with copper or steel pipes. Correctly chosen and correctly placed fasteners – both single and double clamps from proven product ranges – are the investment that always pays off.

Do you have a question about this topic?

Not sure or dealing with a specific situation in your home? Write to us – we are happy to help.