Frequently asked questions about plastic pipe clamps and anchors
Frequently asked questions about plastic pipe clamps and anchors
If you are working with plastic piping – whether it is part of a Hepworth system or another installation system – you will sooner or later face the question of fastening. At first glance, it seems to be a trivial matter: a clamp is just a piece of plastic. In practice, however, the situation is different. Choosing the wrong anchor, incorrect spacing, confusing single and double clamps, or underestimating the size – these are mistakes that cost time, money, and in the worst case, cause problems throughout the entire piping system. In this article, we have gathered the most frequently asked questions that customers ask before purchasing, during installation, and after it. The answers are practical, specific, and based on real experience with installations in residential and commercial construction.
What is an "anchor for pipe" and why is it distinguished from a regular clamp?
In everyday language, the words "clamp" and "anchor" are used as synonyms, but in catalogs and technical documentation, they are distinguishable terms. A clamp is a general term for an element that holds the pipe against a wall, ceiling, or structure. An anchor (in the sense of a product line, such as the series 601004H–601008H from Hepworth) is a specific type of clamp designed for fastening polypropylene, PEX, or PB piping to solid substrates via a pin or screw.
This distinction is especially important when ordering: if you are looking for a clamp to firmly fasten to a masonry wall with a recess, you are talking about an anchor. If you are looking for a free-moving clip that allows expansion, you are talking about a guiding clamp. Not all suppliers and installers make this distinction consistently, which leads to confusion on the construction site.
What is the difference between a single and a double anchor?
This is by far the most common question we encounter. A single anchor fastens one pipe, while a double anchor fastens two pipes running in parallel – typically the supply and return pipes of a heating circuit. At first glance, this seems clear, but in practice, it often happens that an installer orders a single anchor even in a place where a pair of pipes run side by side, which either results in paying for double the number of screws into the substrate or leads to an aesthetically displeasing result (two clamps next to each other look less professional).
Single anchor 601004H, Single anchor 601005H, and Single anchor 601006H are three variants for different pipe diameters – each of them is intended for a different size, which we will explain below. If two identical circuits run parallel in your system, reach for the Double anchor 601007H or Double anchor 601008H – you will save installation time and achieve a cleaner result.
Practical example: in an apartment core, you have a manifold for underfloor heating, from which the pipe runs go exclusively in pairs (supply + return branch). Here, a double anchor is not only more aesthetically pleasing but also technically correct – it keeps both pipes at the prescribed mutual distance, which eliminates contact between them and potential noise from thermal expansion.
How do I understand the numbering of anchors – what do the codes 601004H to 601008H mean?
Manufacturers in the Hepworth line systematically label clamps and anchors. The last number in the code usually reflects the size category or type (single/double). The letter H at the end indicates the belonging to the Hepworth product line. In specific cases:
- 601004H – single anchor for a smaller pipe diameter (typically 15–16 mm outer diameter)
- 601005H – single anchor for a medium diameter (typically 18–20 mm outer diameter)
- 601006H – single anchor for a larger diameter (typically 22–25 mm outer diameter)
- 601007H – double anchor for a smaller paired dimension
- 601008H – double anchor for a larger paired dimension
Always check the outer diameter of the pipe when ordering, not the nominal (DN) dimension. Plastic pipes have a different relationship between the nominal and outer diameter than steel ones – for example, a PP-R pipe DN15 has an outer diameter of 20 mm. This confusion is the source of the most frequent complaints and incorrect orders. For more information on dimensions, see the article What size of pipe clamp do I need – a dimensional overview for 15 mm, 18 mm and other pipes in the Knowledge Center.
Can I use a plastic clamp on a metal pipe?
Technically yes – a plastic clamp can physically encircle a metal (e.g. copper or steel) pipe of the same outer diameter. The question is whether it is suitable and reliable in the long term. Several factors should be considered:
- Temperature – plastic clamps of the Hepworth series are dimensioned for temperature ranges typical for plastic piping systems (usually up to 70–80 °C at operating pressure). Metal pipes in steam lines or high-temperature circuits may exceed these limits.
- Galvanic corrosion – plastic neither conducts electricity by itself nor through the clamp, which can be a problem when combining metal pipes with metal clamps. A plastic clamp is an advantage in this case.
- Mechanical load – heavy copper or steel pipes of larger dimensions (DN25 and above) can overload a plastic clamp, especially when fully filled with water. For these cases, metal clamps with higher load capacity are suitable.
In practice: plastic clamps on copper pipes up to DN20 in floor heating or sanitary lines work without problems. For heavier water lines in steel DN25 and above, I would choose a metal clamp. The topic Plastic vs. metal clamps for pipes – advantages, disadvantages and suitable use is also devoted to a comparison.
What are the requirements for the substrate – where can I anchor a plastic clamp?
A plastic clamp by itself is just a shape – its strength depends on the anchoring element (spike, screw, anchor) you use and on the substrate. Common substrates and recommended solutions:
- Brick / lime-sand masonry – classic anchor with a universal screw, no problem. A suitable anchor is 6×30 mm or 6×35 mm according to the thickness of the clamp.
- Concrete walls and ceilings – hard-fired anchor or expansion anchor, or chemical anchor for higher demands. The pre-drill must be precise, otherwise the anchor floats and the clamp is unstable.
- Gypsum board (without carrier) – unsuitable for standalone clamping of the clamp, unless the line carries only a small diameter. You need to anchor the clamp behind a load-bearing profile or use a special molly anchor.
- Lightweight concrete (Ytong, Siporex) – soft substrate, requires special anchors for lightweight concrete (e.g. type SX or spiral anchors). A classic anchor holds poorly in lightweight concrete.
- Wooden structures – direct screw into wood, the clamp sits firmly. Be careful about the wood moisture in lines with condensation.
From practice: I have seen installations where clamps were embedded in plaster without an anchor – just a screw directly into the mix. After one or two years, two-thirds of the clamps held, one-third moved. Always drill, always use an anchor, always follow the minimum drilling depth of 40 mm (ideally 50–60 mm) in masonry.
Why does the clamp crack or loosen – what am I doing wrong?
Cracking and loosening of plastic clamps belong to the most frequently reported problems. The causes are almost always combined, but can be summarized into several basic groups:
Wrong clamp size
A clamp that is too small creates excessive pressure on the pipe, the plastic body is stressed by bending, and it cracks during temperature changes. A clamp that is too large holds the pipe loosely, the pipe vibrates, makes noise during water flow, and the clamp quickly wears out. A correct clamp should tightly surround the pipe without deformation.
Poor substrate or shallow anchor
An anchor embedded to a depth of 25–30 mm in brick is unstable. During pipe vibrations (pump start-up, water hammer), it easily loosens, the clamp starts to move, and it damages the sealing of the plaster or tiling around it. Always drill at least 50 mm into solid masonry, at least 60 mm in lightweight concrete.
Cracking due to UV radiation
Standard plastic clamps are not intended for outdoor use. Polypropylene without UV stabilizer degrades in the sun – after 2–3 years it becomes brittle and cracks under any mechanical load. If you install it outdoors or in a glazed area with direct sunlight, look for special UV-stabilized versions or use a metal clamp.
Cracking during installation – excessive force
A plastic clamp is closed during installation by a snap or a screw. If you use a screwdriver with too much torque (e.g. an electronic screwdriver without a limiter), you can tear the clamp during installation. Always use a manual screwdriver or a screwdriver with torque setting.
More detailed analyses of specific faults can be found in the article Common problems with plastic clamps – cracking, loosening, inappropriate size.
What spacing should I use for clamps on the pipe?
The spacing of clamps is a standardized value that depends on the pipe material, its outer diameter, and operating temperature. Plastic pipes (PP-R, PEX, PB, PE-RT) have a lower modulus of elasticity than copper or steel – this means they bend more between supports, especially at higher temperatures. Approximate spacing values for common plastic pipes at temperatures up to 60 °C:
| Outer diameter of the pipe | Horizontal run (max. spacing) | Vertical run (max. spacing) |
|---|---|---|
| 16 mm | 500 mm | 700 mm |
| 20 mm | 600 mm | 900 mm |
| 25 mm | 750 mm | 1 100 mm |
| 32 mm | 900 mm | 1 300 mm |
| 40 mm | 1 000 mm | 1 500 mm |
| 50 mm | 1 200 mm | 1 700 mm |
At temperatures above 60 °C (e.g., primary heating circuit with temperatures 70–80 °C), these values decrease – the plastic pipe "softens" and the deflection is more pronounced. In such cases, reduce the spacing by 20–30 %. Near fittings, elbows and branches, always install a clamp within a maximum distance of 150–200 mm from the fitting to eliminate stress on the joint.
More on this topic, including practical examples from layout drawings, can be found in the article Spacing of pipe clamps – how to correctly place the fastening.
Can I use plastic clamps outdoors or in a damp environment?
A damp environment (boiler room, basement, technical room, bathroom) does not affect plastic clamps – on the contrary, plastic is more advantageous than metal here, as it does not corrode. The Hepworth series clamps are made of polypropylene or polyamide material, which is chemically neutral to common technical water, weak acids or alkalis.
The problem is direct UV radiation and extreme temperature ranges outdoors. Polypropylene without UV additives degrades and ages after long-term exposure to sunlight. For outdoor installations – e.g., solar gardens, heat pumps with external piping, façade ducts – it is necessary to use either UV-stabilized plastic clamps or stainless steel clamps.
At the same time: on piping where condensation occurs (cold water in summer), it is important to ensure that the anchor does not press too tightly – otherwise water accumulates at the contact point and causes rusting with metal clamps, while with plastic clamps it is not a problem. However, due to condensation, it is advisable to insert foam pads under the anchor to prevent thermal bridges and unsightly stained plaster.
How many clamps do I need for the entire route – how to calculate it?
The calculation is simple, but in practice, people either buy too little (and have to order again) or too much (and the remainder remains in the warehouse). Procedure:
- Measure the total length of the route in meters (separately horizontal and vertical sections, if relevant)
- According to the spacing table, determine the maximum spacing in mm, convert it to meters
- Calculate: number of clamps = (length of route in m / spacing in m) + 1 (for each starting section)
- Add clamps near each fitting (elbow, reducer, T-piece, branch) – always at least 1 clamp within 200 mm from the fitting
- Add 10–15 % as a reserve for errors, shortening and unexpected route changes
Example: PP-R Ø20 mm route, length 12 m, 4 elbows, 1 T-piece. Horizontal spacing 600 mm = 0.6 m. Number of clamps = 12 / 0.6 + 1 = 21. At fittings: 4 elbows × 2 clamps (on each side) = 8, T-piece = 3. Total: 21 + 8 + 3 = 32 + 15 % reserve ≈ 37 clamps. For such a route, order 40 pieces.
Is it possible to recycle or dispose of plastic clamps in an environmentally friendly way?
Polypropylene and polyamide clamps are technically recyclable, but in practice, they are small shaped plastic parts that are sorted into the yellow bin (plastics) during regular waste sorting. In municipal sorting, they end up according to local capacities – not always being recycled into valuable granulate. If you are replacing clamps in large quantities (e.g., a complete pipeline renovation), hand the plastics over to a collection point or a company that processes plastics.
The lifespan of a plastic clamp in an indoor environment without UV radiation is practically the same as the lifespan of the pipe – 25 to 50 years. Therefore, there is no reason to replace them under normal conditions, unless they are torn by excessive force or unsuitable conditions.
Compatibility – do these anchors work only with the Hepworth system or also with other pipes?
Hepworth series clamps (601004H–601008H) are dimensioned for the outer diameter of Hepworth pipes, which in most cases coincide with the European standard for outer diameters. This means that a clamp for Ø20 mm outer diameter will work with any pipe – PP-R, PEX-a, PEX-b, PB or PE-RT – as long as it has the same outer diameter of 20 mm.
Problems arise when you confuse the nominal diameter (DN or ½″, ¾″) with the outer diameter. For example, a pipe marked ½″ may have an outer diameter of 15 mm, 16 mm or 20 mm depending on the material and standard. Always check the exact outer diameter of the pipe in mm before ordering – you will find it in the technical data sheet of the pipe or simply measure it with a caliper.
More on the compatibility of clamps with specific pipe systems can be found in the topic Clamps for the Hepworth system – compatibility with plastic pipes.
Can I install clamps before or after the pipe installation?
It depends on the design of the anchor. The series of anchors 601004H–601008H have an opening mechanism – a lid or a tongue that opens, the pipe is inserted into the base and the tongue is snapped shut. This means that these anchors can be installed even after the pipe is laid. This is particularly advantageous in renovations, where you cannot pass the pipe through a closed clamp.
On the contrary, some older or cheaper clamps are simple clips without opening – the pipe must pass through the fastening during laying. For most professional installers, openable anchors are clearly more comfortable and faster to install, which means saving dozens of minutes on long routes.
The recommended step-by-step installation procedure is described in the article Installation of plastic clamps on pipes step by step.
Most frequently asked questions (FAQ)
What is the difference between clamp 601007H and 601008H – aren't they both double?
Yes, both are double, but each is intended for a different outer diameter of the pipe. Clamp 601007H is for a smaller size (usually a few pipes Ø16 mm or 2× Ø18 mm), while 601008H is for a larger diameter (e.g., 2× Ø20 mm or 2× Ø22 mm). Before ordering, always measure the outer diameter of the specific pipes with a caliper and compare it with the technical data sheet of the clamp.
Is it necessary to put a rubber pad under the plastic clamp to protect the pipe?
For standard plastic pipes (PP-R, PEX, PB), this is not necessary – plastic clamps have a sufficiently soft and smooth inner surface that does not damage the pipe. Rubber inserts or foam padding are suitable where you want to dampen vibrations or noise (e.g., near a circulation pump or in a cold water line in summer, where condensation can create moisture spots). For sound insulation, special clamps with soft inserts are available.
Can I use one clamp for two pipes of different diameters running next to each other?
No, this is not a technically correct solution. A double clamp is always dimensioned for a specific combination of identical diameters (e.g. 2× Ø16 mm or 2× Ø20 mm). If two pipes of different diameters run next to each other, use a separate single clamp of the correct size for each, or alternatively mount them on a common installation strip.
Can a plastic clamp make noise – what can be done about it?
Yes – if the clamp is too loose, the pipe vibrates within it during water flow or when the pump is switched on, causing squeaking. Solution: check whether you have used the correct size – the pipe should fit tightly in the clamp without play. If the clamp is correct and the noise persists, the cause may be a water hammer in the system or an excessively high flow velocity. Foam or rubber inserts in the clamp will significantly reduce the noise. This issue is discussed in more detail in the article Common problems with plastic clamps – cracking, loosening, unsuitable size.
What is the maximum temperature at which I can use plastic clamps of the Hepworth series?
For most types in this series, the maximum continuous operating temperature is 70 °C, and up to 80 °C in the short term (e.g. system startup). For primary circuits with temperatures above 80 °C or steam pipes, plastic clamps are unsuitable – use metal ones. Always check the technical data sheet of the specific product, as different polymer materials have different temperature limits.
How many clamps should I keep in stock – is it worth buying larger packages?
If it is regular installation work or a larger project, definitely yes. Clamps are also available in larger packages, where the price per piece is lower. For a one-time home repair (changing the route, adding a circuit), it is sufficient to purchase 15% extra according to the calculation from the table. For a service company, it makes sense to always keep common sizes (Ø16, Ø20, Ø25) in stock – these dimensions are repeated on every job.
Conclusion – what to take away from this article for practical use
Plastic clamps and hangers are a small but key component of any pipe installation. A properly chosen clamp – in terms of size, type (single vs. double), spacing and fixing method – determines whether the pipe route will last for decades without problems, or whether it will haunt you with squeaking, cracking and repeated repairs. Invest time in calculating the correct quantity, check the outer diameter of the pipe before ordering, and do not forget to use fixing elements (anchors, screws) dimensioned for your specific substrate.
If you are unsure about the selection, browse the entire category of plastic clamps and compare the available variants. Further practical information can be found in related articles in the Knowledge Centre – especially in the topics How to choose the right plastic clamp for a pipe – single vs. double, Single clamp vs. double clamp – when to use which and Maintenance and inspection of pipe clamps – what to watch out for.
Do you have a question on this topic?
Not sure how to decide or dealing with a specific situation in your home? Write to us – we are happy to help.