Industry Applications

May 23, 2026

P-Clips for HVAC and Pipework: Copper Pipe, Refrigerant Lines and Ductwork

P-clip specification for HVAC and building services pipework — copper pipe sizing, refrigerant lines, compressed air, and material selection for indoor and outdoor runs.

P-clips are the standard fixing method for copper pipework, refrigerant lines, and compressed air distribution in HVAC and building services installations. The key decisions are straightforward: match the clip diameter to the pipe OD, choose the right material for the environment, and space the clips to the appropriate support interval. This guide covers all three for the common pipe sizes and system types encountered in HVAC work.

Sizing for Copper Pipe

Standard copper tube in the UK follows a nominal size that matches the outer diameter directly — so 15 mm copper has a 15 mm OD, 22 mm copper has a 22 mm OD, and 28 mm copper has a 28 mm OD. This makes clip selection straightforward: the clip nominal diameter equals the pipe nominal size.

Copper Pipe Size	Pipe OD	Clip Size	Fixing Hole
8 mm	8 mm	8 mm	M4/M5
10 mm	10 mm	10 mm	M6
15 mm	15 mm	15 mm	M6
22 mm	22 mm	22 mm	M6
28 mm	28 mm	28 mm	M6
35 mm	35 mm	35 mm	M8
42 mm	42 mm	42 mm	M8
54 mm	54 mm	54 mm	M10

Important Always use rubber-lined P-clips on copper pipe. An unlined steel clip in direct contact with copper creates a galvanic couple that accelerates corrosion of both metals. The EPDM liner prevents metal-to-metal contact and protects the pipe surface.

Insulated and Lagged Pipe

For pipework with foam insulation, Armaflex, or other lagging applied, measure the outer diameter of the complete insulated assembly and select the clip accordingly. A 22 mm copper pipe with 13 mm wall insulation has an insulated OD of approximately 48 mm — requiring a 50 mm nominal clip, not a 22 mm clip.

The EPDM liner will contact the insulation surface directly. This is acceptable and common in building services installations, provided the insulation is firm enough to support the clamping load without deforming. For very soft insulation, use a wider-band heavy-duty clip to spread the contact area.

Refrigerant and AC Lines

Refrigerant lines in split AC and commercial refrigeration systems are typically copper or aluminium, running in pairs (liquid and suction). Key considerations:

Suction lines are often insulated — size for the insulated OD as described above
The two lines can be clipped together or separately — if clipped together, measure the combined OD of the bundled pair
For outdoor condenser unit connections, specify stainless steel clips if the run is fully exposed to weather
The EPDM liner is compatible with the condensation and temperature cycling typical of refrigerant line service

Compressed Air Pipework

Compressed air distribution in workshops and industrial facilities is commonly run in steel, copper, or aluminium tube. P-clips are the standard support method. For compressed air:

Size clips to the pipe OD as per the copper pipe table above, adjusted for the pipe material's actual OD
Standard P-clips are adequate for most compressed air pipework — the operating pressures do not require heavy-duty specification unless the pipe diameter is large
Space clips at the intervals in the table below, consistent with the pipe material and diameter
Near compressors and in plant rooms, the clips will be subject to elevated vibration — reduce spacing by 30% in these zones

Material Selection for HVAC

The majority of HVAC and building services pipework is installed indoors in low-humidity commercial or industrial environments. Zinc-coated mild steel is the standard and correct specification for these applications.

Specify stainless steel for:

External runs exposed to weather
Plant rooms or roof installations subject to regular moisture or condensation
Food production facilities where any water ingress requires stainless throughout
Coastal buildings where salt-laden air affects external and semi-exposed locations

Spacing Guidelines

Pipe Size	Horizontal Spacing	Vertical Spacing
15 mm copper	1,200 mm	1,800 mm
22 mm copper	1,800 mm	2,400 mm
28 mm copper	1,800 mm	2,400 mm
35–42 mm copper	2,400 mm	3,000 mm
54 mm copper	2,700 mm	3,000 mm
All sizes, near bends/fittings	Within 150 mm of any fitting	—

These figures are broadly consistent with BS EN 806 guidance for copper tube. Always check the applicable building services specification for the project.

FAQs

What size P-clip do I need for 22 mm copper pipe?

For 22 mm copper pipe, use a 22 mm nominal diameter P-clip. The nominal clip diameter matches the outer diameter of the copper pipe directly. If the pipe has insulation or lagging, measure the insulated assembly OD and size accordingly.

Do P-clips damage copper pipe?

Not when correctly specified. The EPDM rubber liner prevents metal-to-metal contact between the clip band and the copper surface. Without a liner, the steel band would cause galvanic corrosion and abrasion damage to the copper. Always use rubber-lined P-clips on copper pipe.

What P-clip size is needed for 15 mm copper pipe?

15 mm copper pipe has an outer diameter of 15 mm. Use a 15 mm nominal P-clip. This is one of the most common sizes in HVAC and plumbing installations.

Can P-clips be used on insulated copper pipe?

Yes. Measure the outer diameter of the insulated assembly and select the clip to match that measurement. The EPDM liner contacts the insulation surface rather than the pipe directly.

How far apart should P-clips be on copper pipe?

For horizontal copper pipe runs, BS EN 806 guidance suggests approximately 1,200 mm for 15 mm pipe, 1,800 mm for 22 mm, and 2,400 mm for 28 mm. Always place a clip within 150 mm of any bend or fitting.

P-Clips for HVAC and Pipework

British-made rubber-lined clips from 5 mm to 90 mm nominal diameter. Filter by size and material.

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