This is an honest comparison, not a hit piece on copper. Both are valid gas pipework. Flexigas wins on three things that matter on most jobs: time, joints and labour. You pull a continuous flexible run through the joists like electrical cable, so an install goes in up to 80% faster than copper (around five times the speed), with no soldering, no blowtorch and no hot works permit. Long runs mean fewer fittings, so fewer concealed joints and fewer leak points. No elbows means a lower total installed cost, especially in the larger DN28 to DN54 sizes, on both materials and labour. Copper still earns its place on short simple runs and exposed runs where a rigid look is wanted, and because the internal diameters match you can switch between the two mid-run. One catch: pressure loss in Flexigas differs slightly from copper, so you cannot swap like-for-like at the same diameter. Size it with the in-browser calculator.
If you already fit copper for gas, the honest question is not which is better in the abstract. It is which one gets a compliant install in first, at lower cost, with fewer things to go wrong later. Both Flexigas CSST and copper are valid gas pipework fitted by a Gas Safe registered engineer. They win in different places.
The short version
| What you care about | Flexigas CSST | Copper |
|---|---|---|
| Install speed | Up to 80% faster (around 5x) | Baseline |
| Joints per run | Few. Long continuous runs. | Many. A fitting at every change of direction. |
| Concealed joints behind walls | Fewer, so fewer leak points | More, by the nature of the system |
| Hot works | None. Mechanical seal. | Soldering. Blowtorch. Hot works permit. |
| Routing around obstacles | Flexes around them | Soldered fittings around them |
| Total installed cost | Lower, especially DN28 to DN54 | Higher on most runs |
| Short, simple, exposed runs | Works, but copper is fine here too | Often the easier pick, and the rigid look |
1. Speed: pull it through like cable
This is the headline difference, and it is real. Flexigas installs up to 80% faster than copper tube, around five times the speed on a typical run. Copper is built up fitting by fitting: cut, ream, clean, flux, assemble, solder, repeat at every bend. Flexigas is a continuous flexible tube you pull through the joists like electrical cable, then terminate only where you need a connection.
It comes in long coils, so on most domestic runs you can pull a single length from meter to appliance with no joints in between, assuming the route allows. There is no soldering along that run, so the time you would spend making up copper joints just disappears. As the brochure puts it, the only thing you will be burning is through the job.
2. Joints: fewer fittings, fewer concealed leak points
Every joint is a potential leak point, and the ones you cannot inspect again matter most. Copper needs a fitting at every change of direction, and on a real route many end up concealed behind walls, under floors and above ceilings. Because Flexigas runs as long continuous lengths, you make far fewer joints, so fewer concealed joints and fewer leak points buried in the structure. This is not a claim that copper joints fail: properly made they are sound. It is the simpler point that the fewer joints a system needs, the fewer things there are to make, test and worry about later.
3. Hot works: no blowtorch, no permit
The Flexigas seal is mechanical. The corrugated stainless steel tube self-flares against a brass seat as you tighten the fitting with two spanners. No solder, no flux, no jointing compound, no PTFE on the seal, so no blowtorch and no hot works. That means no hot works permit on occupied buildings and commercial sites, and it is safer near joists and insulation with no open flame next to timber, membranes or loft insulation. Copper means soldering: a known, controlled process engineers do every day, but it is hot works, and hot works carry a permit, a fire watch and a risk wherever you do them.
4. Cost: no elbows, lower installed total
No elbows means a lower total installed cost than copper, on both materials and labour. Every copper elbow and coupling is a part you buy plus the solder and flux to fit it, and a continuous Flexigas run needs far fewer fittings. The bigger lever is labour: an install that goes in around five times faster is far fewer hours on site, usually the largest line on a gas job.
Flexigas is especially economical in the larger DN28 to DN54 sizes, where copper fittings and the labour to make them up get expensive and the saving from eliminating them is widest. On short DN15 and DN22 runs with one or two joints the gap is narrower, which is part of why copper still makes sense in some places.
5. Routing: flex around what copper solders around
Real routes are full of obstacles: steels, ducts, other services, awkward corners. Copper deals with them by soldering a fitting to change direction around each one. Flexigas deals with them by bending, so a sweeping change of direction costs you a bend, not a fitting. A sizing point worth knowing: a sweeping bend made by the tube adds only the equivalent length of a 90 degree bend rather than a full elbow fitting, so on long or congested runs that adds up in your favour.
6. Where copper still makes sense
An honest comparison says this plainly: copper is not beaten everywhere.
- Short, simple runs. A straight run with one or two joints is quick in copper, where the Flexigas advantages are smallest.
- Exposed runs where a rigid look is wanted. In a plant room or boiler house, or anywhere the pipework is on show and the customer or specifier wants the clean rigid line of copper, copper is the better aesthetic. Flexigas is built to be pulled through and concealed.
You do not have to choose one for the whole job. The internal diameters match copper, so you can switch between the two mid-run through approved BSP thread connectors: pull Flexigas through the difficult concealed section, then transition to copper for the exposed final tail, or complete the whole install in Flexigas. Around 99% of the way you install copper applies to Flexigas, so this is not a system you learn from scratch.
7. The one thing you cannot do: swap diameters like-for-like
This is the catch that trips people up. Pressure loss in Flexigas is slightly different to copper. The corrugated bore does not flow identically to smooth copper tube at the same nominal size, so you cannot swap a copper diameter for the same Flexigas diameter and assume the install works.
Size the run properly. On some runs the calculation will tell you to go up a size versus the copper you would have used. That is normal and honest, and even allowing for it the time, joint and labour savings still come out ahead. Use the Flexigas in-browser sizing calculator at flexigas.com/gas-pipe-sizing-calculator/: it runs in your browser, free, no app to download, and accounts for the equivalent lengths of bends and fittings so you size right first time. For anything more than a short straight run with one or two fittings, use it.
The verdict
Both are valid gas pipework, fitted by a Gas Safe registered engineer to the same standards. Copper holds its ground on short simple runs and exposed runs where a rigid look is wanted. But on most real jobs Flexigas wins where it counts: time, joints and labour. Reach for the right one per job, size it with the calculator, and on a lot of jobs that will be Flexigas.