Copper versus polypropylene: where copper earns it
Point by point
| Criterion | Copper | PP-R |
|---|---|---|
| Pipe and fitting cost | highest | lowest |
| Tooling | torch and solder, or press jaws | welding iron |
| Hot work | yes when soldering — a real risk indoors | no, the iron has no open flame |
| Working temperature | the joint sets the limit: soft solder and press up to ~110 °C, brazing into the hundreds | 70 °C continuous, up to 90 °C for short periods |
| Lifespan | 50 years and more, regardless of the joint | 50 years by the standard at 70 °C; less at 90 °C, and it depends on weld quality |
| Looks when exposed | good | utilitarian |
| Bore at the same outer diameter | wider — thin wall | narrower — thick wall |
| UV exposure | no problem | needs a duct or insulation |
| Catch | galvanic pair with steel, needs a brass transition | an overheated joint narrows the bore invisibly |
Copper earns its price when
- Boiler rooms and heat-source pipework: temperatures and fault conditions where plastic runs at its limit.
- Exposed runs on show: copper reads as part of the room rather than a temporary fix.
- A house built to outlast you, where redoing the work costs more than the material ever did.
PP-R is enough when
- Concealed hot and cold water in a flat — ordinary temperatures, and the joint gets buried and forgotten.
- The budget is tight and the metreage is long: the price difference goes into other work.
- You're doing it yourself and aren't about to learn soldering or buy a press tool.
The rule where materials meet
Never join copper directly to steel: with water present they form a galvanic pair and the steel starts to corrode. Make the transition through a brass or bronze fitting.
In flow order, copper goes after steel: copper particles carried by the water accelerate corrosion of steel pipe downstream.
About soldering indoors
Soldering copper means open flame in a chase, next to timber, insulation and wiring. In a flat or a timber-framed house that's hot work in the full sense — which is why press fittings keep winning indoors: same result, no flame.
- If you do solder: clear combustibles within a metre, back the area with a non-combustible mat and keep an extinguisher to hand.
- The real danger is smouldering inside a floor void or insulation — it shows up hours later. Check the area again a couple of hours after finishing.
- In a finished room, with wallpaper and laminate around the joint, press costs less than the consequences.
Common questions
What are you paying extra for with copper?
Temperature (up to 110 °C at a soldered or press joint, against 70–90 °C for PP-R), a service life measured in decades, and looks that need no boxing in. In a plant room and on exposed runs that is worth it; concealed hot and cold water in a flat is covered for less by PP-R.
Can copper be joined straight to steel pipe?
Not directly: with water present the two form a galvanic pair and the steel starts to corrode. Put a brass or bronze adapter between them, and in the direction of flow place copper after steel, never before it.
Is soldering copper indoors dangerous?
Torch soldering means an open flame in a chase next to timber, insulation and wiring — hot work in the proper sense. In a finished flat people use press fittings instead: same result, no flame. If you do solder, use a non-combustible screen, keep an extinguisher to hand and check the area again a couple of hours later.