Redoing the plumbing in a renovation means choosing a material for thirty years. Copper used to reign, PEX democratised the job, multilayer reconciled the two. Here is how to decide for your project.
PEX: the economical one
Semi-rigid polyethylene pipe, blue (cold) or red (hot). Pros: unbeatable price, fast flame-free installation, ideal in a home-run (‘octopus') layout from manifolds — one continuous pipe per outlet, zero hidden fittings. Cons: expands a lot, not for exposed runs (unsightly), UV-sensitive. The standard choice where everything runs concealed.
Multilayer: the versatile one
PEX with an aluminium core: it keeps the shape you give it, barely expands, works concealed or neatly exposed. Press or compression fittings. A little dearer than PEX, far more forgiving. The best value in a full renovation, including for feeding hydronic underfloor heating.
Copper: the durable one
Fifty years and more, recyclable, handsome when exposed (industrial-style renovations leave it visible on purpose). But: torch-brazed joints (a skill), high metal price, sensitive to aggressive water. It is often kept for visible runs, with synthetic pipe inside the walls.
Waste pipes: PVC without hesitation
Diameters to respect: 32 mm basin, 40 mm shower and sink, 100 mm WC. The rule that avoids 90 % of problems: 1 to 3 cm of fall per metre — never less (stagnation), never much more (water leaves without the solids).
The supply diameters (PEX/multilayer)
- Ø 12 mm: basin, WC, small hand basin.
- Ø 16 mm: kitchen sink, shower, washing machine, dishwasher.
- Ø 20 mm: bathtub, manifold feed, high-flow rain shower.
The critical point in renovation: the bathroom
The room where plumbing and coverings meet. Waterproofing under tiles (liquid membrane) in shower zones, accessible floor drain, and if you dream of a warm floor: yes, wood flooring in a bathroom is possible with the right species and finish — our dedicated guide explains which.
Pipes run, pressure-tested, walls closed: next logically comes levelling the floors and then the coverings — see the full order of works.