Plumbing First Fix Calculator — Pipe & Fittings

First fix plumbing is the installation of all pipework, waste runs, and connections before walls and floors are finished. This includes hot and cold water distribution pipes, waste pipes, soil stack connections, and any manifolds or headers. Second fix is connecting the sanitary ware after plastering. This calculator estimates the hot and cold supply pipe lengths and fittings; it counts waste points for set-out but does not size waste/soil pipe lengths. Use our Pipe Sizing Calculator for supply pipe diameters, and our Waste Pipe Sizing Calculator for waste runs.

Tee (branch) layout uses larger pipes branching to smaller ones at each outlet — uses less pipe but more fittings. Manifold (home run) layout runs individual pipes from a central manifold to each outlet — uses more pipe but fewer joints in walls and allows individual isolation.

A typical 3-bed house has approximately 7 hot water drop points (kitchen sink, bathroom basin, bath, shower, en-suite basin, en-suite shower, cloakroom basin) and 9 cold water points (same plus WCs and outside tap). Waste points typically number 8-9.

Allow 10% extra (factor 1.1) for cuts, waste, and routing adjustments. For complex buildings with lots of bends and obstacles, increase to 15% (1.15). This ensures you order enough material without excessive waste.

UK push-fit manifolds (e.g. JG Speedfit, Reliance) are modular — typically supplied as 2, 3 or 4-port units that join together to build a larger bank, so you are not limited to fixed sizes. Size for the maximum number of outlets on a circuit: a typical 3-bed house works out at about 9 cold ports and 7 hot ports, so a combined or banked manifold of around 9 ports per side covers it. Keep manifolds in an accessible location (airing cupboard or utility room) for isolation and maintenance.