What is plumbing first fix?

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.

What is the difference between manifold and tee layouts?

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.

How many drop points does a typical 3-bed house have?

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.

What pipe waste factor should I allow?

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.

What size manifold do I need?

Manifolds are available in 4, 6, 8, 10, and 12 port sizes. Size the manifold for the maximum number of hot or cold outlets. A typical 3-bed house needs an 8-port manifold for cold and a 6-port for hot. Manifolds should be in an accessible location (airing cupboard or utility room).

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Plumbing First Fix Calculator — Pipe & Fittings

Calculate pipe run lengths, fittings count, and drop points for first fix plumbing. Compare manifold vs tee distribution layouts.

Distribution Layout

Tee (branch) or manifold (home run)

Property Type

Property size for drop point estimate

Average Run Length

Average distance from manifold/header to outlet

How We Calculate This

This calculator estimates the pipe lengths, fittings, and drop points for first fix plumbing based on property size and distribution layout choice.

Estimation method

Drop points: Estimated from property type and rooms
Tee pipe: Main run + branch runs to each outlet
Manifold pipe: Individual run to each outlet from manifold
Fittings: ~4 per drop (tee) or ~2 per drop (manifold)
Waste factor: 10% extra for cuts and adjustments

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.