Land Drain Calculator

How the land drain calculator works

Estimates perforated pipe length and gravel for land drainage. The calculator takes your dimensions and supplier rates, applies a standard UK trade formula, and returns a quantity with an indicative cost. Every figure is an estimate — site conditions always move the final number.

Typical UK drainage and earthworks wastage

Excavated soil bulks up 15–35% when lifted, so skip capacity fills faster than the in-situ volume suggests. Plan for a 1.25× factor when hiring away muck. Our defaults reflect common UK trade allowances, and can be adjusted upwards for non-standard geometry or downwards where experience supports a lower figure.

What this tool does not do

It does not replace a professional quote, factor regional pricing, assess structural adequacy, or confirm Building Regulations compliance. Those remain the responsibility of a suitably qualified designer, surveyor, or your building control officer.

On-site considerations for land drain

Excavations over 1.2 m deep need shoring or battered sides — the HSE guidance on trench collapse is not optional. Check for buried services with a CAT scanner before digging.

Building Regulations and compliance

Foul and surface water drainage to a public sewer is governed by Approved Document H and Sewers for Adoption. Soakaways need a permeability test (BRE 365) to size correctly. When in doubt, a pre-application enquiry to the local authority can give early clarity, which tends to be less costly than retrospective correction.

Before you order

Buy plastic drainage pipe in standard 3 m or 6 m lengths with integral seal joints. Cutting short lengths on site wastes material and fittings. Cross-checking the calculator’s output against a supplier quote helps catch differences in pricing assumptions — ask for exact product specifications (grade, finish, batch number) and confirm delivery timescales against your programme.

Adjusting the defaults

Every input in this calculator is editable. Enter your own dimensions, supplier prices, and wastage allowance — the output recalculates instantly. If the defaults feel off for your region or project type, your own numbers always override them.

Using this land drain calculator alongside other BuildMetricLab tools

This calculator works best as part of a planning workflow. Pair the quantity with our project contingency, labour-hours, and material-cost calculators to build a complete estimate before you pick up the phone to a supplier. All BuildMetricLab tools run entirely in your browser — no sign-up, no data sent anywhere, and every formula is shown on-page so you can audit the maths.