Rainwater Gutters and Downpipes
Rainwater, Maintenance and Environmental Protection · Plumbing
Rain on a roof has to be caught, carried down and sent somewhere sensible. This topic follows it from the gutter to the ground and covers the checks that keep it flowing.
A gutter catches water at the eaves, an outlet drops it into a downpipe, and at ground level a shoe over a gully or a direct drain connection carries it off. PVC-U, cast iron and aluminium all behave differently, and plastic needs room at its joints to expand.
In England, Approved Document H guidance asks for any gutter fall to run towards the nearest outlet and for a downpipe at least the size of the outlet feeding it. Each millimetre of rain on a square metre of roof is a litre of water to move.
Requirement H3 in England puts soaking into the ground first, then a watercourse, then a sewer last. Many faults can be read from the ground, and work at height starts with asking whether a ladder is needed at all.
Follow the water from roof to ground
Updated
How to reason about the system
Check that the gutter falls towards its outlet, that the downpipe is big enough for the outlet feeding it, and where the water goes at the bottom. Overflow, drips and stains on the wall show which of those has failed.
Questions to take further
- Should my downpipe go into the sewer?
- In England the order of preference is to let rainwater soak into the ground, then send it to a watercourse, and only then to a sewer. In an area with separate sewers, rainwater never goes into the foul one.
Sources
- GOV.UK: Approved Document H — Guidance for England on above-ground drainage, traps, venting, access and rainwater disposal; guidance is not itself the legislation.
- HSE: ladders and stepladders — When a ladder is a reasonable choice for work at height in Great Britain, and how to use one safely.
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Learning content, not a qualification: it won't make you competent, certified or registered. Follow the regulations that apply and a qualified plumber before acting. About our content
Lessons on the plumbing path
- Gutters, downpipes and outlets
- Falls, sizing and overflow
- Where rainwater goes
- Gutter checks and working at height
Terms to know
Before you start: some plumbing work is regulated or notifiable
Some water fittings work needs notice to, and consent from, the water supplier before it starts. Check the rules where you live.
Gas work is for competent workers covered by a Gas Safe registered business in Great Britain. Northern Ireland has separate gas regulations. Do not work on gas pipes or appliances yourself.
In England, installing an unvented hot-water system over 15 litres is notifiable building work: use a competent installer registered with a competent-person scheme, or tell building control before work starts. Leave this work to a suitably skilled person.
Wales, Scotland and Northern Ireland have their own water and building rules; check which apply before work starts. Electrical connections belong with an electrician.
This guide does not qualify you or make you competent, approved or registered for plumbing, gas or unvented work.