Combined sewer
In plumbing
A sewer that carries foul water and rainwater together to the treatment works. Many older areas have them. In England's guidance, a rainwater pipe discharging into a combined system does so through a trap so that sewer air stays out.
Using Combined sewer in a plumbing system
Updated
A distinction worth remembering
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.
Where Combined sewer fits in the learning path
The Rainwater, Maintenance and Environmental Protection section covers these topics:
- Rainwater Gutters and Downpipes
- Water Efficiency and Reuse
- Maintenance and Environmental Protection
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- Rainwater Gutters and DownpipesRainwater, Maintenance and Environmental Protection
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In a separate system, the sewer that carries rainwater from roofs, roads and paving, usually straight to a river or stream without treatment. Foul water must never be connected to it, and nothing but rain should go into its gullies.
Surface water sewer
Read the Surface water sewer entryCompare related terms
Open a meaning to compare its role with Combined sewer, or follow its full entry.
Surface water sewer
In a separate system, the sewer that carries rainwater from roofs, roads and paving, usually straight to a river or stream without treatment. Foul water must never be connected to it, and nothing but rain should go into its gullies.
Read the Surface water sewer entryPublic sewer
A sewer owned and looked after by a water and sewerage company. A pipe becomes a sewer once it carries flow from more than one property. A blockage in a public sewer is the company's to clear, so a problem shared with neighbours is reported to it rather than tackled alone.
Read the Public sewer entryBefore 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.
A definition is a start. Using it in a real question is where it sticks.