Branch pipe
In plumbing · also called Branch discharge pipe
The length of waste or soil pipe that carries the discharge from one appliance, or a few, to the stack or straight to a drain. Its size, length and fall are matched to the appliance so that it neither blocks nor siphons the trap at its upper end.
Using Branch pipe in a plumbing system
Updated
A distinction worth remembering
Check the fall of each pipe, where each branch meets the stack, and how air reaches the pipe behind the water. Most gurgling, slow or smelly wastes trace back to one of those three.
Questions to take further
- Can an air admittance valve replace a vent pipe?
- It can stand in for an open vent on some stacks and branches inside a building, where the guidance for that nation allows it. A valve only lets air in, so the drainage system still needs an open vent somewhere to let air out.
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.
Where Branch pipe fits in the learning path
The Above-Ground Sanitation and Drainage section covers these topics:
- Sanitary Appliances and Traps
- Waste and Soil Pipework
- Blockages, Drains and Sewers
Read, practise, return
1. Read it in context
- Waste and Soil PipeworkAbove-Ground Sanitation and Drainage
2. Try recalling, then explore practice
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3. Return to the meaning
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Recall a related term
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The downward slope given to a waste pipe or drain so that water runs away by gravity. It is quoted as a drop for each metre of run or as a ratio such as 1 in 40. Too little fall lets solids settle; too much on a small waste can empty its trap.
Compare related terms
Open a meaning to compare its role with Branch pipe, or follow its full entry.
Fall — Gradient
The downward slope given to a waste pipe or drain so that water runs away by gravity. It is quoted as a drop for each metre of run or as a ratio such as 1 in 40. Too little fall lets solids settle; too much on a small waste can empty its trap.
Read the Fall entrySoil stack — Soil and vent pipe
The main vertical pipe that carries waste from toilets and other appliances down to the underground drain. Its top usually continues up into open air, or ends in an air admittance valve, so that air can get in and the water in the traps is not sucked out as waste rushes down.
Read the Soil stack 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.