Flux
In plumbing
A paste brushed onto cleaned copper before a soldered joint is made. It keeps the surface free of oxide while it is heated, so that the solder can flow into the joint. Leftover flux goes on attacking the copper, so excess is wiped off and the pipework is flushed through before it is used.
Using Flux in a plumbing system
Updated
A distinction worth remembering
A leak-free connection can still be strained by unsupported pipework, movement or expansion. Revision should connect joint type, material, access and support to the service conditions. Installation details belong to the relevant system manufacturer's instructions and supervised training.
Questions to take further
- Does a joint that looks dry immediately prove the work is finished?
- No. Appropriate testing, inspection and checking the system under its intended conditions are part of the work. Access for maintenance and suitable support matter too.
Sources
- Skills England: plumbing and domestic heating technician — The systems, materials, planning and customer responsibilities in the England occupational standard.
Where Flux fits in the learning path
The Pipework & Jointing section covers these topics:
- Pipe Materials
- Pipe Joints and Fixings
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- Pipe Joints and FixingsPipework & Jointing
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A copper fitting with a ring of solder already inside each end. The pipe is cleaned, fluxed and pushed in, then the fitting is heated until a bright line of solder shows all round each mouth. Solder used on drinking-water pipework is lead-free, and because the job needs a flame, fire precautions come first.
Solder ring fitting
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Solder ring fitting — Integral solder ring
A copper fitting with a ring of solder already inside each end. The pipe is cleaned, fluxed and pushed in, then the fitting is heated until a bright line of solder shows all round each mouth. Solder used on drinking-water pipework is lead-free, and because the job needs a flame, fire precautions come first.
Read the Solder ring fitting 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.