SH Plumbing & Property Maintenance

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Pipes, Fittings & Valves Explained (Level 1)

This lesson is all about the main parts you’ll see in most homes: the pipes themselves, the fittings that join them, and the valves that turn water on and off.

You don’t need to remember every name perfectly. The goal is simply that, when you look under a sink or in an airing cupboard, things start to make more sense.

Common Pipe Sizes

Most homes use just a few main pipe sizes. Once you know these, you’ll recognise a lot of what you see:

  • 15mm pipe
    • The most common size in a typical house
    • Often used for feeds to taps, toilets, and radiators
  • 22mm pipe
    • Slightly bigger than 15mm
    • Used for main hot and cold runs and some boiler or cylinder connections
  • 28mm pipe (and bigger)
    • Used for main supplies or larger systems
    • Less common in small DIY jobs, but good to know it exists

If you can remember 15mm and 22mm, you’ll be able to understand a lot of the pipework in a typical house.

Copper Pipes

What copper pipe looks like:

  • Hard metal tube
  • Shiny copper colour when new, turning dull brown over time

Where copper is used:

  • Hot and cold water pipes
  • Central heating systems and boiler connections

Why plumbers like copper:

  • Very strong and long-lasting
  • Handles heat and pressure well
  • Great for hot water and heating

Things to know as a beginner:

  • Copper often needs soldered joints (using a blowtorch and solder) or compression fittings (nuts you tighten with spanners).
  • It takes more practice and the right tools, so many beginners find plastic pipe easier to start with.

Plastic Pipes (Push-Fit Style)

What plastic pipe looks like:

  • White, grey, or black flexible pipe
  • Often slightly bendy compared to copper

Where plastic is used:

  • Hot and cold water pipes
  • Some central heating systems (always check the manufacturer’s rules)

Why beginners like plastic:

  • Quicker and easier to install than copper
  • Can bend around corners and fit into tight spaces
  • Good for simple DIY runs if you follow the instructions

Important safety points for plastic:

  • Always use the correct pipe inserts inside the pipe ends.
  • Push the pipe fully into the fitting until it hits the built-in stop.
  • Follow the manufacturer’s instructions carefully for each brand of fitting.

Waste Pipes

Waste pipes carry dirty water away from your home. They are usually larger than the pipes that bring clean water in.

Common waste sizes in a home:

  • 32mm waste pipe (about 1¼”)
    • Used for basins and small sinks
  • 40mm waste pipe (about 1½”)
    • Used for kitchen sinks, baths, and showers
  • 50mm and bigger
    • Used when more water needs to drain, or several appliances join together

Waste pipes are almost always plastic and are joined with either:

  • Push-fit fittings (they push together with rubber seals), or
  • Solvent weld fittings (glued together using special solvent cement)

Basic Fittings You’ll See Everywhere

Fittings are the pieces that help pipes change direction, change size, or join together.

  • Elbows (bends)
    • Change the direction of a pipe (for example, a 90° corner)
    • Used whenever a pipe needs to go around an obstacle
  • Tees
    • Shaped like a “>”T”
    • Used to split one pipe into two, or join three pipes together
    • Common when adding a new tap, radiator, or appliance feed
  • Straight couplers
    • Join two pieces of pipe in a straight line
    • Useful for repairs, like cutting out a damaged section of pipe
  • Reducers
    • Connect a bigger pipe to a smaller pipe (for example, 22mm down to 15mm)
    • Used when you branch off a main pipe to feed a single smaller item

Each of these fittings has versions for both copper and plastic pipe, so you’ll see the same shapes in different materials.

Valves – Controlling the Water

Valves are like switches for your water. They let you turn the water on and off where you need to.

  • Isolation valves
    • Small valves fitted on the pipe that feeds one item (like a tap, toilet, or appliance)
    • Let you turn off the water just to that item instead of the whole house
    • Often turned with a small screwdriver or a little lever
  • Stopcock / stop tap
    • The main valve for the whole house
    • Turn clockwise to turn water off
    • Turn anticlockwise to turn water on

If you can recognise these pipes, fittings, and valves, you’re already thinking like a Level 1 plumber. In the next lesson, we’ll look at the tools and materials that help you work with them safely.

Next lesson: Plumbing Tools & Materials for Beginners.