Plumbing reference: threads, pipe sizes and materials, in brief
Short, practical answers to the questions every build runs into: what size is a 1/2″ thread, which pipe matches which, what that fitting is actually called. The same data our builder is built on.
The basics
Sizes, materials and the words you need before you can buy anything or build it.
Thread sizes
BSP pipe thread table: outer diameter in mm for 1/4″–2″, threads per inch, how to measure a thread with a caliper and tell male from female.
Pipe diameters
What separates a “25 pipe” from a “3/4 pipe”: PP-R, PEX, multilayer, copper, HDPE and steel size ranges — outer diameter, inner bore and nominal size.
Pipe materials
Choosing pipe material for water, heating and house supply: PP-R, PEX, multilayer, copper, HDPE, steel — how each is joined and where each doesn't belong.
Glossary
Plumbing terms explained: union, nipple, reducing bush, eccentric, manifold, bypass, check valve, pressure testing and more — 32 words, one job each.
What to choose
Comparisons with no “best overall”: where each option wins and where it loses.
PP-R or multilayer
Polypropylene versus multilayer pipe compared: cost, tools, repairability, where each one belongs and the weak spot of both systems.
PEX or multilayer
PEX versus multilayer pipe compared: flexibility, shape memory, fittings, price, and which one is safer buried in screed or run from a manifold.
PTFE or flax
PTFE tape, flax with paste, anaerobic gel and sealing cord compared: what holds where, what tolerates backing off, and what won't split brass.
Press or compression
Press fittings versus compression: tool cost, reliability, servicing, and why a compression joint must never be sealed inside a wall.
Copper or PP-R
Copper versus PP-R pipe: lifespan, temperature, price, tooling, and where copper genuinely earns its cost instead of being an overspend.
What to draw plumbing in
What people draw water and heating layouts in: paper, CAD, BIM packages and free online builders — what each one gives you, what it does not, and when each fits.
Instead of CAD
What people reach for when the drawing programs turn out to be heavier than the drawing.
Instead of AutoCAD
Free alternatives to AutoCAD for water and heating layouts: free CAD, 3D modellers and a builder over a parts catalogue — what each one replaces, what it does not, and how to tell whether the job needs CAD at all.
Instead of a 3D modeller
What to use instead of SketchUp when the model is made of pipes: what a general 3D modeller gives you, the five questions it cannot answer, and when a parts-based builder gets you to a shopping list faster.
In practice
What to do when it leaks, hammers, freezes or the pressure swings.
Water pressure
Normal water pressure in a flat or house, how to measure it with a gauge, what pipes tolerate, and when a pressure reducing valve is worth fitting.
A joint is leaking
A leaking thread or fitting: how to stop it, what can be tightened and what must be rewrapped, and which temporary fixes hold until a proper repair.
Shut-off valves
Ball valve, globe valve, full bore versus standard bore: how they differ, where each belongs and how many isolation points a flat actually needs.
Frozen pipes
Why a frozen pipe bursts, what depth to lay a supply line, how insulation and heating cable actually work, and how to thaw a pipe safely.
Banging pipes
Why pipes bang when a tap closes or the washing machine fills, what it damages over time, and what actually helps: arrestors, reducers, clips and sizing.
Assemblies
Ready piping layouts: which parts you need, in what order, and why exactly that order.
Water heater piping
Piping diagram for a storage water heater: safety group, check valve, DHW expansion vessel. Why the relief valve drips and what the vessel fixes.
Water inlet in a flat
What a flat's water inlet is made of and why in that order: valve, strainer, meter, check valve, reducer — on a live schematic you can open and rebuild.
Inlet from a borehole
The borehole water inlet: pump, well head, pressure vessel, pressure switch, filters and manifold — the order it is built in and the reason for each part.