UK Plumbing Regulations — What You Can (and Can't) DIY
Confused about what plumbing work you can legally do yourself in the UK? Here's the complete regulatory landscape — Water Regs, Building Regs, Gas Safe.
Step-by-step method
1. Water Supply (Water Fittings) Regulations 1999
All materials in contact with mains water must be WRAS-approved. You can DIY, but non-approved parts are illegal to install.
2. Building Regs Part G — hot water
Any new/altered unvented cylinder needs G3-registered installer. Any new/altered thermostatic mixing valve in a new bathroom needs certificate.
3. Building Regs Part P — electrics
New circuits, bathroom electrics or consumer unit work must be by a Part P registered electrician OR building control notification.
4. Gas Safe
Anything involving gas — from moving a pipe to installing a hob — must be by a Gas Safe registered engineer. Non-compliance is a criminal offence.
5. What you CAN DIY
Any cold water work in copper/plastic downstream of stopcock, radiator swap, tap swap, toilet swap, shower plumbing (not electric shower wiring), waste pipework.
Frequently asked questions
Can I fit my own unvented cylinder?+
No — Building Regs Part G requires a G3-registered engineer. Doing it yourself invalidates house insurance.
Do I need permission for a new bathroom?+
Notify Building Control if adding a new WC or shower (Part G water efficiency + Part H drainage) or if any new electrical circuits are added (Part P).