A practical way to decide which plumbing jobs are safe and sensible to DIY in a UK home and which need a qualified plumber or Gas Safe engineer, with the legal limits, the risks and how to choose a professional.
Plenty of plumbing jobs are well within reach of a careful beginner, and doing them yourself can save a call-out charge. Others carry legal requirements or real risks of flooding, scalding or gas leaks. This guide sorts jobs into three groups and gives a simple test for anything in between.
Usually fine to DIY
- bleeding radiators and topping up a combi boiler's pressure (following the manual);
- replacing a tap washer or cartridge;
- clearing a blocked sink, bath or shower trap;
- fixing a running toilet by replacing a fill valve or flush valve;
- resealing a bath or shower;
- replacing a shower head or hose;
- fitting a washing machine to an existing valve;
- insulating pipes in lofts and garages.
These jobs involve existing connections, can be isolated easily, and rarely cause harm if they go wrong, as long as you turn the water off first.
DIY with care, if you're confident
- replacing a basin or kitchen tap;
- replacing a toilet or basin like for like;
- fitting an outside tap (it needs backflow protection such as a double check valve);
- replacing a radiator or radiator valves, which involves draining the heating system;
- running new pipework with push-fit or compression fittings.
Mistakes here can cause slow leaks that damage floors and ceilings unnoticed. Check joints over the following days, and consider a leak sensor underneath.
Call a professional
- Anything involving gas, including boilers, gas hobs and gas fires. By law, gas work must be done by a Gas Safe registered engineer.
- Unvented hot water cylinders: installation and some maintenance must be done by a competent, qualified person under the Building Regulations.
- New drainage connections and changes to soil stacks, which usually fall under Building Regulations.
- Electrical work in bathrooms, such as electric showers, which needs a qualified electrician.
- Leaks you can't find or stop, leaks inside walls or under floors, and anything with signs of structural damage.
- Soldered joints, if you've no experience with a blowtorch.
- Replacing lead pipes, which may also involve your water company.
A five-question test
- Can I isolate the water (or heating) completely before I start?
- Is it a like-for-like swap rather than a new installation?
- Does it involve gas, electricity, an unvented cylinder or drainage changes? If so, stop.
- If it goes wrong, could water reach electrics or a ceiling below?
- Do I have the right tools and parts, and know what each part does?
If you answer no to either of the first two, or yes to the third or fourth, it's probably a job for a professional.
Know the rules
In England and Wales, the Water Supply (Water Fittings) Regulations 1999 apply to plumbing connected to the mains, whoever does the work. They aim to prevent contamination, waste and misuse. Some installations must be notified to your water supplier before work starts. Scotland has equivalent Scottish Water Byelaws.
Choosing a plumber
- Get two or three written quotes with a breakdown of labour and parts.
- Look for membership of a scheme such as TrustMark or an approved contractor scheme such as WaterSafe, or the CIPHE.
- For gas work, check the engineer's Gas Safe ID card and confirm they're qualified for that type of appliance.
- Ask about guarantees and public liability insurance.
- Be wary of anyone who asks for full payment upfront or pressures you to decide on the spot.
Insurance
Poor DIY work can affect a home insurance claim if it's found to be the cause of damage. Some policies exclude damage from faulty workmanship. Keep receipts for professional work, which also helps if you sell.
Frequently asked questions
Can I replace my own boiler?
No. It's gas work and must be done by a Gas Safe registered engineer, and the installation must be notified under Building Regulations.
Is it legal to fit my own bathroom?
Usually yes for the plumbing, provided you follow the water fittings rules, but electrical and drainage work may need professionals or Building Regulations approval.
Sources and further reading
- Gas Safe Register
- WRAS: Water Regulations Advisory Scheme
- WaterSafe: Find an approved plumber
- TrustMark: Find a tradesperson
- GOV.UK: Building regulations approval
Facts checked on 20 October 2026. Spotted an error? Tell us and we will correct it.