Three categories are not DIY, and the line is about what fails rather than about difficulty. Everything downstream of a working isolating valve is a different matter.
Electricity in a damp room
New wiring, a new socket, a hard-wired mirror or cabinet, an electric bidet seat where no socket exists. Bathrooms are zoned under national wiring rules, and who may do this work is defined there. It is not a question of confidence.
The pressurised side
Work upstream of the isolating valves — replacing a valve that will not close, altering the supply, anything involving the main. A failure there does not drip; it floods.
Powered waste
A macerator or lifting pump is an appliance that discharges waste water under power, with published limits on lift, run and inlet temperature. Installing one outside those limits is how a room floods, and the installation instructions are the authority.
What is ordinarily within reach
Changing a tap between existing isolating valves, a toilet seat, a hand shower, a hose, a trap, an aerator, a cartridge, a flush or fill valve, and anything that fixes to a wall. Those are the jobs this site is written around.
This does not replace the manufacturer's own instructions. Every dimension, thread size, flow rate, operating pressure, water seal depth and load figure on this page is reported from the manufacturer's own documentation, with its unit written as published, and named as such — none of it is measured here. A flow rate is reported with the pressure the manufacturer measured it at, and is never converted to another pressure, because no conversion exists.
Questions people actually ask
Is fitting an angle valve DIY?
It depends on the state of the outlet it screws onto and on the water being genuinely off upstream. It is the boundary case in this list, and the honest answer is that a corroded thread turns it into a job for someone with the parts and the experience to deal with what comes next.
Does this site give installation instructions?
No. It describes what a product needs and points at the maker's instructions and the rules that apply where you live. A page that paraphrased an installation manual would be wrong more often than it was useful.
Last reviewed 5 September 2026