Replace a Compression Fitting — Trade Method
Replacing a compression fitting is a 30–60 minute job with the right kit and confidence to isolate the water. This is the exact sequence UK plumbers use — including the pressure-test step DIY guides usually skip.
Step-by-step method
1. Cut pipe square, deburr, and clean 15mm of the pipe end
Cut pipe square, deburr, and clean 15mm of the pipe end.
2. Slide the nut onto the pipe, then the olive
Slide the nut onto the pipe, then the olive.
3. Insert pipe fully into the fitting body
Insert pipe fully into the fitting body.
4. Hand-tighten the nut, then 1 to 1
Hand-tighten the nut, then 1 to 1.25 turns with a spanner — no more or you'll cut the olive.
5. Pressurise and check for weeps
Pressurise and check for weeps.
Frequently asked questions
Do I need a plumber to replace a compression fitting?+
Not legally — compression fitting replacement is not notifiable. But if you cannot confidently isolate the water, get a quote (typically £70–£140).
What size compression fitting do I need?+
UK domestic standard is 15mm compression tails. Check your existing fitting first — some older builds use 22mm or imperial 1/2" BSP.
Is the new part guaranteed?+
Reputable brands (Reliance, Pegler, JG Speedfit) offer 5–25 year guarantees on their fittings when installed to instructions.