Press versus compression: what can be buried
Point by point
| Criterion | Press fitting | Compression fitting |
|---|---|---|
| Tooling | press jaws | two spanners |
| Fitting cost | dearer | cheaper |
| Can be buried | yes | no, needs access |
| Servicing | none | re-tighten after the first heat-up, check once a year, re-tighten again if it weeps |
| Speed on site | seconds per joint | about a minute per joint |
| Taking apart | cut it out | undo with a spanner |
| Typical mistake | skipped calibration, or wrong jaw profile | over-tightened and crushed the ring, or under-tightened |
The section shows the difference: press deforms the sleeve for good, compression squeezes a ring — and that ring can be squeezed again.
The jaw profile (TH, U, H, B — every maker has its own) must match the fitting — press tools are not universal.
Use press when
- Anything going into a wall, a screed or a sealed duct: you won't get back to it.
- Many joints in a row — the tool pays for itself in speed over volume.
- Concealed pipework in a flat, where a leak means repairing a neighbour's ceiling too.
Use compression when
- Exposed runs: connections to a radiator, boiler or washing machine.
- A one-off repair or tie-in, where buying press jaws for two joints makes no sense.
- A temporary arrangement that will be taken apart later.
Mistakes that cause leaks
Common questions
Can a compression fitting be buried in a wall?
No. A compression joint is designed to be re-tightened when it starts to weep, and has to stay accessible. Only press, welded or soldered joints go into a wall or a screed.
Do I really have to calibrate the cut before pressing?
Always. The calibrator chamfers the edge and restores the pipe to round — otherwise the edge slices the O-ring and the joint starts weeping months later, from behind the tiles.
Is it worth buying press jaws for a couple of joints?
No: press jaws pay for themselves on volume. For two exposed joints — a radiator tail or a washing machine — compression fittings and two spanners are enough.