Quick answer
Different pressure at different taps means the restriction is local rather than on the mains. Scaled aerators, isolation valves under basins that were never fully reopened, and corroded galvanised branch pipes account for nearly all of it. If the incoming supply were the problem, every tap in the house would be equally weak — the variation itself is what tells you where to look.
Common causes
- Scaled aerators and showerheads at individual fittings
- Under-basin isolation valve partly closed after previous work
- Corroded galvanised branch pipe feeding one fixture
- Flow restrictor still fitted in a newer tap or showerhead
- Long or undersized branch run to a distant fixture
- Partly blocked flexible connector behind a basin or mixer
What you can do now
- 1Unscrew aerators and de-scale them in vinegar, then compare flow again
- 2Open every isolation valve fully — turn until it stops, then check flow
- 3Test hot and cold separately at each weak fitting to narrow which side is restricted
- 4Check whether the weak fittings share a branch, which points at the pipe rather than the fittings
- 5Look for a flow restrictor insert in newer taps and showerheads
When to call a professional
If one branch is consistently weak after de-scaling and opening every valve, the pipe feeding it is likely corroded and needs re-running. On pre-1980s galvanised plumbing, weak flow at scattered fixtures is usually the first visible sign that the whole supply run is closing up — worth getting assessed before you pay to re-run one branch at a time.
Typical cost in Johannesburg
Pipe re-run R1,400–R4,500
Indicative ranges only. We provide written, itemised quotes before any work.
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