Low Water Pressure in the House? 7 Causes a Plumber Will Check First

Whole house or just one tap?

The first diagnostic question we ask. One tap = local issue (aerator, cartridge, isolation valve). Whole house = main, PRV, or supply problem.

The 7 causes we check, in order

1. Blocked aerator or shower rose — Melbourne water leaves limescale; soak in vinegar for 1 hour.

2. Partially closed isolation valve at the meter or under the sink (often after recent works).

3. Failing pressure-limiting valve (PLV/PRV) — typical life 8–12 years.

4. Galvanised pipe corrosion — homes pre-1970 with original steel mains.

5. Leak on the supply between the meter and the house (check the meter dial with everything off).

6. Hot water tempering valve seized — pressure fine on cold, weak on hot.

7. Network supply pressure — check with the neighbour; rare but happens during mains works.

Quick checks you can do

Read the water meter, don't use water for 30 minutes, read again — any movement = leak.

Test cold pressure at the outside garden tap (closest to mains).

Compare hot vs cold at the kitchen — different = tempering valve or HWS issue.

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