Low Hot Water Pressure? Causes & Fixes
Low hot water pressure — a weak hot tap when the cold runs fine — usually points to a pressure limiting valve, a blockage, or a tempering-valve issue. Here's how to tell which, and how we restore it.
Why your hot water pressure dropped
When hot pressure is low but the cold tap runs strong, the problem is on the hot side — not your mains. The usual culprits are a failing pressure limiting valve (PLV) that's over-restricting flow, sediment or scale blocking the hot lines or the tempering valve, or a tank/valve issue specific to the hot outlet. A sudden hot water pressure drop across the whole house points to a valve; a slow decline at one tap points to a blockage or aerator.
Low hot water pressure is nearly always a repairable valve or blockage rather than a new system — the key is isolating where the restriction is.
What's probably causing it
Ranked by how often we see it — tell us which sounds like yours and we'll come prepared.
Pressure limiting valve (PLV) failing
The PLV protects the system by capping incoming pressure. When it fails it often over-restricts, dropping hot pressure across the home — a common, replaceable cause.
Sediment or scale blockage
Mineral build-up in the hot lines, tempering valve or tap aerators restricts flow on the hot side only.
Tempering valve restriction
A partly blocked or failing tempering valve chokes the blended hot water, cutting pressure at the tap.
Tank or outlet issue
On some systems a failing outlet or a corroding tank can restrict hot flow specifically.
Isolation valve not fully open
A partly closed isolation valve on the hot side — sometimes after other work — quietly limits pressure.
Usually a valve replacement or a cleared blockage — a straightforward repair.
What's safe to check — and what isn't
A few checks are safe for anyone; the rest is a licensed gas or electrical job.
What's safe to check yourself
- Is pressure low at every hot tap, or just one?
- Does the cold tap run at full pressure?
- Clean a single tap's aerator and retest
- Any recent plumbing work that may have left a valve part-closed
Pressure and tempering valves are a licensed job — don't adjust them yourself.
When to call a licensed pro
- Low hot pressure across the whole house
- A sudden drop in hot pressure
- Any pressure-limiting or tempering-valve work
- Suspected blockage in the hot lines
Valve replacement and line work must be done by a licensed plumber.
How we restore your hot water pressure
The licensed repair, and the fastest path back to hot water.
We test the pressure limiting valve, tempering valve and hot lines to find the restriction, then quote the fix — usually a valve replacement or clearing a blockage. A failing PLV is one of the most common causes and a straightforward replacement. If it's widespread scale, we'll advise on the system and water conditions too.
Pressure limiting valves do an important job — our pressure limiting valve guide explains what they do and when they need replacing.
See also: book a repair · about pressure limiting valves
Low Hot Water Pressure? Causes & Fixes questions, answered
If yours isn't here, call — the line's attended 24 hours.
Why is my hot water pressure low but cold is fine?
What causes a sudden drop in hot water pressure?
Can I fix low hot water pressure myself?
What is a pressure limiting valve?
Is low hot water pressure expensive to fix?
Do you fix low pressure the same day?
Tell us what's happening — we'll fix it
Call the 24-hour line with your suburb and the symptom, or request a quote. We prioritise no-hot-water call-outs and come prepared with the likely parts.