Hot Water Not Hot Enough? Why It's Lukewarm
Hot water that's only lukewarm — warm but never properly hot, or running cold fast — usually points to a tempering valve, a part-failed element or thermostat, or a system that's undersized for the household. Here's how to tell which.
Why your hot water is only lukewarm
When hot water is not getting hot — lukewarm at best, or hot then cold within a minute — the heat is either not being made or not being delivered. A failing element or thermostat heats the tank only partway; a drifting tempering valve (which blends the hot water down to a safe temperature) can send it too cool; and a tank that's undersized or whose dip tube has failed runs out of genuinely hot water fast.
Lukewarm hot water is usually a straightforward repair — a valve, element or thermostat — rather than a new system. The trick is diagnosing which, which is what we do on site.
What's probably causing it
Ranked by how often we see it — tell us which sounds like yours and we'll come prepared.
Tempering valve drifting
The tempering valve blends hot water down to a safe delivery temperature. If it drifts or fails, it can send the water out too cool even though the tank is hot.
Part-failed element (electric)
On a twin-element electric tank, one failed element heats only part of the tank — so you get some warm water that runs cool quickly.
Faulty thermostat
A thermostat set or failing low heats the tank below temperature, so the water never gets properly hot.
Undersized or exhausted tank
If the household has grown or usage has risen, a tank that's too small simply runs out of hot water fast — more a sizing issue than a fault.
Failed dip tube
A broken dip tube lets cold inlet water mix straight into the hot outlet, so delivered water is lukewarm.
Tempering valve, element or thermostat — usually an affordable fix.
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 it lukewarm at every tap, or just one?
- Does it start warm and run cold fast, or never get hot?
- Has the household's hot water use grown recently?
- Any recent work on the system to tell us about
Tempering-valve and thermostat adjustments are a licensed job — don't raise delivery temperature yourself (scald risk).
When to call a licensed pro
- Lukewarm water at all hot taps
- Hot water that runs cold within a minute
- Any tempering-valve, element or thermostat work
- You want the delivery temperature checked safely
Delivery temperature is set for safety — adjusting it is a licensed job.
How we fix lukewarm hot water
The licensed repair, and the fastest path back to hot water.
We check the tempering valve, element, thermostat and tank behaviour to find why the water isn't getting properly hot, then quote the repair. A tempering valve or thermostat is a common, affordable fix; a part-failed element is a straightforward replacement. If it turns out the tank is simply undersized for your household, we'll talk through the right size rather than chase a fault that isn't there.
Tempering valves are a frequent culprit — our tempering valve guide explains what they do and why they drift.
See also: book a repair · about tempering valves
Hot Water Not Hot Enough? Why It's Lukewarm questions, answered
If yours isn't here, call — the line's attended 24 hours.
Why is my hot water only lukewarm?
Why does my hot water go cold so fast?
Can I turn my hot water temperature up myself?
Is lukewarm hot water an easy fix?
What is a tempering valve?
Should I replace the system if it's not hot enough?
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.