Overview of the Problem – Hot Water Not Hot Enough

At a property on Wellington Street in Brighton VIC 3186, our team at Your Choice Plumbers was called out after the owner reported that the hot water at the bathroom fixtures was not hot enough.

The client explained that the hot water temperature had noticeably dropped over the previous week or so and had reached the point where she knew it was not going to fix itself.

This is exactly the type of issue where homeowners start asking, “why is my hot water not hot enough?” or “do I need a plumber if my hot water system still works but the water is only warm?” As an experienced plumber Brighton, we often find that when the hot water unit appears to be operating normally but the bathroom water temperature is too low, the issue can often be traced to the tempering valve rather than the hot water service itself.

Checking the Hot Water Unit First

The property had a Rheem Stellar 130L outdoor gas hot water system, which was only around 3 years old.

Before assuming the hot water service was faulty, we ran the correct checks on the unit itself.

We:

  • checked the thermostat dial setting
  • turned the thermostat up to confirm the burners fired correctly
  • confirmed with the owner that the pilot light had not been going out
  • checked the pressure and temperature relief valve discharge

When we opened the temperature and pressure relief valve, the hot water discharging through the 1/2-inch copper line was steaming hot, which confirmed the tank was heating properly and the unit itself was doing its job.

That was a very important clue, because it told us the hot water system was producing sufficient heat — the problem was happening after the water left the tank.

Confirming the Real Cause of the Low Hot Water Temperature

Once we had established that the Rheem Stellar unit was operating correctly, we moved to temperature testing at the fixtures.

Using a handheld thermometer, we checked the hot water output at the bathroom taps and confirmed the delivered water temperature was approximately 40°C.

That temperature explained the owner’s complaint immediately.

In a domestic bathroom setting, the hot water supplied to sanitary fixtures such as showers, baths and basins is required to be controlled so it does not exceed 50°C for scald protection. In this case, however, the issue was that the water was being tempered too low, which meant the bathrooms were no longer getting properly usable hot water.

At that point, we confirmed that the fault was the existing temperature control / tempering valve, which was blending the hot water down to around 40°C instead of allowing correctly tempered 50°C delivery.

Why the Tempering Valve Was the Real Problem

This was a very good example of why a hot water complaint is not always caused by the hot water unit itself.

The existing hot water system had been installed only a few years earlier, but the original temperature control valve had not been replaced at the time of installation.

That was the missed opportunity.

Tempering valves are serviceable components and, as with many plumbing control valves, manufacturers commonly recommend periodic replacement over time. In this case, the older valve was still in service and had now started incorrectly mixing the hot water down too far.

So although the storage unit was heating properly, the owner was still only receiving under-tempered hot water at the bathroom fixtures.

Tempering Valve Replacement and Correct Temperature Setting

To restore the correct hot water delivery, we sourced and installed a new:

Tomson Standard Tempering Valve 15mm

The replacement valve was sourced from Reece Plumbing Brighton.

After installation, we set and tested the valve to ensure the delivered hot water temperature was properly controlled and did not exceed the domestic bathroom safety limit.

The hot water was then delivering at the correct usable temperature again, with the bathroom fixtures safely tempered and performing as they should.

Why Tempering Valves Matter for Safety and Compliance

We explained to the owner that in domestic homes, hot water systems are generally stored at a higher temperature to help maintain safe tank conditions, but the water delivered to bathrooms must be controlled to a safer temperature at the fixtures.

That is the purpose of a tempering valve.

In practical terms, the valve allows the hot water system to do its job properly while still protecting bathroom users from excessive delivery temperatures. If the valve fails or drifts out of performance, the result can go one of two ways:

  • water too hot, increasing scald risk
  • water too cool, making the hot water feel inadequate Before assuming the system itself had failed, we carried out the same checks we use on many hot water repairs Melbourne call-outs to confirm whether the unit was heating correctly.

Outcome and Client Result

  • hot water unit checked and confirmed operational
  • bathroom hot water temperature measured at 40°C
  • faulty old tempering valve identified
  • new Tomson 15mm tempering valve installed
  • bathroom hot water restored to proper temperature
  • system checked for correct safe temperature delivery

The client was very happy to have the hot water issue resolved properly and relieved to know the hot water system itself did not need replacing.

Compliance & Prevention Insight

This case highlights why hot water not hot enough should not always be blamed on the hot water service itself.

Sometimes the unit is heating perfectly well, but the tempering valve is no longer controlling the delivery temperature correctly.

It also shows why replacing or checking temperature control valves during a hot water system upgrade is so important. If an old valve is left in place, it can undermine the performance of an otherwise new and healthy hot water system.

Compliance with Australian Standards

All work carried out by Your Choice Plumbers is completed in accordance with the relevant plumbing standards and code requirements, including the temperature control principles referenced under the Plumbing Code of Australia 2022, Plumbing Regulations 2018, and AS/NZS 3500.4.

In simple terms, this means hot water can be stored at a temperature suitable for system safety, while the water delivered to bathrooms is controlled to a safe maximum temperature for everyday use.

Our Home Plumbing Experts Approach

As part of our Home Plumbing Experts approach, we focus on both repair and prevention.

We offer a Complimentary Property Protection Audit as part of our service, assessing key areas like water pressure, hot water temperature, and flexible hoses — helping homeowners stay ahead of potential plumbing failures and avoid unexpected water damage.

Find out more about our tempering valve Melbourne services.