Plumber Hughesdale VIC 3166 – Continuous Flow Hot Water System Replaced Properly

Overview of the Problem – Intermittent Hot Water and Burner Cut-Outs

At a property on Freda Street in Hughesdale VIC 3166, our team at Your Choice Plumbers was called out after the homeowner reported that their hot water was no longer reaching a consistent temperature.

The home’s existing unit was a 15-year-old Rinnai 20 continuous flow system, and the owners had started noticing the gas burners cutting in and out at random intervals. In practical terms, this meant the shower would suddenly run hot, then cold, then hot again, creating those frustrating “slugs” of cold water that make the system unreliable to use.

This is exactly the type of situation where homeowners start asking, “why does my continuous flow hot water keep going cold?” or “is my hot water unit repairable or does it need replacing?” As an experienced plumber Hughesdale, we often find that intermittent burner cycling on older continuous flow systems can point to electronic control failure rather than a simple plumbing blockage.

Why This Needed Proper Diagnostic Testing First

Before recommending replacement, we carried out a structured diagnostic process to determine whether the existing unit could still be repaired economically.

That matters, because with hot water systems we always want to confirm:

• whether the fault is electrical, hydraulic, or electronic
• whether the issue is something serviceable
• whether the age of the unit makes repair uneconomical

This is something we often explain on hot water system repairs jobs, because not every inconsistent hot water problem means the whole unit has failed — but older systems do need to be tested properly before decisions are made.

H2: Checking the Power Supply and Filters First

The first step was to rule out the simpler causes.

We checked whether the unit was receiving a stable power supply by testing it on an alternative electrical circuit. The issue remained, which ruled out an unstable incoming power source.

We then removed and cleaned:

• the cold-water inlet filter
• the hot-water outlet filter

Blocked filters can sometimes reduce water flow enough to cause sensor or ignition problems on continuous flow systems. However, even with those filters cleaned and the unit tested again, the burner cycling fault was still present.

That told us the issue was deeper than a maintenance-related flow restriction.

Why the 15-Year-Old Unit Was No Longer Economical to Repair

Once the simpler electrical and flow-related causes had been ruled out, the remaining fault pattern pointed toward the unit’s electronic motherboard.

Given the age of the appliance and the intermittent burner cut-out behaviour, it was clear the internal control board had reached the end of its functional life.

At around 15 years old, that type of motherboard failure generally makes a continuous flow unit uneconomical to repair because:

• the control fault is intermittent and unstable
• the core electronics are already at end of life
• the owner may still face further age-related issues even after repair
• replacement gives much better long-term value and reliability

So although we always test first, this was a clear case where replacement was the smarter recommendation.

Installing a New Continuous Flow Hot Water System

To provide the homeowner with a proper long-term solution, we supplied and installed a new:

Thermann 20 Continuous Flow Hot Water System

This unit was sourced from Reece Plumbing Oakleigh and was pre-set to 50°C, which made it suitable for safe and compliant hot water delivery in the home without requiring a separate tempering valve for this application.

That gave the owner:

• a modern new unit
• reliable burner control
• stable outlet temperature
• improved long-term confidence in daily hot water performance

Using the Correct Valve Kit for the Installation

To ensure the installation was completed cleanly and reliably, we also used a:

Zetco Heater Kit (W20 Flared Water + G20 Flared Gas)

These kits are specifically suited to continuous flow hot water systems and provide a much neater and more dependable connection arrangement for:

• gas flow control
• water isolation
• serviceability
• long-term installation quality

This was an important part of the job because a new heater performs best when the surrounding connection hardware is also properly matched to the appliance.

Commissioning and Testing the New System

Once the new Thermann unit was installed, we fully commissioned the system and tested it under live operating conditions.

We ran multiple outlets at the same time to confirm:

• stable burner operation
• consistent hot water delivery
• no temperature drop-outs
• reliable performance under normal household demand

The new system delivered a steady, uninterrupted flow of hot water, which was exactly what the owners had been missing with the old failing unit.

Why Replacement Was the Right Call on This Job

This case is a very good example of why systematic testing matters.

The owners did not want to replace the unit unnecessarily, and neither did we. But once the testing ruled out:

• power supply issues
• blocked filters
• simpler service faults

it became clear the ageing unit had reached the point where replacement was the only practical long-term option.

That meant the final recommendation was based on evidence, not guesswork.

Final Result and Client Outcome

Once the works were complete, the homeowner had:

• a new Thermann 20 continuous flow hot water unit
• stable and reliable burner operation
• no more random temperature drop-outs
• safe pre-set 50°C hot water delivery
• a proper continuous flow valve kit installed
• a much stronger long-term hot water solution for the home

The owners were very pleased that the issue had been diagnosed methodically and that the replacement was only recommended once it was clear the old unit was genuinely beyond economical repair.

Compliance with Australian Standards

This case related directly to the installation and safe operation of a continuous flow heated water service, with hot water delivery needing to align with the relevant requirements under AS/NZS 3500.4 for domestic hot water systems.

In practical terms, this meant the solution was not just about replacing a faulty appliance. It was also about ensuring the replacement system was installed with the correct connection hardware and delivered hot water at a safe and suitable temperature for the home.

All work carried out by Your Choice Plumbers is completed in accordance with the relevant plumbing and gas installation standards so hot water system upgrades are safe, reliable, and properly commissioned.

Our Home Plumbing Experts Approach

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

We include our complimentary Property Protection Audit with plumbing services to help homeowners understand hidden risks like excessive water pressure, unsafe hot water temperatures, and ageing flexible hoses before they turn into emergencies.

Find out more about our hot water system repairs and temperature control valve services where hot water performance and delivery safety need to be assessed together.

Looking for a Plumber in Hughesdale?

If you’re dealing with a continuous flow hot water system that keeps going cold, burner cycling issues, or want honest advice on whether repair or replacement makes more sense, visit our Plumber Hughesdale page to learn more about how we help local homeowners.