Overview of the Problem – Water Spraying from the Side of an Aquamax Unit

At a property on Wembley Grove in McKinnon VIC 3204, our team at Your Choice Plumbers was called out after the homeowner noticed water spraying from the side of their Aquamax 390 SS outdoor gas hot water system.

For the owner, the immediate concern was whether the whole hot water unit had failed and would need full replacement. That is a reasonable fear when water is escaping directly from the side of the heater body, especially on a premium stainless steel system.

This is exactly the type of situation where homeowners start asking, “has my hot water tank split?” or “can a leaking Aquamax hot water unit be repaired without replacing the whole system?” As an experienced plumber McKinnon, we often find that certain hot water systems have very specific known failure points, and diagnosing the actual component involved can save the homeowner from unnecessary replacement costs.

Why the Aquamax 390 SS Needs Specific Product Knowledge

The Aquamax 390 SS is not the same as a basic storage hot water system with generic components.

This model has a specific internal arrangement that includes an integrated hot and cold water mixing spindle housed in the side of the unit. That means when water starts leaking from this section, the problem may not be the tank body itself at all.

In this case, understanding the known design weakness of the model was the key to diagnosing the issue correctly.

This is something we often explain on hot water system repairs jobs, because product-specific knowledge can make the difference between a targeted repair and an unnecessary full hot water replacement.

Confirming the Real Fault – Mixing Spindle Failure

Once we inspected the unit, we confirmed the leak was being caused by the well-known Aquamax mixing spindle failure.

The spindle on these systems is made from plastic and sealed with a rubber component inside a brass housing. Over time, the plastic becomes brittle and can snap within the assembly.

When that happens, the seal fails and the system begins leaking under pressure from the side of the unit.

So in this case, the leak was not being caused by a split tank. It was being caused by a failed internal spindle component inside the Aquamax housing.

Why This Repair Was High-Risk and Technically Difficult

Although this type of repair can save the entire hot water system, it is not a simple parts swap.

Even when the incoming water supply is isolated, the Aquamax 390 SS still holds a large volume of hot water in the storage tank. In this case, the unit had around 155 litres of stored hot water, which meant residual head pressure continued forcing very hot water out of the spindle housing during the repair.

That created two important challenges:

  • the repair had to be carried out while scalding water was still discharging from the opening
  • the internal housing had to be cleaned precisely so the new spindle could seal properly

This is exactly why this type of hot water repair needs experience and careful handling rather than a rushed attempt.

Extracting the Broken Spindle from the Brass Housing

To begin the repair, we used a small-head Allen key to disengage and extract the snapped spindle from the brass housing.

Because hot water continued discharging throughout the process, we used double-layered disposable gloves to protect our hands while working on the exposed opening.

This stage required care because the broken spindle does not always come out cleanly in one piece.

Cleaning Out the Internal Housing Properly

A major part of this job was not just removing the spindle body, but also cleaning out the fragments left behind.

When these Aquamax spindles fail, the plastic often shatters and leaves small shards embedded against the inside wall of the housing, usually around 2–3 centimetres deep.

We used a precision screwdriver to carefully remove every remaining fragment from inside the brass housing.

That detail mattered because if any plastic remained in the housing:

  • the replacement spindle would not seat correctly
  • the new seal could fail to locate properly
  • the leak could continue even after the part was replaced

This was one of the most important parts of the entire repair.

Installing the New Genuine Aquamax Mixing Spindle

Once the housing had been cleaned thoroughly, we sourced and installed a genuine Aquamax Mixing Spindle replacement from Reece Plumbing Caulfield.

Using the correct genuine replacement part was important here because this is a product-specific repair and the new spindle needed to match the Aquamax assembly exactly.

Once the new spindle was fitted and the housing sealed correctly, the hot water leak was brought under control and the unit could be recommissioned.

Final Testing and Temperature Check

After installation, we tested the system and checked the hot water performance at the fixtures to make sure the mixing ratio was operating correctly again.

This final commissioning stage confirmed:

  • the leak had been resolved
  • the spindle was seated properly
  • the unit was back in service
  • hot water delivery had returned to normal operation

That meant the homeowner was able to keep their existing Aquamax 390 SS in service rather than facing unnecessary full system replacement.

Why This Repair Was Better Than Replacing the Whole System

This case is a strong example of why correct diagnosis matters so much.

At first glance, a leak from the side of a hot water unit often makes homeowners assume the whole tank has failed. But in this case, the problem was confined to a known replaceable component.

By identifying and repairing the failed spindle properly, the owner avoided:

  • the cost of a full new hot water system
  • unnecessary removal and replacement work
  • disruption associated with a major hot water changeover

Instead, the existing premium system was restored to proper operation with a precise component repair.

Final Result and Client Outcome

Once the works were complete, the homeowner had:

  • the leaking Aquamax 390 SS diagnosed correctly
  • the failed mixing spindle removed
  • the housing cleaned and prepared properly
  • a genuine replacement spindle installed
  • full hot water operation restored without replacing the system

The owner was very pleased that the problem could be solved with a specialist repair rather than a complete hot water unit replacement.

Compliance with Australian Standards

This case related to the correct servicing and repair of a domestic heated water unit, together with confirmation of proper hot water delivery after repair in line with the operating principles expected under AS/NZS 3500.4 for heated water services.

In practical terms, this meant the system could not simply be stopped from leaking. The failed internal component had to be replaced properly, the housing cleaned correctly, and the hot water delivery checked afterward to ensure the repaired unit was functioning as intended.

All work carried out by Your Choice Plumbers is completed in accordance with the relevant plumbing and hot water servicing standards so hot water leaks are diagnosed accurately and repaired with long-term practicality in mind.

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 McKinnon?

If you’re dealing with a leaking hot water unit, water spraying from the side of the system, or want to know whether a premium hot water system can be repaired before replacing it, visit our Plumber McKinnon page to learn more about how we help local homeowners.