At a home on Morotai Avenue in Ashburton VIC 3147, our team at Your Choice Plumbers was called out after the homeowner reported very poor water flow throughout the house.

The issue had become serious enough that showering was difficult, and because a newer heat pump hot water system had recently been installed, the homeowner understandably suspected the hot water unit itself might be causing the problem.

What made this case unusual was that it combined two opposite symptoms at once: the household had very low flow at the fixtures, yet the property was still operating under excessively high mains pressure.

This is exactly the sort of situation where homeowners start asking, “why is my water pressure low if the mains pressure is actually high?” or “can a faulty pressure regulating valve cause both poor flow and compliance issues?” As an experienced plumber Ashburton, we know these types of jobs need proper diagnosis rather than guesswork.

The Problem – Low Water Flow in a 15-Year-Old Home

The homeowner’s main concern was simple: water flow in the home had dropped to the point where everyday use was becoming frustrating.

Low flow issues like this can sometimes be caused by:

  • a restricted fixture
  • a faulty valve
  • a partially blocked line
  • a hot water unit issue
  • or a failing pressure control device

Because the home also had a newer heat pump hot water system, that appliance was an obvious first suspect. But on jobs like this, the most important thing is to test the system step by step rather than assume the newest appliance is the cause.

First Step – Ruling Out the Heat Pump Hot Water System

We began by checking the heat pump hot water system and confirming that it was not restricting the water supply.

This was an important first step because it allowed us to rule out the newer appliance and shift attention back toward the incoming water service and pressure control setup.

Once the hot water system was cleared as the cause, the next step was to test the mains pressure properly.

Pressure Testing Revealed a Major Compliance Problem

When we connected a gauge at the front garden tap, the static pressure reading came back at 900 kPa.

That was a major finding.

Under AS/NZS 3500, domestic water pressure should not exceed 500 kPa, so this home was operating at almost double the safe recommended limit.

At this stage, the job became very interesting because the homeowner was experiencing low usable flow, but the pressure test showed the home was actually under very high pressure.

That told us the issue was not a weak supply from the street. Something in the system was clearly restricting volume while also failing to regulate pressure.

The Real Diagnosis – A PRV Failing in Two Different Ways

The existing Pressure Regulating Valve (PRV) had been installed when the house was built, and it had reached the point where it was no longer doing its job properly.

Instead of regulating the incoming mains to a safe level, the old valve had developed a dual failure:

  • it was no longer limiting pressure
  • and it was also acting as a choke point, restricting the water volume moving through the supply

That is why the homeowner was seeing what felt like poor pressure at the fixtures, even though the actual system pressure was dangerously high.

This is a very important distinction.

In practical terms, the home did not have a supply shortage. It had a failed valve creating poor flow conditions while still exposing the entire plumbing system to excessive mains stress.

Proving the Fault Was in the PRV

To confirm the diagnosis clearly, we demonstrated the problem on site.

We disconnected the old PRV and turned the water meter stop valve to the open position. Once that was done, a strong, unrestricted volume of water came directly through from the meter.

That test proved the fault was not in:

  • the street supply
  • the internal pipework
  • the heat pump hot water system
  • or the household fixtures

The failing PRV itself was the restriction point.

This type of demonstration can be very helpful for homeowners because it turns a confusing plumbing symptom into something visible and easy to understand.

Why Replacing the PRV Was Essential

At this point, the old PRV needed to be replaced immediately for two reasons.

To Restore Proper Household Water Flow

The failed valve was choking the supply, which meant taps, showers, and general water use could not perform as they should.

To Bring the Property Back Into Compliance

At 900 kPa, the home’s plumbing system was under significant ongoing stress. That level of pressure can contribute to:

  • leaking taps
  • toilet valve wear
  • flexi hose failures
  • burst pipes
  • appliance connection damage
  • reduced life of plumbing fixtures across the home

So this was not just a comfort issue. It was also a broader property protection issue.

This is why pressure regulating valve installation is often one of the most important prevention upgrades on Melbourne homes with older plumbing setups.

Installing the New Pressure Regulating Valve

We replaced the failed PRV at the water meter with a new valve suited to the home’s water service requirements.

Once installed, the results were immediate:

  • household flow returned properly
  • taps and showers regained normal performance
  • the mains pressure was brought back under control
  • the home’s plumbing system was no longer being exposed to 900 kPa stress

This meant the solution delivered both:

  • better day-to-day usability
  • and better long-term system protection

The Result – Flow Restored and Home Protected

Once the work was complete, the homeowner had:

  • strong water flow restored throughout the home
  • a failed PRV removed from the system
  • water pressure brought back to compliant conditions
  • better protection for all internal plumbing fixtures and appliances

What had originally seemed like a mysterious low-pressure problem turned out to be a classic example of why good plumbing diagnosis matters. The visible symptom was poor flow, but the true cause was a pressure control device failing in a way that most homeowners would never suspect.

Why This Job Matters

This case is a strong example of why pressure and flow should never be judged by feel alone.

Many homeowners assume that low flow automatically means low supply pressure. But in reality, a failed PRV can create the exact opposite scenario — high mains pressure combined with poor usable household flow.

That is why proper testing matters so much on jobs involving:

  • low water flow
  • inconsistent pressure
  • ageing valves
  • newer appliances being blamed unfairly
  • and broader property protection concerns

It is also why this type of job sits naturally between pressure regulating valve installation, hot water system diagnosis, and general home plumbing troubleshooting.

Our Home Plumbing Experts Approach

At Your Choice Plumbers, we focus on both repair and proper diagnosis.

In this Ashburton job, the homeowner could easily have been left chasing the wrong cause or replacing the wrong equipment. Instead, by testing the system properly, we were able to identify the real issue and provide a fix that solved both the immediate symptom and the wider compliance risk.

That is the difference between replacing parts blindly and solving the plumbing problem properly.

Need a Plumber in Ashburton?

If you are dealing with low water flow, suspect a faulty PRV, or want to know whether high mains pressure is putting your plumbing at risk, visit our Plumber Ashburton page to learn more about how we help local homeowners.

You can also learn more about our pressure regulating valve installation and hot water system repairs services.