Most Sydney homeowners worry about low water pressure. High water pressure is the less obvious problem, and in many cases it goes undetected for years while quietly damaging pipes, fittings, and appliances throughout the home. Your plumber Sydney team at All Day Plumbing sees the consequences of long-term high pressure regularly, from prematurely failed tap washers and constantly running toilets to split hoses and burst pipes. Understanding what causes it and how to fix it protects your home and your plumbing investment.
What Is High Water Pressure?
In Australia, residential water pressure is measured in kilopascals (kPa). Sydney Water delivers mains water at pressures that can reach well above 500 kPa in some areas, particularly in lower-lying parts of the network where gravity adds to the pressure head. The acceptable range for residential properties is 200 to 500 kPa. Anything consistently above 500 kPa is considered high and requires management. In some Sydney suburbs, particularly those at the base of hills or near pumping stations, mains pressure can exceed 800 kPa without intervention.
The Main Cause: High Mains Pressure From Sydney Water
The most common cause of high residential water pressure in Sydney is simply the mains pressure delivered by Sydney Water’s network. Sydney Water maintains high pressure in the distribution main to ensure adequate pressure at all properties within a zone, including those at higher elevations. Properties lower in the network receive this full mains pressure, which can be significantly higher than the recommended household range. This is why most Sydney homes are required to have a pressure limiting valve (PLV) installed on the incoming supply line. The PLV reduces the mains pressure to a safe level before it reaches your internal plumbing. A water pressure check Sydney will confirm the actual pressure at your property and determine whether the PLV is functioning correctly.
A Failed or Absent Pressure Limiting Valve
The PLV is the primary protection against high mains pressure reaching your home. When it fails, the full mains pressure passes directly into your property’s pipework without any reduction. PLVs have a typical service life of 10 to 15 years, after which the internal diaphragm and spring mechanism can deteriorate. A failed PLV that is stuck open allows high pressure through. A failed PLV that is stuck closed causes sudden pressure loss. In homes without a PLV at all, usually older properties built before PLVs became standard practice, the full mains pressure is delivered to every tap and appliance in the home.
Thermal Expansion in Hot Water Systems
Hot water systems introduce a secondary high-pressure risk through thermal expansion. When a storage hot water system heats water, the water expands. In an open-style system, this expanded water can flow back into the cold water mains to relieve pressure. In a closed system, where a check valve or PLV prevents backflow, the expanded water has nowhere to go, causing pressure to build within the system. If the temperature and pressure relief valve (TPR valve) on the hot water system is discharging regularly, this is often a sign of excessive thermal expansion pressure rather than a faulty valve. A licensed plumber can assess whether an expansion control valve or a correctly configured system setup is needed.
Booster Pumps Set Too High
Some multi-storey properties and units with pressure booster pumps installed to overcome gravity-related pressure loss at upper floors can develop high pressure problems if the pump is set incorrectly or fails in a fault-open condition. If a booster pump was recently serviced, adjusted, or replaced and high pressure problems have appeared since, the pump output setting should be checked by a licensed plumber.
What High Pressure Does to Your Plumbing
High water pressure is one of the most damaging and least visible threats to a home’s plumbing system. The effects accumulate over time and are often misdiagnosed as unrelated individual failures. Common consequences of long-term high pressure include:
- Tap washers and seats wearing out prematurely: High pressure hammers tap washers every time a tap is operated, causing them to fail far sooner than expected.
- Constantly running or noisy toilets: Toilet fill valves and cistern diaphragms are designed for normal pressure. High pressure causes them to fail or not seat correctly, leading to continuous running.
- Appliance solenoid failures: Dishwashers, washing machines, and hot water systems use solenoid valves that are rated to a maximum pressure. High pressure causes solenoids to fail, often leading to water leaks behind appliances.
- Hose and fitting splits: Flexible hoses connecting to taps, toilets, and appliances are a known failure point under high pressure. A split hose can discharge significant volumes of water in a short time. This is a frequent cause of serious internal flooding in Sydney homes.
- Water hammer: High pressure amplifies water hammer, the banging noise pipes make when taps are closed quickly, which over time loosens pipe brackets and stresses joins.
If you are regularly replacing tap washers, dealing with noisy pipes, or have had a hose split, high pressure may be the underlying cause. A water meter installation Sydney assessment that includes a pressure check will confirm this quickly.
How to Fix High Water Pressure
The solution to high water pressure is almost always a PLV installation, replacement, or adjustment. A licensed plumber installs the valve on the incoming supply line at the meter, sets it to deliver pressure within the 300 to 400 kPa range, and tests the system to confirm the reduction. The job is typically completed in a few hours and provides immediate protection to the entire plumbing system. For properties with thermal expansion issues, an expansion control valve may also be needed on the hot water system. Read our guide on 7 plumbing emergencies that cannot wait to understand the situations that high pressure can create if left unaddressed.
Related Reading
- How to Shut Off Your Water During a Plumbing Emergency
- How Much Does Emergency Plumbing Cost in Sydney?
- Pipe Relining vs. Replacement: Which One Is Right for You?
High Pressure Causing Problems? Call All Day Plumbing
All Day Plumbing installs and services pressure limiting valves across Sydney. We test, diagnose, and fix high pressure issues before they cause serious and expensive damage. Call us now on 1300 071 280.