What Is Water Pressure?
Water pressure is the force at which water flows through your pipes, measured in kilopascals (kPa). It determines how fast water comes out of your taps, how well your hot water system performs, and whether appliances like dishwashers and washing machines get adequate supply. In Australia, the standard acceptable range for residential properties is between 150 kPa and 500 kPa, with most plumbers targeting around 300–350 kPa for optimal performance without stressing fittings and appliances.
Melbourne's mains water pressure varies across the city — properties in lower-elevation areas close to water mains typically receive higher pressure, while elevated properties or those at the end of long supply lines may receive lower pressure. Mains pressure can sometimes reach 800 kPa or more, which is why pressure limiting valves are required under Australian standards when mains pressure exceeds 500 kPa.
What Is a Pressure Limiting Valve (PLV)?
A pressure limiting valve (PLV), also called a pressure reducing valve (PRV), is a device installed on the main supply line entering the property that reduces incoming mains pressure to a safe operating level. Under AS/NZS 3500 — the Australian plumbing standard — a PLV is required if supply pressure exceeds 500 kPa. PLVs are typically set to deliver 350–500 kPa to the property's internal plumbing.
PLVs are mechanical devices with a lifespan of roughly 10–15 years. When they fail, they can either stick open (causing high pressure to pass through unchecked) or stick closed (causing abnormally low pressure). A failed PLV is one of the more common causes of both sudden pressure changes and appliance failures.
A plumber can check your water pressure with a pressure gauge in under five minutes. You can also buy a basic gauge at a hardware store and attach it to an outdoor tap yourself — it's a simple push-fit or thread-on fitting. A reading above 500 kPa consistently means you need a PLV or your existing one needs replacement.
Signs of High Water Pressure
High water pressure is often silent until it causes damage. Common signs include taps or toilets dripping after use (pressure forcing water past seals), banging pipes when taps are closed quickly (water hammer), appliances wearing out faster than expected, and hot water systems dripping from the temperature and pressure relief valve. Consistently high pressure accelerates wear on every fitting, joint, and appliance connected to your water supply.
- Taps dripping after being turned off
- Banging or knocking pipes (water hammer)
- Hot water system T&P valve dripping
- Washing machine hoses failing prematurely
- Toilet cisterns running or slow to fill
Signs of Low Water Pressure
Low pressure is typically obvious — weak flow from taps and showers, slow-filling cisterns, and hot water systems that struggle to maintain temperature or flow rate. A continuous flow (instantaneous) hot water system is particularly sensitive to supply pressure; insufficient pressure can cause the system's flow sensor to fail to trigger, resulting in cold water. Low pressure affecting the whole house points to an issue with the mains supply, the property's main stop valve, or a failing PLV. Low pressure at just one outlet is usually a blockage in the aerator or tap cartridge.
Pressure Limiting Valves — When to Replace
If your PLV is more than 10–12 years old, or if you're experiencing pressure swings, it's worth having it tested or replaced as preventive maintenance. PLV replacement is a straightforward job that takes around an hour — supply and installation combined typically costs a few hundred dollars and can save significantly more in appliance damage and water waste from high-pressure leaks. Under Victorian plumbing regulations, PLV installation must be performed by a licensed plumber.
- PLV over 10–12 years old — consider replacement
- Pressure fluctuating during the day — PLV may be failing
- Pressure consistently above 500 kPa — PLV required by code
- New appliance installation — check pressure is within spec first
Pressure Issues or Need a PLV Installed?
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