The PLV pressure limiting valve with 500kPa rating is commonly used to regulate the supply cold water pressure to hot water services including heat pumps, electric, gas storage and solar water heaters across all mainstream brands in Australia such as Rheem, Vulcan, Rinnal, Dux, Aquamax, Thermann, Apricus and Solahart. 600kPa rating PLV is used on some jobs only when a high rating PTR valve is specified for the hot water services.
The 350kPa PLV pressure limiting valve is usually used on caravans, trailers and tiny homes and for small applicances such as washing machines, dish washers and coffee machines. In caravan RV motor home applications, the PLV pressure limiting valves used must have an inbuilt check valve to prevent back flow from the on board water heater tanks, unless an external ball valve or check valve is used.
All Plumbing Online carries brands including APO, AW, Reliance, AVG, Tomson, AW, Nefa and Reflex. The PLV pressure limiting valve regulates the inlet water pressure by employing a sliding piston design internally and creates a pressure drop as the water passes through the valve. This piston design is directional and therefore there is an arrow on each pressure limiting valve body indicating the water flow orientation.
Engineer's Notes
When a PLV pressure limiting valve fails, it is usually caused by the corrosion and debris clogging-up inside the valve body, preventing the piston's sliding actions over its usage life spans. In most cases, the water pressure and flow rate can drop significantly causing an unsatisfying user experience. In less common scenarios, the opposite can also happen and the pressure limiting valve may lose its pressure limiting ability, potentially blowing up appliances with over pressures.
A PLV pressure limiting valve can only limit the dynamic pressure of the passing inlet water. The valve can not regulate a static pressure increase inside a water heater when the water heats up and expands, where PTR and ECV valves must be used instead for the pressure relief.
The 350/500/600 pressure number is a nominal outlet pressure rating under Australian Watermark Standard testing condition with a set inlet pressure. In real world situations, the actual mains supply water pressure can fluctuate and vary greatly from locations to locations. This presents a unique challenge for caravans, as the outlet pressure can drop below 350kPa when at a caravan park with a low mains supply pressure. This a very wide spread complaint across the internet and the PLV pressure limiting valve is actually not faulty. The solution is to use a pressure reducing valve instead the pressure limiting valve, because the pressure reducing valve outlet pressure is adjustable on the spot to suit different inlet pressures as required. Check out my "Caravan Plumbing" product categories and my website Blogs for more details.
