Plumbing Valve Buying Guide

Your stopcock is like a control tap for mains water to a property. An external stopcock controls the flow from the street's water main to the home, and is usually located just outside your property. An internal stopcock turns off the water using a plug or stopper as it enters the property and is typically found under the kitchen sink or in a cupboard, bathroom, or utility room. It looks like a tap, minus the spout, acting as a connector between two lengths of pipe.

A ball valve is a device that uses a hollow, perforated ball to manage water flow. When the ball's hole aligns with the flow inlet, it's open. Twisting the valve 90 degrees upwards shuts the valve, blocking the flow. The handle lays flat when open and stands upright when closed, making it easy to visually confirm whether it’s open or not. Ball valves are affordable, with various designs available for specific applications.

Gate valves are similar to stopcocks, but are more commonly found in industrial settings. They control the flow using a gate or plate which is moved to shut off or open the valve. They are controlled using a wheelhead at the top of the valve.

Dual appliance tee valves let you connect two machines to one supply pipe, commonly used for washing machines or dishwashers. They simply act as splitters, allowing water to flow to one or both appliances, reducing the need for excessive pipework.

Isolating valves, also known as service valves, are used for stopping water flow to a specific appliance without shutting off the water supply to the entire property. They work in the same way as stopcocks with a lever or screw that is turned to open or shut the water supply. This is ideal for maintenance or repairs, minimising water loss and preventing disruptions to the entire system.

Check valves ensure water flows in one direction, preventing backflow. If the water flows backwards, a ball or disc moves to close the valve. They're crucial for stopping water from flowing backward in a plumbing system.

Pressure reducing valves do exactly what they say – lower and regulate water pressure in a plumbing system. These valves have a diaphragm which constricts to let less water through and reduce pressure, and opens if the pressure needs increasing. A pressure gauge on the valve displays the pressure of the water flowing out of the valve. This helps protect plumbing fixtures and appliances from damage caused by excessive water pressure.

Thermostatic mixing valves blend hot and cold water to maintain a consistent and safe water temperature. These valves have a thermostatic element which expands or contracts depending on the water temperature and moves a piston to let more hot or cold water in to reach the desired temperature. They’re often used with showers and taps to prevent scalding and ensure a comfortable water temperature.

Air admittance valves, or AAVs, rebalance pressure in a soil pipe to normal levels. They allow air to enter a plumbing drainage system when negative pressure develops due to water flow. When the pressure is equalised, indicating no water flow, gravity closes the vent terminal, preventing sewer gases from escaping into a building. AAVs are a flexible venting solution, especially in situations where connecting to an existing venting system is challenging.