The various valves used in plumbing to control and isolate supplies are usually made from brass – hence the term brassware when looking through catalogues. Some are chrome plated as well but this is really a cosmetic enhancement and these are mostly used where they will show. The purpose of these valves is to allow maintenance and repair work on the plumbing without draining the whole system down.
As with all isolating valves, it is good practice to check their operation at regular intervals to prevent them from seizing up. Finding a valve that won’t turn always seems to happen when it’s urgent. Switching them off and then on again every now and then should keep them in good working order.
Stop valves are primarily used where the water pressure is high. A common example is usually found on the incoming mains water supply into your house. Usually located near where the supply comes into the property this stop valve will switch off the supply to the whole house. It doesn’t mean that all water will stop flowing though! If you have a cold water storage cistern, this will already be full so turning off the water at the mains stop valve won’t have any effect on that until the water in it has been used up. It is always a good idea to locate and label your incoming mains water stop valve so that you can find it quickly in case of an emergency.
Inside the valve body, a rising spindle with a jumper and washer at the base is used to close off or open the flow of water within. The washer and jumper arrangement sits over an opening and stops the water supply by closing this opening. The rising spindle is mounted in the headgear and is sealed at the top by means of a packing gland nut. This gland can weep on old fittings where the packing has become worn. This can sometimes be resolved by tightening the nut a little or, if needs be, repacking it.
These are different in appearance and internal design to the stop valve. They have a small wheel on the top of the spindle and this screws a wedge-shaped gate in or out to close or open the supply line. Unlike the stop valve, the gate moves in or out of the supply line rather than over an opening. The spindle on a gate valve doesn’t move up and down. Instead, the gate itself moves up and down the screwed thread at its base.
Gate valves are normally installed on low pressure supplies and a common example is found on the outlet from the cold water storage cistern. This can be used to isolate the supply of cold water to the various cold water taps in the house which are served by this cistern. If you are replacing a cold tap in the bathroom, for example, this will be the valve that you use to stop the water – assuming the tap is fed by the cold water storage cistern and is not fed directly from the main.
Not to be confused with a ball cock or float valve which is used to control the supply of water to a cistern. The ball valve, or isolating valve as it is sometimes called, has a ball with a hole through its centre mounted in the supply line. The ball can be turned either by a lever or by a small screw head attached to it. The ball can be turned 90 degrees allowing for the water to flow or not. When the hole through the ball is in line with the pipework, the water flows and when the hole is at right angles the water is closed off. This makes it easy to see whether the valve is open or closed by checking whether the lever or screw head slot is in line with the pipe or across it.
A common example of a ball valve can be seen on the supply to a washing machine. The valve will be mounted before the flexible hose connection and allows for easy isolation of the water when removing the machine or changing the hoses.
The drain valve, as its name suggests, allows for draining down a plumbing system or section of pipework. The valve has an outlet point which is opened or closed by a washer and jumper arrangement inside the body. This is turned using a wrench or spanner making it less likely to get opened inadvertently. When using the valve, a hose may be connected to the outlet and secured with a jubilee clip to minimise the chance of a leak. When the valve is opened, water from the system flows from the outlet to a suitable drain point via the hose.
A common example is the drain valve fitted on the radiator pipework in a central heating system. If you are changing a radiator or flushing the central heating pipework, this is the valve you will use to empty the pipes. Drain valves should always be fitted at the lowest point in the system so that all water can be drained off.