How Does a Combination Valve Work?

Unvented cylinders have greatly changed how UK residents access hot water within their homes. Rather than dealing with low water flow, they help ensure good pressure and excellent flow at all taps, all the time. However, in order to operate safely, unvented cylinders require a number of components. One you may have heard of is the combination valve. What is it and how does it work?

A combination valve is exactly what it sounds like – a valve that combines the function of multiple other valves. It’s a way to simplify and streamline unvented cylinder operation and to make maintenance and repairs easier.

A combination valve usually includes four different types of valves. One of those is the pressure reduction valve, which reduces incoming pressure from the mains to a safe level. Another is the check valve, which prevents water from running out of the cylinder back into the fresh water supply line.

In addition to these two valves, the combination valve will also include an expansion valve. This is a critical component and is designed to help protect the cylinder from over pressure situations and will bleed off water/pressure if dangerous conditions occur.

Finally, your combination valve will usually also contain what’s called a line strainer, which is a piece of mesh that helps prevent debris from entering the cylinder.

While combination valves make maintenance and repairs easier, they can suffer from some problems. For instance, the line strainer can become blocked, which reduces pressure and water flow throughout your home. The pressure relief valve can also fail, as can the expansion valve. When these fail, leaks can develop, which should drip into the catch pan under the cylinder. Finally, a failing pressure reduction valve can cause low pressure at the taps.

The solution to all of these problems is to replace the combination valve, but that is not something you should handle on your own. A plumber certified to work on unvented cylinders can provide your repairs for you.