If you’ve noticed that a boiler is suddenly letting out steam, it’s most likely coming from the boiler relief valve, also known as a pressure relief valve. This is will affect any central heating or heating systems. The boiler relief valve is likely discharging steam and/or hot water for one of the below reasons: The pressure levels inside the boiler are too high The valve itself is faulty and needs replacing Here’s what to do if you are in need of fixing your boiler or combi boiler. At Anglo, we stock a range of boiler relief valves that are perfect for the job.