09/02/2022
Something that plumbers might find interesting is that when you drain a geyser in a high rise building you get what is called siphonic action. What this means is that when the system is drained, the water in the pipes can weigh in excess of 1 ton, and the gravity can suck the water out of the geyser, which can start to crumple the cylinder.
The vacuum breaker (which is essentially a one-way valve) lets air into the hot water cylinder or system, which equalizes the atmospheric pressure inside the cylinder and prevents the crumpling effect (siphonic action).
The other function that a vacuum breaker performs is that when it is installed (300mm above the geyser - one above the cold water inlet and the other on the hot water outlet) what can happen with focus mixers is that they shut the water off very quickly so you will get hydraulic shock. This happens because the water compresses in the pipe has nowhere to go. In simple terms, it shocks the system.
A vacuum breaker acts as a shock absorber by allowing the air to compress in the upstand pipe just below the vacuum breaker. This protects water systems and especially geysers from this shock action.
