Shock arrester combi boiler

[Matt0029]

I usually fit these on the cold feed to the boiler close to the boiler. But if fitting near the boiler would be unsightly. Would they still be effective fit somewhere else in the cold.feed in the system. Say under the kitchen sink? Thanks

 

[EvilDrPorkChop]

Yes, providing there's no Non return valve after the shock arrestor.

 

[Chuck]

To offer full protection to the boiler it needs to be on the direct route from the source of the shock to the boiler, i.e. not up a side-arm.

 

[EvilDrPorkChop]

To protect the boiler it needs to be on the direct route from the source of the shock to the boiler, i.e. can't be up a side-arm.

Why does it matter? Proving it's on the pipework it's doing the same job no matter where it's located.

 

[Chuck]

Why does it matter? Proving it's on the pipework it's doing the same job no matter where it's located.

Because shocks travel very fast, at roughly the speed of sound in water.

So imagine, for example, a shock pulse created by a washing machine valve shutting at A. It travels along a path to the boiler at B. Let's say there is a tee-junction half-way between A and B with the arrestor some distance up the branch. At the the tee-junction the shock pulse splits with (say) 50% of its energy travelling up the branch and 50% traveling to the boiler. If the arrestor is good it will absorb the 50% pulse that arrives at it but it can't affect the other 50%.

So, the presence of the branch and the shock absorber will help reduce the energy of the pulse that arrives at the boiler but only to a limited extent.

Shocks are counterintuitive because the changes to flows and pressure gradients that one is used to thinking about in plumbing happen, relatively speaking, very slowly compared with the speed of sound, so called 'quasistatic' changes.

 

[king of pipes]

Closest to the boiler as possible would be my choice you are trying to protect the plastic components in the boiler from pressure shocks. Kop