Which solution can help mitigate noise in system pipework caused by expansion and contraction?

The solution that effectively mitigates noise in system pipework caused by expansion and contraction is the use of expansion joints. Expansion joints are specifically designed to accommodate movement within piping systems due to thermal expansion and contraction. When hot water flows through pipes, the material expands and when the flow decreases or cools, it contracts. This movement can produce noise such as creaking or banging, often referred to as "water hammer."

Expansion joints allow for this movement to occur without inducing stress in the pipework, significantly reducing noise levels. They can absorb the changes in length that occur as temperatures fluctuate, preventing the pipes from transmitting vibrations or creating friction against fittings or other structural components.

In contrast, while pipe clips can hold pipes securely in position, they do not accommodate movement due to thermal expansion, which can actually exacerbate noise issues. Cushioned hangers can help reduce vibration transmission, but they do not directly address the issue of expansion and contraction. Soundproofing insulation may reduce ambient noise levels but does not alleviate the mechanical stresses that lead to noise caused by thermal movement in the pipes.