How can I soundproof a noisy water pipe?

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If it is the usual small diameter water pipes the best way to reduce the noise from it is to first ensure it is properly fixed to reduce noisy vibration from the movement of water then box it in with a double layer of high density acoustic plasterboard with the space filled with normal loft type fibreglass insulation. For an improved result, our 2mm SBM5 soundproofing mat can be sandwiched between the layers of plasterboard and if possible, lagged around the pipe as well.