Bathroom Mixer Tap - Tapping Noise

[AOIS]

I have a Roca bathroom mixer tap, when hot water drains through the trap there is a high pitch tapping noise which sounds like it’s coming from within the mixer or trap itself.

It’s not a knocking noise like the pipe rubbing on stud wall as it’s very a high pitch noise. Sometimes it can be heard when the tap is not even in use.

Any thoughts appreciated.

Thanks

 

[Burger]

You may have an anti-syphon trap, which could be causing the noise,it may have dirt/debris inside and may just want a clean.