Water pump in Motorhome

I have a fiat Bessecar motorhome E345(2008), the water pump (Shurflow SUK 0227diaphragm pump is working fine but it is making a noise that sounds a bit like a very fast tapping sound, when the taps are turned on.

Next to the pump is a small container, like a filter when i turn it or move it the noise reduces, however once the taps have been used a few more times the noise increases.

I wanted to know if there is a maybe either a pressure problem or if the van needs to be drained fully and refilled.

We are currently in Spain, new to motorhoming so would really appreciate some advice.

regards

Rob