Very loud noise from bathroom tap

[Strawbs11]

I've just had a new bathroom fitted (yay!) and the sink was finally plumbed in yesterday after 10 days out of action. I've just turned on the new tap for the first time this morning and there's a very loud noise when the water (hot and cold) is running. It sounds almost like a blowtorch! When the water is at a dribble speed there's no noise, and when it's on full pelt it's also fine, but when it's running at normal speed it makes the blowtorch noise. We had no issue with the previous taps (which were separate hot and cold).

Could this just be due to air in the system because the pipe hasn't been used for 10 days, or is it another issue?

It's a similar type of tap to this model: www.wickes.co.uk/Wickes-Mirang-Lever-Basin-Mixer-Tap---Chrome/p/161652

Is this something I can fix myself or will I need to get our bathroom guy back? Thanks in advance!

if it's air, it will clear within a day.

Have you got a combi boiler, or a cylinder? What colour?

@pigletjohn Thanks for the reply! I've got a combi boiler. On another forum I was advised to turn the isolator valves under the bathroom sink so they're semi-closed, which I've just done - this has reduced the noise considerably although it's still there a bit. The water pressure is still acceptable for a bathroom sink (it was very strong with the valves fully open!)

Ideally I'd like to eliminate the noise completely - would a pressure-reducing valve be a better solution than leaving the isolator valves half closed? Also, would a better quality tap make a difference? The one I've got cost £99, so it wasn't cheap!

A tap with knobs or capstans that you rotate would probably be quieter, but might not be to your taste. I think it's the water pressure causing the noise, as water squirts through the restricted orifices in the tap.

I expect you still want full pressure in your shower and bathtaps, so it would be expensive to add pressure-reducers to your basin. You would need one on the hot and one on the cold pipe, they are about £50 to £90 each. This Honeywell looks like the old Caleffi, perhaps they bought the brand.

A gate valve on each would reduce the flow and be much cheaper, but plumbers tend not to like them because, when untouched for years on end, they are liable to seize. But I think that wouldn't matter much because once fitted, you will probably have no need to turn them until the basin tap needs replacing, and you could turn off your main stopcock while working. They are about £5 to £10 each. Pegler is a good brand.

I expect most people would rely on the isolator valves and learn to live with it.