Hi - I had a new bathroom installed last December with a separate bath, shower and basin. All of a sudden the pressure within the shower has reduced when the hot water is turned on. The shower runs of the combi boiler and the pressure in both the bath and sink are both fine. The pressure on the boiler also appears to be normal. Would you be able to advise why the pressure would have suddenly dropped in the shower? - Thanks

I assume your mean the flow is reduced, not the pressure. Remove shower head and see what happens.

If this loss in volume or pressure occurs only when you use the hot water then I would suggest that the hot inlet to the shower cartridge is partially clogged. Remove the cartridge and inspect and clean or replace... should resolve the problem.

Mark

Both experts gave excellent advises, If you have problem only with the hot side I agree with Mark and if you have problem with hot and cold do as hkstroud suggested, Good luck.

John

If cleaning shower head or cartridge doesn't help, it may be temperature / pressure balancing mechanism inside your cartridge, that is not working properly. If that is the case, get a new cartridge

Hope that helps

Milo

You mentioned a combi boiler. If you have a new tankless water heater it could be that the tankless heater has a throttling valve on the outlet of the heater to modulate the flow through the heater to maintain the required outlet temperature. The drop in the hot water pressure will cause a corresponding drop in the cold water pressure with a pressure balancing type of shower valve. Many purchasers of tankless water heaters are learning this unfortunate lesson. Tankless heaters are sometimes oversold. As flow increases through the heater (More fixtures being used) the heater compensates by throttling down a valve to try and maintain a constant outlet temperature. Check to see if this may be the issue. May of the tankless heater manufacturers have only a 35 to 50 degree temperature rise. A storage type heater could resolve the issue if that is the problem.