First, check whether low pressure affects the whole house or just one tap, shower or appliance. Clean the affected tap’s aerator or showerhead, and check that the main stop tap near the water meter is fully open. Look for visible leaks, damp areas or a suddenly changing water meter, and contact your water provider if the issue appears to affect the street supply. If the problem continues, or involves hot water, a pressure-reducing valve or possible leak, have a licensed plumber investigate rather than adjusting valves yourself.