What causes low water pressure?

Low water pressure can be caused by poor natural head on a gravity system, or an increase in demand ie if more than one outlet is used at the same time, or an extension/ new bathroom etc has been added to a property. On mains fed systems, water pressure will vary throughout the day and at peak demand times a drop in performance may be noticed. Other contributors to low water pressure may include poor plumbing or blocked pipework, blocked filters, bent AV Couplers/ hoses and air in the system.