A guy whose house I was working at the other day commented that his water pressure in the house seemed to have reduced recently. His water supply comes in through a basement and this is where the stop tap is. The run of pipe in the basement is 15mm plastic before it joins to the original lead as it goes under the floor into the kitchen area. We disconnected the pipe in the basement and ran the water and it measured 15lpm. we then reconnected it and tested the flowrate at the kitchen sink which was at best 12lpm when no other outlets were open. We then tested the bath flow rate which only managed 8lpm at best but dropped to 6lpm when the cold tap in the kitchen was opened. Any ideas as to why the flow rate in the house is low compared to the flow rate in the basement and how could we boost the flow rate in the house, especially upstairs.