Hello,
I have a house from the 1950's which had a new electric hot water system installed in 2007. When using the shower we get very low pressure. I have measured the flow rate to be around 1.5 litres per minute. Great for the power bill, not so great on cold winter mornings.
The strange thing is, if the water is being used anywhere else in the house at the same time as you are in the shower the pressure in the shower actually INCREASES. Flush the toilet and suddenly the shower wakes up and the flow rate feels like it has at least doubled. Same thing when using the washing machine or dish washer.
Any idea whats going on?