Both water pressure and flow rate are important measurements for a dependable water supply. Water pressure is the amount of force applied by the water, normally measured in pounds per square inch (psi). Flow rate is the volume of water delivered in a specific time frame, measured in gallons per minute (gpm). For an enjoyable shower both pressure and volume are important. Determining these measurements can be done with some basic tools and a little knowledge.
Find a suitable faucet for the water pressure gauge. The gauge will need a faucet with a threaded end. Possible options include: hose bibb, drain connection on a water heater or a washing machine hot or cold water connection point.
Thread the water pressure gauge onto the faucet until it is finger tight.
Turn on the water supply and read the pressure on the gauge. A typical residential home will have a water pressure between 60 and 80 psi. If the pressure is too high or too low you can install devices to raise or lower the pressure.
Place the 5 gallon pail under the faucet you would like to determine the flow rate for.
Turn on the water fully and start the stop watch at the same time.
Stop the stop watch when the pail is full. Divide the time by the amount of gallons. If it took one minute to fill the 5 gallon pail then the water flow rate is 5 gpm. Different flow rates will be found on different faucets. A number of factors affect the rate including pipe length and diameter, elevation and faucet restrictions.