When you turn on your faucet, water appears. The water is actually being propelled out of your tap by a force known as water pressure.

Water pressure is usually measured in pounds per square inch (psi) or feet of head (feet). Feet of head can be described as the height to which the water would raise if you poked a hole in the pipe. The King County Health Department and the Uniform Plumbing Code both recommend residential water pressures to be in the range of 30 psi to 80 psi (70 ft to 185 ft). Water pressure within the District’s system is supplied by gravity from the height of the water in our storage tanks. Additional water pressure is gained as you move down hill. Because there is such a change in elevation from the top of the plateau to Lake Sammamish, the District has split the water system into a series of different pressure zones to keep the system pressures in acceptable ranges. However, the range of elevations on the Plateau is so great that water pressures in some portions of the District’s system do exceed 80 psi. When pressures exceed the 80 psi level, the customer is encouraged to use a Pressure Reducing Valve (PRV) on their individual plumbing. A PRV controls the maximum pressure that can occur downstream of the valve. Most PRV’s are located directly behind the District’s water meter, or near where the piping enters your house, often in a garage or crawl space. Plumbers can provide and install PRV’s.

If you think your water pressure is high, and would like to know what your pressure actually is, please contact the District’s Customer Service Representatives. (392-6256)