Most of the homes built within the last 25 years have a Pressure Reducing Valve installed usually right after the main shut-off. The pressure reducing valve has two main functions for residential applications. It regulates areas that have high water pressure levels, down to a range of 30-80 psi. The pressure reducing valve can be adjusted, by tightening the bolt you can increase water pressure. Typically you will have to loosen the nut in order to tighten the screw. When the screw is fully engaged your water pressure will be set at the maximum setting of usually 75-80 psi.
Pressure Reducing Valve and Thermal Expansion
Overland Park now requires thermal expansion tanks to be installed in any home that has a closed loop system. A pressure reducing valve creates a closed loop system because it also acts as a backflow device by restricting water to flow in only one direction.
A typical water heater will be set to heat water to about 125 degrees. At this temperature the water will expand about 3-4% in volume. This process is know as thermal expansion. When thermal expansion occurs in a closed loop system it can sometimes cause the relief valve to start leak. It can also be much harder on your water heater if it is forced to absorb the increased pressure. A thermal expansion tank is designed to absorb this additional pressure that builds up inside of a home.