Quality Pressure gauge 1/4 inch screw-in threadSave time, water and electricity by only doing a backwash and rinse when necessary. These pressure gauges are installed on the MPV of sandfilters and indicates the operating pressure when the pool pump is working. For example, let's say after the filtersand or filter media is clean the operating pressure ius about 7 PSI or 50kPa. As dirty and debris clogs up and gather inside the sandfilter, the operating pressure will increase because of restriction