Frequently Asked Questions
Q. "What does 'DIFFERENTIAL PRESSURE P1 - P2 (psi)' mean?"
A. P1 is the unregulated inlet pressure and P2 is the regulated outlet pressure. The differential between these two numbers will indicate which column to use to determine which valve will work best at the gallon per minute flow rate you wish to use.
Q. "What does 'P2 Variation (Pressure Drop)' mean?"
A. P2 pressure Variation (Pressure Drop) is the amount of pressure loss that will be experienced for the gpm (gallons per minute) flow rate required. For example: If the differential pressure is 25 psi (inlet pressure 70 psi and outlet pressure 45 psi), and you want a flow rate of 15 gpm then the pressure drop through the valve can vary up to 15 psi
Q. "What is water hammer?"
A. Water hammer occurs a lot! It is frequently recognized by a "thump" or "bang", usually throughout the water line (if you have copper pipes, you'll tend to hear the noise throughout the house). Water hammer can be caused by a number of things. Many times a loose washer that is jumping around in the faucet or valve causes it. This can be fixed by identifying which valve is the culprit and fixing the washer. Other times it is simply caused by water traveling at a rapid rate and suddenly being shut off. The best solution for this is to increase the size of the water supply thereby slowing down the water (a larger pipe being able to deliver the same amount of water in gallons per minute at a slower speed). If this is not possible, then many times a water hammer arrestor helps.
Q. "My inlet pressure varies, which reading should I use, the higher or lower number?"
A. Always use the lowest number, this will assure you of meeting your minimum pressure and flow rate requirements.
Q. "In the example above you chose a 1" valve when a 3/4" valve almost meets the requirements?"
A. It is best when sizing for optimal performance that, if the requirements fall between an indicated size, you should choose the larger valve.
Q. "Will these valves also control/limit the gpm flow rate?"
A. No, you will need a flow regulator to control the flow rate.