How to Select a Pressure Regulator

Download a Copy of the Hayward Pressure Regulator Sizing Chart

Pressure regulators can be selected based on the size of the pipe in the system. But they're not like on/off valves, more is involved. Sizing a pressure regulator is a bit more difficult than sizing some other types of valves, but it is not all that hard to do. The first thing you need to do is download a copy of the catalog page that has the Pressure Regulator Flow Coefficients Charts. The chart is at the bottom of Page 2. Click Here to download the catalog page.

Three Things to Know to Properly Size a Regulator

OK, now that you've downloaded the chart we're ready to go. You will need to know three things to properly size a regulator for an application. You need to know what the inlet pressure is going to be into the regulator, what pressure is to be set at (this will be the required downstream pressure), and how much of a flow rate is required downstream.

Determine What Size Hayward Regulator is Required

Once you've got this information you can begin to determine what size Hayward regulator is required. The theory behind sizing a regulator is to calculate the pressure drop across it at the required flow rate and compare it to the required pressure drop (the difference between the set pressure and the inlet pressure). If the pressure drop across the regulator is equal to or less than the required pressure drop, the application is a good one.

For example, let's say you have an application that requires a downstream pressure of 30 psi. The inlet pressure is 50 psi, a flow rate of at least 10 gpm is required downstream and the system pipe size is 1". Let's start with a 1" size regulator and see if it will work. We need to find the Cv of the regulator at a set pressure of 30 psi. From the chart you've downloaded you can see the Cv is 5.5 (the intersection of the 30 psi line on the chart and the 1" valve line). The Cv is on the bottom horizontal scale.

Now divide the required flow rate, 10 gpm, by the Cv of 5.5. The result is 1.81. Multiply this number by itself (1.81 X 1.81) and you'll get 3.27. This is the pressure drop across the valve at the set pressure. Since it is less than the required pressure drop of 20 psi (50 psi inlet minus 30 psi set pressure) the application is a good one. If the result of the calculations is over 20, the regulator would be too small and you would have to try the next larger size.

Calculate the Maximum Possible Flow Through It

Another way to see if the regulator will work is to calculate the maximum possible flow through it. On a pocket calculator enter 20 (the required pressure drop) and hit the square root key. You'll get 4.47. Multiply this by the Cv factor of 5.5 and you'll come up with 24.59, the maximum flow rate in gpm through the regulator for this example. Since the application needed at least 10 GPM and the regulator can handle up to 24.59, the application is a good one.

Remember, not all applications are exactly the same and these recommendations may or may not apply for all applications. Investigate all of the application's parameters: temperature, pressure, and chemical compatibility, etc. before reaching a decision on the valve to use.