Pipe Sizing - Tech Talk 2
Incorrect pipe sizing all too often causes unsatisfactory performance. Friction is the culprit. As the volume of air passing through the piping increases, the pressure required to deliver the air also increases due to friction (think of it as wind resistance). Since most aquaculture type aeration systems utilize low-pressure blowers, it is critical that nonrestrictive piping be used.
Pressure loss in air systems can be measured in inches of water ("H2O). The resistance to air flow caused by friction will decrease both the pressure to the air outlet (typically an air diffuser) and the volume of air delivered.
When designing the air system, it is important to add together all of the following: the maximum water depth to which the air is driven, the resistance in the air piping system and the resistance caused by the air diffuser. Our simplified chart can be used as a guide in determining the pressure loss caused by the piping. The blower pressure and air diffuser resistances are published in this catalog. If you are confused, don't worry. Call an AES technician at 407-886-3939 for help.
Example: 4 cfm need to be delivered a distance of 200 feet from a rotary lobe blower. The average line pressure is 3 psi. There are no odd twists or elbows that need to be considered. The minimum diameter of plastic pipe will be 3/4", causing 7.4" H2O resistance or pressure loss. The smaller 1/2" pipe would cause 24.6" of loss, which would probably be unacceptable. A 1" pipe, costing little more than the 3/4", might be an even better choice if there is the possibility of using more air in the future.