jg74, make sure if you get a rocking piston that it is dual head. Single head rocking piston produces less air than the 1/4 hp rotary vane. Myself, I prefer the rotary vane in your situation of pond depth. Rotary is quieter, and easier & quicker to do the rebuild. If you keep a rotary vane in dry conditions very little annual maintenence is necessary. Most people have problems with rotary compresors due to blatant neglect and allowing occassional moist operating conditions. Operation of rotary for 6-8 hrs a day for 12 ft deep diffuser during the open water season should provide at least 8-10 yrs of service before a rebuild is necessary. Manufacturer of GAST compressors maintains the standard 1 yr warranty. The extended 2 yr warranty is a promotional item from the aerator supplier.
