The air volume produced between a 1/4-1/3hp rotary and a 1/3 hp rocking piston is similar. The benefit of more air volume increases with the rocking piston as the depth gets deeper than 18ft-20ft. Rocking piston compressors are the best way to go when depths are deeper than 18ft. Rotary vane depth pumping limits are 18-20 ft.
Cary and I are not talking about standard piston compressors. We are talking about rocking piston compressors which are different than a standard piston air compressor. Rocking piston compressors have a rubber cup type diaphragm/piston/s versus a piston compressor that has a metal piston with compression rings similar to a car.
Rebuild intervals for rotary vane pumps are based on primarily two features. Pumping depth (max operating presure) and running time. The vanes have an hour-life running time on them (10,000hrs) and this can be extened by decreasing the depth that the pump has to push air to. The higher the air pressure the harder the vanes grind against the metal rotor cavity. A shallower depth of the diffuser (max pond depth) and less pressure to relese air results in longer vane life. A lot of my clients in the north, only have to run their aerators 3 to 8 hrs per day, thus 10,000 to 14,000 hours for vanes takes 6 to 8 years or more. Some guys with smaller shallower ponds have gone 10 yrs and still running on their first set of vanes. It all depends on run time and maximum pressure during operation. 24/7 compressor run times at 18 ft deep and vanes may last only about 13-16 months. Replacing vanes is a very simple job and takes about 15-20 minutes; 30 minutes max. Replacing the rubber cups on a rocking piston compressor is I think quite a bit more difficult than replacing vanes.
