Generally you should rebuild your pond aerator compressor unit every 3-5 years under normal conditions.  Air filters should be changed or cleaned once or twice a year. 

Pond Aeration Rebuild Kits & Filters

Stratus SRC rocking piston compressors contain these wearable internal components. Like tires on your car, these parts need...
DC22, DC12  Repair Kits If your air compressor runs but does not pump air after a couple years...
ERP rocking piston compressors contain these wearable internal components. Like tires on your car, these parts need to...
Rotary vane compressors each have four self-wearing vanes, when worn they no longer catch air resulting in reduction...
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