The ECOHEADS filter is located in the handle of the spray nozzle. It's a permanent filter that simply needs to be scrubbed clean regularly, but shouldn't need to be replaced.
Using an old toothbrush, gently scrub under a stream of running water any sediment accumulated in the mesh. You DO NOT need to disassemble the filter to do this and it is not advised to do so.
Gently push the filter back into the main body of the nozzle and screw it back into the end cover.
It really depends on how dirty your water is. On average, we recommend it at least once a month. But some salons do it every three months and others tackle it once a week.