Question about Hot Springs Sovereign filters ?

[kurt6137]

I have a question about a Hot Springs Sovereign II (2013) hot tub. Do all 4 filters work ( i mean , are they filtering water) when only the circulation pump is on ?  Or does only the 2nd filter in (with the grey top cap) only filter the water ?   I know all 4 filters are working, when the jet pumps are on, but am curious to how they work, when only the circulation pump is on and ozone.

[Flyonthewall]

the grey capped hollow stemmed filter is plumbed to the circulation pump.  it is the only filter in play when the jets aren't on.  the other 3 handle all the water drawn into the jet pump when it runs.  that's why monthly filter rotation is important.  left in place the grey capped filter will clog way before the other 3.