So rather than hijack a thread - where the OP asked if the filter should be on "filter" or "Recirculate".
These were my thoughts, from practical application on a variety (and sometimes strangely frustrating) equipment setups.
Below is my take on my personal experiences and I'm open to suggestions and am always willing to learn a "better" way, especially if it will save me time and money!
DE with a multiport valve - I use recirculate at the very beginning of shocking because live algae clogs the DE faster than dead algae and I don't want to waste expensive DE.
Sand - I use recirculate at the very beginning because live algae clogs faster than dead algae...Flow stops on several of my pools with sand filters if I set to filter with live algae, straight sand, no DE addition.
Cartridge - rare to find a multiport valve at all - I use a portable submersible pump to mimic recirculate for the above stated reasons and I don't want to have to clean the cartridges constantly. Occasionally there is a pump to waste but that's about it.
Now, I'm not the homeowner in these cases and they don't necessarily want to be bothered with monitoring pressure which is why they hired me. Problem is often I can only visit once a day.
Some DE filters don't have a backwash setting OR a multiport valve and I use the portable pump for those (ie Hayward Perflex).
I follow the shock process THEN start filtering, monitoring pressure and backwashing/recharge/fresh fill. With Cart filters and inground pools that have NO waste valve or anything helpful at all (really, wth! ), vacuuming up the dead algae is my biggest challenge. My easiest method has been to shock using the portable until the majority of dead algae has sunk to the bottom or caught up in nets/baskets and then vacuum and clean the filters as needed (a huge pain for which I charge a premium lol).
All pools should have a waste setting at the very least and ideally a recirculate setting too. Just my unsolicited 2 cents.
I have a special method for vacuuming above ground pools that don't have waste/recirculate settings. People are amazed when they see it. Every time. Its pretty funny.
Eh, sorry for the rambling. Today was a long day and thanks to mother nature I accomplished little.