Isn't it wrong to spray from the outside of a filter? It would push some of the material deeper into the filter!

No... you are essentially spraying it off not in. The buildup on the outside can't penetrate the filter material. Also there is no effective way to spray from the inside. This is an outstanding product works great and is very well made.

Can someone recommend a faucet adapter. we live in new england so howe’s freeze in winter. the home depot 3/4” didn’t work with our faucets.

Why not do it in your tub inside your home?

Can anyone who has used one of these tell me if they truly have enough pressure?

I've used it twice now. Compared to other places I've lived, I would describe our water pressure as average--neither the best or worst I've seen. I have a Pentair C&C 420 filter with four cartridges. The technique I've found to work well is to start at the top of a filter and "wiggle" the spray from side to side, so that the individual streams can get into each pleat, moving from top to bottom. The 16 streams converge about 4 inches from the tool, so you can use a concentrated hit for stubborn patches (I don't have those any more since I started using skimmer socks.) I don't have a place or time to soak the filters, so I use a light spray of Simple Green before spraying. Works well.

Can I use one of those "colaplasable hoses" with the Filter Flosser?

NO! NO! NO! Collapsible hoses DON'T WORK with this product, they do not keep a steady water pressure and always have a much smaller internal hose diameter that restricts the water flow. The best thing to do is to use a regular garden hose and for the best water pressure connect it to the homes water main hose bib which always has the largest piping of water into the home. A lot of home builders use a 1" water pipe to the home, a 3/4" hose bib connect and the water main and a 1/2" connection for the backyard hose bibs....