I would have preferred a #1 or #2 rather than the #3 Injector - Yellow

Even though I thought I had a grasp on this, I went down a rabbit hole thinking about your injector recommendations and dug into the 5810 SXT Installer Manual. For my 13"x54" / 2.5 cuft tank the 4.1.1 Injector/DLFC/BLFC-Valve configuration table indicates the #3 Yellow injector is correct, but my 0.25 gpm BLFC is undersized and should be 0.50 gpm.

Q1: If BLFC only controls refilling of the brine tank at the end of the cycle, then it would appear the only advantage to the 0.50 gpm over the 0.25 gpm BLFC is that it would cut the refill time in half. Is it that simple or am I missing something?

Moving on to the injector sizing...

The injector sizing formula in the manual indicates the total flow rate of the injector should be about 4x the resin volume per hour.

That means my 2.5 cuft of resin requires a total injector flow rate of 1.25 gpm. The #1 White injector has a total flow rate of ~1.1 gpm @ 65 psi and the #2 Blue injector has a total flow rate of ~1.6 gpm @ 65 psi. My current #3 Yellow injector has a total flow rate of ~1.9 gpm @ 65 psi. The #1 White or #2 Blue injectors are certainly closer to the 1.25 gpm target flow rate which corroborates your stated preferences for injector selection.

The #1 White injector will draw brine at ~0.32 gpm, so it will pull my target of 6 gal through in ~19 min.

The #2 Blue injector will draw brine at ~0.53 gpm, so it will pull my target of 6 gal through in ~11 min.

My current #3 Yellow injector will draw brine at ~0.60 gpm, so it will pull my target of 6 gal through in ~10 min.

Q2: Based on these times, I'm confused as to why the BD time is 60 minutes. Is that just so the brine has enough contact time with the resin for the ion exchange to occur?

Q3: The table recommends the #3 Yellow injector for a reason, so I'm curious what that reason is since the #2 Blue injector and #3 Yellow injector draw brine at nearly the same rate. Is the #3 Yellow injector specified because its higher total flow rate allows the brine to be more evenly distributed through the resin over the larger cross sectional area of a 13" tank?

Q4: A counter argument against the #3 Yellow injector and for the #2 Blue injector is that maybe the lower total flow rate of the #2 Blue injector would force less rinse water through the resin allowing the brine longer contact time?[/QUOTE]