Do not assume this. My IFCS was designed to be the only return to the pool. Although one of the zones is 4 standard wall returns. I assume that this was to assist with the skimming action.
I replumbed mine to be able to isolate that zone of wall returns using a 3 way valve, with a check valve to prevent backflow through the zone valves, so that I could turn it on/off as I wished. And also so that if there were ever any issues with the zone valves, I could run my pool using the wall returns.
Knowing what I know now, I would only install an IFCS with a bypass to wall returns. I didn't know anything about pools and plumbing them when I started my build, so I didn't think about any of that. Fortunately I was able to modify my system to do that.
I don't know all of the IFCS system manufacturers, but I'm pretty sure Paramount and A&A both design wall returns as part of their system.
@Rattus Suffocatus installed an IFCS in his pool and I am pretty sure his builder plumbed a bypass around the IFCS.
I would hesitate to use a builder, or at least have him install the IFCS, if he is refusing to put in standard returns.
Looks like HermanTX just stated all of my points also. I was busy typing and not paying attention and then got sidetracked and never posted it.
--Jeff
Yes, I can turn on the standard returns-- I have Jandy valves so I even think I can run both at once. It's really the only way I can aerate the water to bring up pH when I am fighting TA-- though this year I bought a secondary cheap pump to play with to do that and do a little "ghetto" solar heat experiment.
You definitely want to be able to switch to standard returns, the extra plumbing is minimal honestly. If you are doing a Venturi skimmer you also want the valve and plumbing to switch over to suction installed as well. My pool is on the cheap end of features (no heat) but those came standard and yes I have used both.
As for the liking the Paramount IFCS? I'm still doing the agree to disagree thing. My dogs like to knock the xeroscaping rocks into the pool (and the youngest one has a taste for the solar covers...

) -- I think If I relied on a robot those rocks would have destroyed the robot by now. They tend to not get sucked into the main drain with the floor system either.. they end up in "clumps" or groups that I need to vacuum out, but even that little $20 garden hose Venturi vacuum from Wally World does an adequate job of that. That little bit of work I can live with.
Again, if I weren't in the Arizona high desert with just gravel and desert plants for landscaping I suspect I wouldn't like the system as much. But it works great here. I suspect if I had grass and actual living plants that it would clog on that material.
The other thing I like about it, is that when it starts to slow down, the filters need to be cleaned. This works on volume, of course, and that starts going down before the pressure differential starts showing.. and what do I mean by that? I put on the second pressure gauge on the Paramount head... you know it's getting time when you see more than a PSI or two difference in between the pressure gauges. Then if it occasionally starts skipping a zone (hangs on the last one) you know right then and there it's time to clean the filters out.
As for a SWCG? Do you like to wash dishes by hand, or do you prefer the convenience of a dishwasher? And in this case the long term price differential isn't even as much as that example. I had no less than three family disasters happen right after Christmas at the same time. I still haven't resolved any of them, but I am pretty close now on one.
I have been neglecting my pool honestly, but the SWCG has keep my pool looking really good (yeah it needs a really good brushing before we swim). I honestly don't know if I would have kept the pool looking that good this year because of lack of time without. I am sold that it is the best way to maintain a pool, especially if you are following TFP. It's an expensive toy, but I am glad I just sucked it up and got one.
The worst thing I am guilty of because of the SWCG running is letting TA and pH get too high a couple of times... one time I didn't test for a month...
I don't recommend this at all.. but .. no issues at all with that abuse. Yes I would check on the unit every other day.. make sure it wasn't reading "lo" temp, etc.. if so I'd reset and it would then come on.... but I was terrible on doing proper TFP testing....