I would suggest using a virtual outlet for the overflow switch. It's more intuitive and if you setup an email alert for it, you will get a notification that looks like this: Outlet Skim_Overlow = ON
If you don't use a virtual outlet and setup an email alarm, you would end up getting a notification like this which isn't intuitive at all. Especially if you make use of multiple float swithces. The notification would look like: Sw1 = Closed
This is how mine is setup. This assumes you are using a normally closed switch.
My virtual outlet is named: SkimOverflow.
SkimOverflow
If Sw6 OPEN Then OFF
If Sw6 CLOSED Then ON
Skimmer pump outlet:
Fallback ON
Set ON
If Outlet Return = OFF Then OFF
If Outlet SumpTooFull = ON Then OFF
If Outlet SkimOverflow = ON Then OFF
Note that I have additional level switches in my sump for SumpTooFull (also a virtual outlet). I make use of lots virtual outlets as you can see below in my email alarm outlet. Things like SalinityHigh, SalinityLow, Leak_Sump etc are all virtual outlets. Virtual outlets make those notifications much more intuitive. BoB_Unplug is also a virtual outlet. I have Sw6 in my custom breakout box constantly closed. If it's ever open, that means there is an issue with my BreakOut Box and it's likely unplugged. I have a 3 minute defer before the email notification is sent. I do that just in case I bump a switch or if a probe gets an errant reading. This insures that the change of state is constant indicating a true issue.
Email Alarm outlet:
Set OFF
If Temp > 82.7 Then ON
If Temp < 74.5 Then ON
If Outlet SalinityLow = ON Then ON
If Outlet SalinityHigh = ON Then ON
If Outlet SumpTooFull = ON Then ON
If Outlet SumpLow = ON Then ON
If Outlet SkimOverflow = ON Then ON
If Outlet Return = OFF Then OFF
If Outlet SkimOverflow = ON Then ON
If Outlet Leak_Sump = ON Then ON
If Outlet Leak_Pumps = ON Then ON
If Outlet Leak_Closet = ON Then ON
If Outlet Leak_Shed = ON Then ON
If Outlet BoB_Unplug = ON Then ON
Defer 003:00 Then ON