40 degrees F or C (which is 104 F)? Unless you live somewhere like Death Valley, I assume that is 40 F. If so, I do not see the need for a CLT at all.
Agree with this. If your ground water is in the 40F range year wound, you won't need to do anything to get the wort chilled. We'll maybe go to a plate chiller instead of the CFC (coil) chiller due to efficiency.
I chilled 13.5-14 gallons of hot wort (about 200F post whirlpool) to ~65F via my DD plate chiller (12" wide, 40 plate) in less than 10 minutes (was in the 8-9 minute range) in a recent batch. That's with the chill water going through about 100 feet of garden hose, outside (wasn't too hot outside either). I'm now taking the chill water feed from inside the furnace room, where it's even colder. Using a ball valve at the wort chiller outlet, to control the flow, got me to about 64F in a single pass, fast. Chill water was running full speed through the chiller.
From what I've been reading, CFC/coil chillers are not nearly as fast/efficient as plate chillers. At least not in the correct size range. My plate chiller takes up very little space, so a CFC consuming the same amount of space would be a joke.
To be clear, my summer water temps (I'm on a well) are in the low to mid 50F range. Winter temps are in the mid to low 40F range. Either way, I get to chill my hot wort fast with my setup. Plus, it's crazy easy to use.
Do note, that if you're whirlpooling and do go with a plate chiller DO get a wort strainer/filter to go in front of the plate chiller. I've used mine on the last two batches (since getting it) and have had zero issues with hop matter plugging the chiller. before this, I was using a hop spider to keep my chiller from plugging up. Much happier with the strainer/filter (from Brewers Hardware).