I live in Las Vegas where we deal with near 90 degree tap water in the heat of the summer. I have a plate chiller (Sherron) as well as an immersion chiller with a recirculation arm. See More Beer http://morebeer.com/view_product/9147/102204/Wort_Chiller_Recirculation_Arm_-_Option_Two
I brew 10 gal batches and used the plate chiller in the winter for the last few years with great results. But have found IMHO that the best way to get wort down to pitching temps in the summer is to chill in 2 stages. First I start with tap water through the immersion chiller and a march pump on the recirculation arm. After the wort gets down below 100 degrees (8 to 12 min) I switch out the tap water and reticulate Ice and water from an old 6 gal bucket using a $25.00 immersion water fountain pump. (apr. 10 pounds of ice for ales and 20 for lagers)
Yes it’s a pain, but I am transferring pitching temp wort in 20 to 30 min. when it’s 115 outside.