A common wort chilling practice is to use tap water to perform the majority of the temperature change and to then use ice water to chill to the desired pitching temperature. I use tap water to take it down to about 80F and then ice water the rest of the way. To make switching the water supplies easier I made a simple manifold:
The left side accepts the garden hose while ice water is pumped into the right side. The middle connection goes to my immersion chiller. I used a garden hose quick disconnect on the left in order to be able to use the hose for rinsing tasks before chilling and to just make the thing easier to take apart. The ball valve on the right keeps the hose water from going through the pump and into my ice water. Connections to the chiller and pump are done with lengths of 3/8″ ID hose and female quick disconnects.
All the manifold parts are 3/8″ pipe while a 3/8″->1/2″ bushing adapts to the garden hose->1/2″ FPT fitting. The quick disconnect parts are: