Conserve water used in immersion chilling?

To go along with winwaeds answer flow is usually really over done by most.

I made my own immersion chiller, when I did I built in two temp probes. What I found is that I could reduce the flow to a trickle about 0.5 gallons per minute was optimal for my chiller, more flow didn't pull any more heat off.

So basically very little water really needs to be used. Especially if you can use ice water for the chill.

I have a 3 vessel system, with each HLT/MLT/BK at 20 gallons. I run the water fairly slowly, and collect in the HLT, either for use in cleaning or even a new brew. The water will keep fine for 24 hours when covered.

I start by saving the hottest water in my sink, to be used for cleaning the immersion chiller and other items post-brew. Once I have enough there, I save the water in buckets to be used for watering plants inside and out. Once the wort temperature drops to 120-130 F I switch over to a closed system. I have a small picnic cooler with a submersible pump in it, and I fill the cooler with ice water. The return water from the immersion chiller goes back into the cooler. I add more ice as needed, and if it gets too full I run some of the water off to a bucket. You could use a closed system from the start if you have a large enough reservoir of cold water and ice.

Slowing down the stream might help conserve some (the water stays in the pipe longer and heats up more); but often people find a use for the water instead.

One suggestion is to send your hose into a washing machine to pre-fill it.

I use it to top up the garden pond. Yes it is very warm at the beginning but dilutes easily (no boiled fish!) as the pond is 2ft deep; and in a very short time the water output is at a more fish-friendly temperature.