6) In order to prevent infection of the wort and to cause an effect known as the "Cold Break", during which all the material that has clumped together during the "Hot Break" falls out of suspension, it is essential that it is cooled as quickly as possible. I use a simple immersion chiller that is added to the boiler at the same time as the Irish Moss. This acts as a simple heat exchanger and is normally connected directly to a cold water tap, but, as I don't have conveniently accessible running water in my unit, I use a 60ltr bucket filled with cold water as my cooling reservoir and feed the cooler via gravity. Alternatively, you can leave it to cool overnight if it is covered, but this may affect the later clarity.
When the boil has finished, the first 10ltrs of cooling water that come through the chiller are around 70°C. If you collect this in one bucket, then collect the next 20-25ltrs (which will average out at about 40°C) in a separate bucket, and finally collect the last 10-15ltrs in the first bucket, the temperature of all this cooling water will average out at about 40°C and you will have plenty of warm water to use for washing all your equipment.
I adjust the flow rate of the cooling water to around 1½-2ltrs per minute, so it normally takes around 30-40 minutes to cool my wort to 20-25°, depending on the feed water temperature. This can vary from 17-20°C if I'm brewing in the summer to as low as 10°C in winter. The lower the feed water temperature, the faster the wort will be cooled. When the correct temperature has been reached (20-24°C), the hops and proteins thrown out of suspension during the "hot" and "cold" break points will have settled on the bottom of the boiler. This is known as the "Trub".