Your wort should be cool before you pour it into the fermenter. If it is not, refer to Chapter 7 - Boiling and Cooling, for suggested cooling methods. But before you transfer the wort to the fermenter, you may have been wondering what to do about all the hops and gunk in the bottom of the pot.
There will be a considerable amount of hot break, cold break and hops in the bottom of the boiling pot after cooling. It is a good idea to remove the hot break (or the break in general) from the wort before fermenting. The hot break consists of various proteins and fatty acids which can cause off-flavors, although a moderate amount of hot break can go unnoticed in most beers. The cold break is not considered to be much of a problem, in fact a small amount of cold break in the fermenter is good because it can provide the yeast with needed nutrients. The hops do not matter at all except that they take up room.
In general however, removal of most of the break, either by careful pouring from the pot or by racking to another fermenter, is necessary to achieve the cleanest tasting beer. If you are trying to make a very pale beer such as Pilsener style lager, the removal of most of the hot and cold break can make a significant difference.
The most common method for separating the wort from the break is to carefully decant the wort off of it into the fermenter, leaving the break behind. Pouring the wort through a stainless steel strainer can also help with this approach. If you are siphoning the cooled wort from the pot, then a copper scrubby pad and whirlpooling can help. Whirlpooling is a means of gathering most of the break and hops into the center of the pot to better enable the siphon to draw off clear wort from the side. Rapidly stir the wort in a circular manner. Continue stirring until all the liquid is moving and a whirlpool forms. Stop stirring and let the whirlpool slow down and settle for 10 minutes or so. The whirlpooling action will form a pile in the center of the pot, leaving the edge relatively clear. The siphon won't clog as quickly now if it draws from the side of the pot.
If you have a vessel to use as a secondary fermenter, you can do either of two things.
You can siphon the wort into the first vessel, let it sit for a few hours to let it settle and then rack to your main fermenter to separate it from the trub.
Or you can pitch your yeast and let it ferment for several days as it undergoes its initial primary attenuation phase. The yeast are much busier eating the more available sugar at this point than scavenging trub, so you can wait until the bubbling of the fermenter slows way down and then rack to a secondary fermenter. Off flavors associated with sitting on the trub typically take a couple weeks to develop. Although removal of the trub from the fermentation is not critical, it is a factor to keep in mind in your quest for the perfect batch.
But let's get back to the job at hand, pouring the wort into the fermenter.
1. Pour the reserved 2.5 gallons of water into the sanitized fermenter. If you are using bottled water, you probably don't need to boil it first, but better safe than sorry. Aeration of the water in the fermenter prior to adding the cooled wort is a good way to ensure that there is enough dissolved oxygen for the yeast. It is much easier to aerate this smaller volume of water first, rather than the entire volume later.
2. Pour the cooled wort into the fermenter, allowing vigorous churning and splashing. This provides the dissolved oxygen (aeration) that the yeast need. Try to prevent the majority of the hot and cold break from getting into the fermenter. The whole hops help provide a filter. If some hops and break make it into the fermenter, it is not a big deal.
The concept of shaking smaller volumes can be applied to wort itself. Fill a sanitized gallon milk jug half full of wort and shake it before adding it to the fermenter. Do this for the entire wort and you will ensure you have adequate aeration.