I'm going to jump into this one looking first at fermentation temperatures and then at water. Yes, you can get a bug in your beer, but as was mentioned earlier, I think a lot of beer problems are blamed on infections because an infection is an easy scape-goat. Yes infections do happen. But keep in mind that people have been making really good beer for centuries, long before the invention of modern sanitizers. Reasonable sanitation practices reduce the possibility of infections to almost nil. One-Step will clean your equipment satisfactorily if you are in the practice of cleaning as soon as you are done brewing. Let it set a few days before you clean up and all bets are off. And +1 to the use of StarSan to sanitize
everything before it contacts your beer.
As others have said, most ale yeasts do their best work when the fermenting beer is held at 66-68F. That is
the temperature of the beer, not the air temperature in the room. Fermentation is an exothermic process. That means it generates heat. If the room temperature is 65F the actual temperature of the fermenting beer may be as high as 70-72F. With many yeast strains this is enough to produce off-flavors in the beer. (Trust me on this one, I've dumped a few batches over the same problem.)
Advice? Get a dedicated fermentation refrigerator or freezer. Set it up with and STC-1000 temperature controller. Put the sensor in a thermowell so it is measuring the temperature of the fermenting beer, not the temperature of the fermentation chamber. If this isn't in the budget, put your fermenter in a space that is at least 5F cooler than your target temperature for fermentation. It only needs to stay this cool for the first 3-5 days of fermentation. After this initial period most of the danger of off-flavors has passed. And with the drop in fermentation activity the beer will be much closer to actual room temperature.
The next issue to look at is your water. Many people are given really bad advice in thinking if the water is OK to drink its OK to make beer with. There can be things in your local water that will absolutely destroy the flavor of your beer. If your municipal water utility gets their water from different sources as the seasons change this can lead to seasonal problems with the beer you are making. (Personal and painful experience speaking on this one too!)
Advice?
Step 1: Pull a sample of your brewing water and send it to Ward Labs in Kearney, NB. For ~$30 they'll do a complete analysis and email you the results.
Step2: Contact your local water utility and ask to speak to one of their water engineers. Tell him you're a home brewer and ask if the sources for municipal water vary seasonally. Is there any chance there might be chloromines in your water. He'll probably be surprised to hear from you but, if he's like ours, will be very happy to help. Heck, they might even send you a water analysis for free. Keep in mind that Chlorine and Chlororomines can destroy your beer. Chlorine can be boiled off. Chloromines cannot, but they can be avoided with a change in water source or your water can be treated with Camden tablets. Other water issues might call for changing the source for your brewing water.
Good water + good fermentation temperature control = reliably good beer!
Cheers!
