Once a year I like to take a day to go through all my homebrewing gear and make sure everything is clean and working right. It feels good to go into a deep-cleaning mode from time to time to make sure you're not picking up off flavors from your kettle or worse—infections from equipment that should have been discarded.
I start out simple: using my dye-free, fragrance free Oxyclean, I scrub out all my stainless steel kettles. Then I go through each piece of equipment I use throughout the brewing process, making sure it's clean and in working order.
Clear tubing is the first place where debris can build up over time. Every homebrewer has at least some tubing on their racking cane and for their bottling wand. People who have spigots on their brewing kettle or mash tun will also have tubing used to transfer liquid from one container to another. The bad part about these hoses is that they can be tough to clean. The good part about them is that they're inexpensive and easy to replace. Any hardware store like Lowes or Home Depot will have tubing near their plumbing department for around 50 cents a foot. The tubing that connects to your racking cane is 3/8" inner diameter (I.D.) size, and the larger tubing that you might have connected to your kettle spigot is 1/2" I.D.
"any defect you find is an easy hiding place for bacteria and stray yeast that will quickly infect your wort"
Inspecting your fermentation vessels is the most important maintenance checkup you can make. Check your fermentation buckets carefully to make sure there are no scrapes or scratches in the plastic. If you use glass carboys, hold them up to the light and rotate them slowly to check for interior damage caused by racking canes or cleaning brushes. If you take care with your equipment, there's usually no problem. However, any defect you find is an easy hiding place for bacteria and stray yeast that will quickly infect your wort. As hard as it will be, scratched fermentation vessels need to be retired to non-brewing purposes. It's just not worth throwing out a whole batch of homebrew because you didn't replace a $10 bucket or $30 carboy.
While fermentation vessels are the first piece of equipment to check for scratches, anything that touches the wort after the boil should also be inspected and replaced if scratched. That includes, but may not be limited to, spoons, racking canes, and funnels.
While I'm doing my annual equipment clean up, I also like to take the opportunity to check the calibration of my thermometer and hydrometer. Having an uncalibrated thermometer may not be a big issue if you're strictly an extract brewer, but anyone doing partial mash, brew-in-a-bag or all grain brewing needs to be more careful. It's not uncommon for thermometers to be several degrees off, and if you're mashing at 157° when you want to be at 152°, you might end up with a very different beer than what you intended.
The easiest way for homebrewers to calibrate their thermometers is by checking the freezing point and boiling points. To check the freezing point, take an insulated cup and pack it tightly with finely crushed ice. Fill the rest of the mug with water and place it in the refrigerator for a half hour. The goal is to get the ice just to the melting point, and not a bit higher, so that the water is exactly 32°F. Take the cup out of the fridge and add more crushed ice so that it's filled with ice all the way to the bottom of the glass. Let it rest for a couple minutes, then place your thermometer directly in the center of the glass, holding so that it's not touching the bottom. The thermometer should come to rest at 32°F exactly. If it doesn't, make a note of how far off it is. Fancy thermometers have an adjustment screw on the back of the dial that you can use to reset the temperature. If you don't have an adjustment screw, make a comment in your brewing notes that your thermometer reads 2° too high, or 4° too low, or whatever the case may be.
Checking the boiling point of a thermometer should just be a double check, since if the freezing point is off, then the boiling point should be off by the same amount. In reality, this isn't always the case, but for even modestly priced brewing thermometers it will be pretty close. The technique is exactly what you would expect. Get a pot of water deep enough to submerge the thermometer up to a rolling boil, and hold the thermometer in the water, keeping it a short distance from the bottom of the pot. The temperature should read 212°F, and if it's not then make adjustment accordingly.
Calibrating your hydrometer is important if you're worried about your brewing efficiency or making sure that your alcohol content calculation is correct. It's also very easy to do. The hydrometer is used to determine the Specific Gravity of wort, which changes based on the density of the sugar dissolved in the water. Since there is no sugar in pure water, we can use this to calibrate the hydrometer. Using distilled water works the best, since the reading won't be impacted by the natural mineral content that may be in your tap water. Measuring the Specific Gravity of the water at 62° F (using your calibrated thermometer) should produce a reading of exactly 1.000. If it's off by a bit, make a note of the difference and use that to adjust any readings you take.
Now your equipment is spruced up and ready to go for your next brewday! We've arrived at stout and porter season; these beers are a lot of fun to brew and usually turn out great for homebrewers.