Step 1: Cleaning
Firstly, partially disassemble the keg by removing the lid and gas post. Use a box wrench to loosen the gas post. Remove the o-rings with the o-ring tool. Unscrew the pressure relief valve (PRV) and remove the large o-ring on the lid. Take a moment to inspect the o-rings for any tears. If there are any, it is time to replace them with a keg rebuild kit. You don’t want to have a CO2 leak or allow any contaminants in.
Place all the kegs you intend to clean on one side; you’ll place them on the other side after cleaning. This makes it easier to keep track of your progress.
The cleaner we’ll use is Five Star PBW. It’s inexpensive, safe, and does a good job. The Mark II Keg Washer holds a gallon of water in the reservoir. Five Star instructions say to mix ¾ oz of PBW with one gallon of water. Three-quarters ounce is just about 1/8 cup, so get a set of measuring cups and a jewelry scale and you’ll be set. Get the full set of measuring devices as you’ll use the spoons for measuring out your brewing salts. Fill the reservoir with hot water and ¾ ounce PBW. Place the dissembled parts in the reservoir. You should be able to fit five or six kegs worth of components in the reservoir. Connect the disconnect to the beer post and place the keg on the washer. Because of the number of kegs I generally clean at any given time, I use a power switch to turn the washer on and off rather than unplugging it each time. Turn the washer on and let it run for 15-20 minutes. Pull the keg off and put a spare ball lock disconnect on the beer post to drain out the remaining cleaner. Turn it upside down again to empty as much out of the keg as you can. I then place the keg on the other side upside down so I know it has been cleaned – this is especially important when you are doing multiple kegs as you’ll likely be doing other things during each cycle.