A water smoker allows you to smoke meat at temperatures well below 300°F for many hours. The Weber version is basically an upright bullet-shaped unit with three sections. The charcoal burns in the bottom section. For smoky barbecue aromas, add a few fist-sized chunks of hardwood to the coals right from the beginning. The meat will absorb the smoke best when it is uncooked.
The water sits in a pan in the middle section, preventing any fat from dripping onto the coals and, more importantly, keeping the temperature nice and low. The meat sits on one or two racks in the top section.
A water smoker has vents on both the bottom and top sections. Generally, it’s a good idea to leave the top vent wide open so that smoke can escape. Use the bottom vents as your primary way of regulating the temperature. The less air you allow into the smoker, the lower the temperature will go.
Generally speaking, if the ring in the bottom section of the smoker is filled with lit charcoal, and the water pan is nearly filled, the temperature will stay in the range of 225° to 250°F for 4 to 6 hours. This is an ideal range for barbecuing food like pork ribs, turkeys, and standing rib roasts.
When you see that very little smoke is coming out of the top vent, add another chunk or two through the door on the side. Wood chunks burn slowly and evenly, so they are a better choice than wood chips in this situation. For cooking sessions longer than 6 hours, you will probably need to add more charcoal occasionally. The timing will depend on your type of charcoal and how fast it burns. If you are using charcoal made with unnatural fillers, you may want to light the briquettes in a chimney starter first; some people can taste off flavors in food cooked over unlit briquettes.
During long cooking times, also be sure to replenish the water pan every few hours with warm water. But keep the lid on the smoker as much as possible. That’s critical for maintaining even heat.