^^^ This on the temp spikes if the water pan dries up.
Here is some helpful info.
Water pans. Water pans are not for making gravy.
1) Water in the pan absorbs heat and never rises above 212°F. This helps you keep the temp down to 225°F, a temp I recommend you learn to hit with regularity.
2) Water helps stabilize the temp in the cooker and minimize fluctuations because water temp takes longer to rise and fall than air.
3) A water pan can block direct flame when you need to cook with indirect heat.
4) Water vapor mixes with combustion gasses to improve the flavor.
5) Water vapor condenses on the meat and makes it "sticky" allowing more smoke to adhere.
6) The pan can add humidity to the atmosphere in the cooker to help keep the oven from drying out your food. This can vary significantly depending on the design of the cooker. If you place a water pan a few inches below the meat in a pellet cooker, the water does not get very hot, and it will have little effect. In an offset or bullet smoker, with the water pan directly above the coals, it can make a significant difference in how much water evaporates from within the meat and how moist the meat will be.
7) The humidity keeps the meat moister and that slows cooking as the moist surface evaporates and cools the meat. This allows more time for connective tissues and fats to melt.
Try to use only hot water. Cold water will cool your oven down a lot and should only be used if you are running hot and need to cool it down. And fill the pan to just below the lid so you don't have to keep opening the lid to refill. Put it above the hottest place in your cooker so more water will evaporate.
[h2]What goes in the water pan?[/h2]
Pitmasters argue over what should go in the water pan. Some say sand should go in the pan, some say beer, wine, apple juice, onions, spices and herbs, you name it. What works best?
There's a reason it is called a water pan.
Some folks like to put sand, dirt, gravel, or terra cotta in the water pan. They do nothing for the humidity, or for the flavor. They may help stabilize fluctuations, but will not keep the temp down like water. Water will not go over 212°F. Sand and other solids will heat up to whatever the oven temp is. So if you have a charcoal bullet smoker or a gas smoker that tends to run hot, say 250°F, but you want to be at 225°F, then water will help you keep it down. Eventually the sand will warm to 250°F.