 Most UDS builders/users would say a water pan defeats the true pit BBQ nature of the UDS, as the drippings from the smoked meat should land on the coals, burning up, and imparting a unique flavor one cannot get with a water pan.A vertical water smoker (also referred to as a bullet smoker because of its shape) is a variation of the upright drum smoker.It uses charcoal or wood to generate smoke and heat, and contains a water bowl between the fire and the cooking grates.