It has not been my experience that they are necessary: The atmospheric condensation forms on the valve as an ice ball, not as liquid condensate that drips off. The potential for dripping would be when you are taking the system down and everything warms up to ambient. As the ice ball melts, it would have to drip. Floor drains seem to take care of that eventuality, if the valve is indoors. Outdoors: it drips on the ground and soaks in to the soil or evaporates from the pavement.