Also known as Trap Seal Primer, these plumbing valves are used to add water to traps. In many cities, building codes require the installation of Trap Primers to prevent sewer gases from escaping a dry water drain. The most common application is in basements, where the floor drain is only used when it floods. This can lead to the drain drying, thus allowing sewer gases to enter the building. Not only is this a health hazard, but it can also lead to an explosion if there's a nearby ignition source. Canarsee offers the best electronic Trap Primer on the market, made by Sioux Chief.