The trap primer is used to maintain the level of water in the trap.
This trap is used to prevent accumulation of gases inside the plumbing system - usually U or S shaped pipe, by maintaining the constant level of liquid in the trap.
Good day, in Nyc Hospitals, I've installed flush type floor drains in operation rooms and in Emergency rooms. The purpose of this was to flush down blood,contaminants, and to prevent methane gas from passing through. Sewer gases can be lethal to someone's health and explosive. I hope this helps.
Regular trap primer should be installed on a main water pipe (in vertical position) in the bathroom, and should be connected by a ½” copper pipe (or PVC) to the floor drains P trap (few inch above the water level in P trap), to drip a few drops into the bathroom’s floor drain or any floor drain (or floor sink) which is located in the adjacent area to the bathroom. Every time that someone flushes the toilet or urinal, the water pressure in the main water line in the bathroom will drop and trap primer releases a few drops to the floor drain P trap, in order to always keep a water in the P trap to block the odor to traveling to the bathroom space.
In areas other than bathrooms which there are no toilets or urinals and therefore no flushing system apply, the regular trap primer cannot work as there is no pressure drop happening in the water system in that area. In these cases the electronic trap primer will be used to act like a regular trap primer. In electronic trap primer box, there is a solenoid valve which works with a timer that has been adjusted to energize the solenoid valve to open and allow a few drops of water drip into the floor drain (or floor sink) P trap to block the odor. To see the device visit http://www.pppinc.net/2/submittals/TPV_Prime_Time_Flush_150.pdf