Trap primer

Could someone please explain how a trap primer works. The first one I have seen was on a 1/2" line going to a floor drain in the basement. Has 35 - 75 psi marked on it, with a directional arrow. Does it allow water to continuously pass through to the floor drain, or is it controlled somehow? Thanks for the help.

A good number of trap primers sense the pressure drop in the system when a faucet or other device is opened, allowing small amounts of water to pass by the trap primer valve to the inlet side of the p-trap. Regards Bill

Trap primers were made due to plumbing traps drying up (water evaporating) when they aren’t being used, causing sewer odors to enter the area served by that trap. Floor drains are the most common traps that aren’t used on a regular basis.

Trap primers are devices that connect to a cold water line. It is installed in-line. Every time that cold water is used on that cold line, a small amount of water trickles down to the trap that is connected to the trap primer. The small trickle will keep the water seal from drying up.

Thanks for the help. That clears it up for me. Have a blessed Easter. Larry

read the other post i sent about veggi oil, it works here too. ( if no trap primer, i recommend it)