Abstract: Disclosed is a primer for charging and replenishing conventional water traps, such traps being required by most building codes. The primer is a section of pipe inserted in the drainpipe of a water user station (e.g. sink or washing machine), and has a tap or bleed line that diverts a portion of all drain water to the water trap. The bleed line can have a screen across it to filter out solid particulates that might otherwise clog the trap, and the bleed line can also have a lip or spoon that extends toward the center of the main drainpipe to facilitate the diversion of water. Having no moving parts, the primer is especially reliable, and can be inexpensively manufactured. Using only drainwater, rather than feedwater from the cold tap, as is done conventionally, the primer conserves water.