How to Install MIFAB Trap Primer


The basic function of trap seal primers is to furnish the "P" trap, or deep seal of the floor drain, with water. Getting water into this water-deprived drain component eliminates the potential for the formation of methane gas. The gas is formed during the water evaporation process. It is highly explosive and can enter the work area from the floor drain, creating a potentially deadly work environment. These trap seal primers are hooked into the cold water side of the plumbing. They react to water flow and release water to the primer connector. Selecting and installing trap seal primers is obviously serious business.

Things You'll Need

  • MIFAB trap primer(s)
  • MIFAB install instructions
  • Local/national plumbing codes
  • Carpenter's rule
  • Marker
  • Open-end wrench
  • Pipe wrenches
  • Pipe sealant
  • Locate the trap seal primers where they will function most efficiently. Install all continuous flow and pressure drop-activated trap seal primers about 12 inches above the floor drain traps for every 20 feet length in the drain. Doing this will give the discharged water enough vertical drop to flow to the traps without pooling.

  • Pre-prime the traps and connect the pressure drop-activated primers to the water line with a vertical elbow. This will prevent debris from contaminating the primer's valves. Install the primer vertically. Specify easily accessible access doors for every trap seal primer. Make sure that these access doors are large enough to have hand access for more convenient lint and debris removal as these trap seal primers do have moving parts and will get dirty.

  • Install the line shut-off valve and union connections just in front of the trap seal primer along the water supply line for quicker access and repair. Doing this will preclude having to shut off water to the entire building to service the primers. Flush the water supply lines to remove all sediment and debris before installing the trap seal primers to keep them from getting clogged immediately and hampering performance. Do not use pipe dope or other paste since it can eventually work itself into the lines.

  • Mount the trap seal primer as near to the pressure drop source as possible. Install the trap seal primers onto the line and the flats on top of the primer with an 1 1/8-inch, open-end wrench.

  • Remove all loose flux and debris from the supply line to primer connection. Be sure to use Teflon tape on all of the joints. Do not use solder on either the inlet or outlet of the primer because the primer cartridge is polyethylene.

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  • Photo Credit plumbing fittings image by Greg Pickens from plumber, plumbing image by Greg Pickens from water meter replacement,plumber image by Greg Pickens from
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