What Is a Trap Primer?
A trap primer is a plumbing device that sends water into a drain trap to keep its seal intact. The water blocks sewer gas from moving through an unused floor drain. Trap primers connect to a water supply and may activate when nearby plumbing runs or when water pressure changes.
Quick Facts About Trap Primer
Category
Drain protection device
Used for
Maintaining floor drain trap seals
Common confusion
Not a drain cleaning tool
Also called
Floor Drain Trap Primer, Trap Seal Primer
Often discussed with
Storm Drain Cleaning, Drain Cleaning
Key Takeaways About Trap Primer
- It serves floor drains that may sit unused.
- The device protects the trap’s water seal.
- It isn’t the same as a drain cleaner.
How Trap Primer Works
A trap primer sends water into a floor drain trap when the connected plumbing system creates the right demand. The added water keeps the trap seal present. A sealed trap blocks sewer gas from entering the building through the drain opening.
Related glossary terms: P-Trap, Sewer Cleanout.
Some primers connect to a nearby cold-water line. Others use a pressure change from a fixture, such as a toilet or sink. The primer sends a small flow through a tube that ends above or inside the drain trap. The setup must keep the tube secure and clear.
During Storm Drain Cleaning, a primer may appear near a floor drain, mechanical room, or utility space. Cleaning the drain does not repair a primer that fails to add water.
Expert Note
When we inspect a drain during Storm Drain Cleaning, we check nearby primer tubing and connections. We look for blocked outlets, loose fittings, and signs that the trap has dried out. We also separate primer problems from clogs in the drain itself.
Trap Primer in Practice: A Real-World Example
A commercial building has a floor drain near equipment that rarely releases water. During Storm Drain Cleaning, a plumber checks the trap primer connection and clears the drain separately so each part can work as intended.
Related Services
Related Terms
P-Trap
A P-Trap is a curved plumbing fitting beneath a sink, shower, tub, or other fixture drain…
Sewer Cleanout
A Sewer Cleanout is an access point on a building’s drain line that lets a plumber…
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