The code names specific devices and arrangements that qualify as trap seal protection for a trap subject to evaporation. Under the IPC, which of these is an acceptable method?
- A trap seal primer valve supplied from the potable water system and complying with ASSE 1018
- BA spring-loaded check valve installed in the trap outlet to hold the seal in place.
A check valve in the trap outlet is a moving part relied on to maintain a seal, which the prohibited traps rules bar. It also does nothing about evaporation, since that loss goes upward into the room.
- CA deep-seal trap used by itself, since a taller column takes longer to evaporate away.
A deeper seal only buys time; it does not replace the water that leaves. In a heated space an unused deep seal still goes dry, and the code does not list it as a protection method.
- DA cleanout plug left loose so that make-up air can enter and relieve the pressure swing in the line.
Loosening a plug opens a path between the drainage system and the room, which is the exact condition a trap exists to prevent. Nothing in the code contemplates breaking a cleanout seal on purpose.
Why A is correct
A trap seal primer valve fed from the potable water system and listed to ASSE 1018 is one of the named methods. It admits a small measured amount of water to the trap on a schedule or when supply pressure changes, replacing what evaporates. The standard reference matters, since the code accepts the device by standard rather than by description.
What this question is testing
Whether the candidate knows that trap seal protection is a defined list tied to product standards rather than an open engineering judgment, and whether they can recognize the standard designations that identify each acceptable device.
On the job
Emergency floor drains in electrical rooms, elevator machine rooms and mechanical spaces are the everyday application, and the choice among the listed methods usually comes down to whether a water supply is available nearby. Where it is not, a barrier type device listed to ASSE 1072 drops straight into the drain body and needs nothing else. Knowing the standard numbers lets you specify a device the inspector will accept on sight.
Memory technique
Prime it, barrier it, or feed it from a nearby fixture.
Exam tip
This section is a short list with standard numbers attached. Learning the numbers is faster than learning the descriptions.
Where to look it up
Chapter 10, the trap seal protection subsection listing the acceptable methods and their referenced standards. UPC differs on this point — follow the code your state has adopted.