SAIT PLUMBING SUPPLEMENTAL CODE APPENDIX WET VENTING 2.5.2.1.

Summary

This video explains the concept of wet venting in plumbing systems. It covers how water flowing through a vertical pipe creates a natural flow of air down the middle, forming the wet vent. The process involves sizing the wet vent based on fixture units and specific rules like limiting the number of toilets that can be wet vented. The video also highlights the importance of using symmetrical fittings and maintaining consistent pipe size to ensure proper flow. The tutorial emphasizes key guidelines, such as the maximum trap size and the correct method for determining the vent's size.

Takeaways

• 😀 Wet venting occurs when water flows down a vertical section of pipe, causing air to move down the middle of the pipe, creating a natural vent.
• 😀 The wet vent's length can be unlimited as long as it has enough grade and proper cleanout installation.
• 😀 A wet vent must adhere to specific rules, such as not being able to wet vent more than two toilets at a time.
• 😀 Toilets tied into a wet vent must be installed downstream, with symmetrical fittings like a Double Y used for the connection.
• 😀 The maximum size for a P-trap in a wet vent system is 2 inches to prevent pressure differences that could affect trap arms.
• 😀 Wet vents are sized 'full size,' meaning the pipe size remains consistent from the horizontal section to the vertical section under the fixtures.
• 😀 When calculating the size of a wet vent, only the fixture units that affect the wet vent need to be counted (excluding toilets downstream).
• 😀 In the case of two toilets tied into the wet vent, the symmetrical fitting ensures that the hydraulic load is managed properly.
• 😀 Fixture units from showers and lavatories contribute to the wet vent load, while toilets are not considered as part of this calculation.
• 😀 For a wet vent serving toilets, the size is determined by using the correct column from table 25-21, ensuring it is sized based on the appropriate fixture load.

Q & A

What is the basic concept of a wet vent?

A wet vent works by allowing water to swirl down a vertical pipe, creating a natural airflow in the middle of the pipe. This airflow is maintained as long as the pipe is sized adequately, resulting in a wet vent.

How does the water flow through the wet vent pipe?

As water is drawn down the vertical section of the pipe, it naturally swirls and adheres to the pipe’s interior. This creates a center hole for air to flow, allowing for a consistent airflow within the pipe.

What factors influence the size of the wet vent pipe?

The wet vent pipe should be sized based on the total fixture units and the sizes of the trap arms of each fixture. The pipe must also be large enough to allow for sufficient airflow, and it can be of unlimited length if the grade and cleanup are adequate.

Can a wet vent be of any length?

Yes, a wet vent can be of any length, as long as it has the proper grade and enough cleanup installed to maintain adequate airflow.

What is a critical rule when wet venting toilets?

You cannot wet vent more than two toilets at a time. These toilets must be symmetrically tied in and installed downstream of the wet vent.

How do toilets relate to the wet vent in the given example?

In the provided example, the two toilets are not directly in the wet vent but are wet vented through the two showers and two lavs downstream of the wet vent.

What fitting is used when installing two toilets downstream of a wet vent?

A symmetrical Double Y fitting is used when installing two toilets downstream of a wet vent. This fitting helps manage the large hydraulic load from the toilets.

What is the maximum size for a P-trap installed in a wet vent pipe?

The maximum size for a P-trap in a wet vent pipe is 2 inches. Larger traps should not be intermingled with smaller trap arms, as they may interfere with the flow.

What does 'sized full size through' mean in the context of wet venting?

Sized full size through means that once you determine the pipe size for the wet vent, it must remain the same size throughout the entire pipe, from the horizontal section up to the vertical part under the trap arms of the lavatories.

How do you calculate the size of the wet vent pipe?

To size the wet vent pipe, you count the fixture unit load that is affecting or dumping into the wet vent. The fixtures contributing to this load are the lavatories and showers in the example. Toilets are not counted since they are downstream of the wet vent.