Homemade PVC drain -- needs aav?

[highrocklaker]

We have a masonry boathouse that has a flat cement roof. Water will often pool on top of this roof. There is a drain on top of this roof, covered with a flat metal screen, and it drains into some 1.5" PVC pipe that runs vertically through the masonry, then across the ceiling on the interior and then back down and out the base of the masonry. The piping was clogged with debris and I've replaced the PVC and it is now clean and free of obstructions. However, during heavy rains, the water will cover the top of the drain and then no water will exit the drain. I'm assuming that I need to modify the piping to ensure air can enter the drain -- is that correct? If so, what's the best way to introduce air into the piping? Must air be introduced at the top of the drain run or can I install an aerating valve anywhere in the piping? Thanks in advance for your advice!

 

[Riickk]

As I learned it, AAV slows draining, they're used to prevent a suction developing that could empty the trap of a sink - for example.
Can't think of anything that would stop a pipe from draining once water was above the top of a drain opening, except something odd that would act as a valve / barrier when pipe is completely full.

 

[Jeff Handy]

It sounds more like the flat drain is just getting clogged.

You can install a drain opening with a raised cage to filter out debris.

 

[Jeff Handy]

Something like this.

https://www.slideshare.net/acorneng/jay-r-smith-mfg-co-fullbore-siphonic-roof-drains

You can also find strainer baskets that can clamp or screw onto existing flat drains.