Floor Drain: how to prevent outside air?

[Derek B]

Sorry if this is the wrong forum, I have no idea where this question fits...

I have a laundry room drain that is a 2" ABS pipe straight down then out to the outer wall of the house via our crawlspace. I had it blocked because we had the laundry in the garage, but now it'll be in the house and I want it unblocked. Except, there is air that easily flows up and into the house via that pipe. What's a good way to allow it to work as a water emergency pipe out of the house while not allowing air in? I'm about to get the washer/dryer combo installed, so my hope is I won't have to slide it back out, but can implement any solution either at the exit point or underneath in the crawlspace. But open to all ideas. thanks for your all's help!

 

[LLigetfa]

You need a trap and a trap primer but if the air infiltration is poorly managed placing the neutral pressure plane (NPP) too high, it cold overcome the pressure of a traditional trap. House envelope infiltration should be better managed by sealing up high and allowing makeup air down low to lower the NPP. Mismanaged NPP can cause reverse drafting of flues and CO poisioning.

 

[Sponsor]

 

[LLigetfa]

Oh, should I assume this is in California (LA) as per your profile? What is the total vertical drop from the floor drain to where the pipe exits? Maybe a simple swing gate check valve at the exit would suffice.

 

[Derek B]

Hi, thanks for your reply! I'm in the Los Angeles area yes. The drop is about 1 foot is all. From the raised floor down into the crawlspace, then out toward a crawlspace vent. The ducting for the dryer exhaust is on a different side of the house and so no risk of CO flowing back thru this drain.

Would this be an easy solution?

https://www.homedepot.com/p/2-in-Se...CBSgueONzdXAafMxLnAaAt8fEALw_wcB&gclsrc=aw.ds

I found a similar one at Lowes, but worry the valve flapper is too stiff for my very low pressure water should this drain ever be needed. They had a 1-1/4 variant that had a flapper that was much more flexible and would probably open easier, though I'd have to adapt the 2" ABS down to fit it.

Appreciate your advice and time!