One of the most common questions we get is “Why isn’t there a cap or elbow on the pipe outside? Won’t rain get in?” Everybody wonders the same thing, and it makes perfect sense! The answer though, is not so straight-forward. The MAIN reason we don’t put a cap or elbow on the pipe to prevent rainwater from entering your mitigation system is simple: the State of Ohio forbids it! But why would they forbid a simple cap? In general, anything that is added to the opening increases resistance to airflow and has a chance of clogging up (debris, rodents, ice, snow etc). To play it safe, the only thing the Department of Health allows us to place on the top of the pipe is a rodent screen (a 1/2″+ wire mesh – no smaller).
The second reason, which many people are surprised by, is that it really doesn’t matter! Over the course of a year in Ohio, it is estimated that 7 gallons of rainwater will enter the PVC standpipe that terminates above your roof. However, over 1400 gallons of condensation will be formed (and subsequently drain back down the pipe) in that same period of time! Over 200x more water will enter your radon mitigation system from condensation, than rain.
All of our fittings and equipment are rated for use in wet conditions. This includes (of course) the pipe, fan, electrical connectors, electrical box & electrical switch. The fans are designed in such a way to allow the water to pass through the fan blades and eventually back into the gravel/dirt beneath your basement floor. Condensation, on the other hand, is formed as a result of the moist air being pulled from below your slab reacting with much warmer (or cooler) air outside of the PVC pipe. Water droplets form inside the pipe and gravity takes care of the rest. Many do not think about the fact that there are thousands of gallons of water in the soil beneath and around your home…so we let the water drain right back where it came from!
In summary, we can’t cap your pipe because of Ohio law. However, the reason you think you’d want to cap the pipe isn’t a great reason, after all (because of condensation).
Radon Mitigation (Exterior)
Found this site through Google search. This is very helpful and exactly what I was looking for. Thanks!
Same here!
Thank you! I was so confused and worried for a bit. Great explanation:)
This is a great explanation. Thanks.
Thank you for a very informative answer. One less thing for me to worry about as a homeowner!
I learned. Thank you.
Will the rain water and condensation draining down to the suction hole in your basement wash away the dirt around the footings of the house and cause problems?
No, it will not
how about exhaust fan pipe from fume hood lab?are there still no need to put elbow/neck or cap?
We’re not sure. we don’t deal with fume hoods. Seems like you’d want a cap, though.
Thanks for the answer. I’ve wondered for a long time.
I’m in TN and not OH so the codes may be different, but I have a mitigation system at my house with a 4″ pipe that terminates exactly as pictured. Every time we get heavy rain I can hear water gurgling in the pipe where it runs into the garage floor.
These fans may be made to withstand water ingress, but I can’t imagine it is good for it to have to chug through all whatever standing water is in the pipe until it is eventually able to be absorbed into the ground.
I also don’t understand why some sort of 180 degree bend at the top so that the open end of it faces the ground wouldn’t be permissible.
In Ohio, it’s required to prevent the possibility of condensation dripping from the top of the horizontal pipe’s opening from freezing and completely blocking the pipe.
What about leaves and other debris from trees like small nuts, twigs etc.? Would this not create a clog? I’m not in Ohio but in Kansas, a little worried because of how much stuff falls off a large tree above my house.
This is code in Ohio…we don’t have a choice.
When they installed our system, the pope outside only goes half the way up the side of the house. I noticed this past winter that I was building up moisture freezing on the siding. Is that normal?
Ohio now requires termination above the roofline in most situations.
A bypass drain will alleviate any concerns on rain and condensate. I noticed you pic has the pipe terminating just above a window. In most states it must be a minimum of 10ft from an opening. Is it different in Ohio?
They don’t help with anything below the bypass, nor can they help with poor draining sub-slabs.
In OH, we must be 2 ft ABOVE or 10ft to the SIDE of a window.