Hot Topics: Vented Cat Privy

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It’s not just a question of the best way to drill through cinder block, but why. In this case it’s to provide a little air to the private, under stair, cat privy going into a finished basement. With a respectable portion of the forum having already performed this project, they weigh in to help a fellow member get it done. In the end, your cats may even thank you, even though they know they deserve it.

Original Post: New Exhaust Duct, Need to Drill Through Brick

horford Member

Please don't poke fun of me too bad, but I’m finishing my basement and am designing a “cat litter-box room.” It's going to be under the stairs. I want to install a motion sensor attached to a fan that will exhaust the smell through duct and outside of the house.

I don't see any other way other than drilling through the cinder block. What is the smallest diameter hole I can get away with? Smallest, strongest duct? It's going to run about 10 feet or so. What are some best practices to doing this? I'm guessing it shouldn't be a block that is supporting a beam.

Thanks for any advice.

Highlights from the Thread

Gunguy45 Super Moderator

I'll never poke fun for that project... I've done similar. 3-inch would probably be the smallest duct you'll find. How did you plan on drilling and what kind of fan?

Nashkat1 Forum Topic Moderator

Use a masonry bit long enough to go all the way through the block. Drill a pattern of holes about ½-inch larger than your duct. Use a hammer and/or a masonry chisel to open up the hole on each side.

I hope your cats will tolerate having their litter box in a room where a fan starts up every time they walk into it!

Gunguy45 Super Moderator

They'll learn... mine did. Fan and light came on when they went through the door. Have to acclimate them to it.

horford Member

He he. I’m glad I’m not the only one who's done this... and I’ll admit I got the idea from surfing around the web. I originally planned on hooking up a computer fan to solar panel. Now, I just want a solid (hopefully quiet) fan that will switch on for about 30 minutes or so after it's triggered.

I will begin to look around for 3-inch duct and a fan I can attach to it.

Any suggestions as far as finishing the hole in the cinder block? Do they make plastic exit vents (similar to a dryer vent) that small?

Do I want to aim the hole in the center of the block? Or towards the top/bottom, or does it not matter?

Thanks again.

ray2047 Group Moderator

I suggest using a bathroom exhaust fan that vents through the wall.

Example: Broan 70 CFM Through-the-Wall Exhaust Fan Ventilator-512M at The Home Depot

PJmax Forum Topic Moderator

They make 3-inch thru wall vent kits with an interior trim ring. 3-inch diameter Venting Exhaust Hoods & Kits - Deflecto

You would want to keep the hole centered top to bottom in the block and in one of the hollows. In the pic below you'll see what I mean about hollow spot.cinder block

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