Built In, Self Venting Cat Box





Introduction: Built In, Self Venting Cat Box

About: I frequently get the bug to build something. I don't like to do anything half-assed. I want to see how many functions I can cram into one project.

This is a self venting cat box I built. It does have a bathroom fan inline but, that turned out to be overkill. I tapped into the vent stack for the tub while I was remodeling the bathroom. Also did all the tile and everything else, really.
The box emits no smell, the hallway down one side traps loose liter before the cats jump out and keeps the dog from getting treats. It was a blast to make.

Step 1:

Looking in from the back of the shelves during construction.  There is a small closet that goes to the adjoining bedroom.  I sacrificed part of the closet for shelves in the bathroom and the cat box.

Here you can see the pipes leading from a small bathroom fan to A dedicated vent pipe.  That pipe goes up and through the roof.  I added power to charge a cordless razor or curlers (do people use those any more?)  The blue electrical box behind that pipe houses the timer switch. 


Step 2:

Here is the timer from the front.  At one point I was going to put a motion detector in the box.  Glad I didn't because there seems to be a natural draw in the box that self clears the air.  Not enough to pull heat out of the house.  Just a slow steady flow to removes stink.

Step 3:

The box is coated with shellack.  Shellack resists soaking in any odor and it's waterproof.  On the floor of the box I poured about 1/8" of epoxy in case of spills.  The finished box can hold water. 2 inches deep (just had to try for fun)

Step 4:

The box rests on 4 100 pound rails.  It weighs about 35 or 40 full plus a 20 pound cat.  The rails extend out quite far.  The hardest part of the project was building a nice square box inside another one with the right amount of space to accommodate the rails.  I got lucky.  the box slides out smoothly and does not tip at all.

Step 5:

I also added this neat set of pull out shelves since there is no medicine cabinet.

Step 6:

The "passageway" down the left there serves two purposes.  That's a plastic door mat cut to fit in the channel. When the cats exit, they don't bring any liter back into the house -it actually works like a door mat should!  It also prevents my dogs from stealing "treats" -they can't get their big Labrador heads in there.

Step 7:

When the drawer is shut, it works like a charm.  I can open it to scoop into the toilet or replace the litter.  I put the plastic liter box in a 3mm plastic contractor garbage bag and them fill the box over the bag.  Just pick up the sides of the bag and turn it inside out.  No mess!

Hope you enjoy


Step 8:

After seeing I've missed some level of detail (pardon, this is my first submission and I understand that I've taken much for granted), here is some detail on the venting architecture.  The important item to see is the P trap at the bottom of the image in the stack that the box is connected to.  This prevents dangerous gasses from getting into the home.  Water in the traps seal the stack from allowing gasses into the home.  The best way to avoid any possible issue is to have a dedicated vent stack.


Step 9:

Contrast on this image is tuned up to help see detail.  After some consideration I re-opened the wall in the closet, disconnected from the vent stack and redirected the pipe for a dedicated vent stack of it's own.  Typically a bathroom fan uses a four inch pipe but the volume of air being moved is small and the fan is very small so it won't be stressed.  Larger fans require larger vents or you'll stress the fan.  (Imagine a vacuum when you suck up a sock)

Step 10:

This is an image of the finished dedicated stack.  I would have rather kept it in the wall but, that would have been a very invasive project! I sanded the outside of the ABS pipe to rough up the surface for best paint adherence.  The box at the bottom contains the fan.  Since the box comes so far into the closet, I just divided up the remaining space at the bottom with shoe shelves. 



    • Oil Contest

      Oil Contest
    • Woodworking Contest

      Woodworking Contest
    • Make it Move Contest

      Make it Move Contest

    We have a be nice policy.
    Please be positive and constructive.




    I'm just coming across this post now (5 years later, lol). Seems like such a fantastic idea! I'm great with carpentry but unfortunately know absolutely nothing about plumbing but I am dying to try this. I'm going to have to do some homework on step-by-step how-to's. Great job!! Thanks for sharing!

    Thats eally neat, but I feel sorry for the cat going in the dark.. Can you rig up a solar/battery LED lighting system? 1 LED should do the trick, cats can see 6 times better than us in low light.

    2 replies

    Ive heard my cats going in the middle of the night as well in total darkness. They should be fine.

    I considered this but, enough light must get down the side to help them see. I have heard them using the box in the middle of the night so I assume that once they learn their way, they are fine.

    "I can open it to scoop into the toilet or replace the litter." Dont do that. it can kill seals.

    15 replies

    It depends on where the water is sent to first... If your community dumps your sewage into the ocean, then yeah it would be bad. But if they are like most normal communities then they are sending it to a water treatment plant where all toxins are removed before the water is put back into the environment.

    I think your community has problems if they are dumping raw waste into the waterways. Scooping cat poop into the toilet is pretty efficient. If you really oppose, scoop it into a bag and put in the garbage. Or, better yet get a diaper disposal (ie:Diaper Genie). Or you could put it in the garden or compost.

    I said ocean, and yes there are some communities that do that around the world. Instructables is not a USA-only website, please be a little more global in your thinking.

    The proper way to dispose of poo is to bury it in the yard. That's where it wants to go, and that's where I put it. I just dig a hole a couple of feet deep with a post digger, and drop the poo in it. Takes a second, and the garden never has any rabbit problems because they stay away from where there is a lot of cats.


    So, I assume then that you do that with your own poo also?

    I think it would be a safe bet that any place that dumps raw sewage into the ocean, probably doesn't put cat waste up high on their list of things to worry about. Assuming that there is a water treatment plant downstream from your toilet isn't an American viewpoint. It's a modern world viewpoint. Sure there are still plenty of areas on this planet that are not so blessed with modern conveniences, but again, they are not likely to be on this website looking for green solutions to cat poo. It's a bit condescending to ask someone to be more global in their thinking because they didn't address the specific needs of every community on earth.


    Composting yes, and I agree, I would also put it into the toilet if you use environmentally friendly litter.

    But Diaper Genies are incredibly and unnecessarily wasteful things IMHO. There already is enough plastic in conventional diapers, and those machines add an extra layer of scented(!) plastic to the trash.

    If one is worried about the well-being of ocean creatures, the first thing to do would be minimizing the use of disposable plastic products.

    Just my few cents.

    Actually the Diaper Genies are not the problem - it's the diapers that go in them. Therefore, it wouldn't be a bad use for cat poops (unless you train your cat to wear diapers).


    Well yeah I fully agree the diapers are the BIGGER problem, but I don’t think it’s a particularly good solution to wrap them in yet more plastic.

    Basically what I meant to say is, when one is concerned with the health of seals and marine life, then kitty-litter going into the toilet is definitely one of the smaller problems they have to worry about, while disposable plastics are most definitely among the bigger ones – as a lot of plastic ends up in the oceans, even if it has been put into a garbage bin at one point.
    So I wanted to underline and agree with your initial statement: "I think your community has problems if they are dumping raw waste into the waterways."
    I don’t know what kind of kitty litter you would have to use for this form of disposal to be problematic.

    It is actually not a huge issue getting rid of cat poo without any use of plastic really, especially if you put it into the toilet or compost it. So that is why I think a diaper genie for that purpose is wasteful and unnecessary.

    Actually, one reason California Sea Otters are so endangered is because of a disease caused toxoplasmosis. Cats are the main carriers of this disease (cats have few or no symptoms, and up to 50% of cats--and people have it), and people spread it to the otters by flushing the cat poo down the toilet. More wastewater than you'd think goes into our surface waters which is why it is no longer safe to drink any surface waters in the continental U.S. Moral of the story-- Don't flush your cat crap down the toilet!!!

    The main source of toxoplasmosis is NOT cats but contamination from raw or improperly handled meat or seafood...or gardening. Please check your facts to make sure that they are up to date-VERY few cases can truthfully be linked to them anymore (less than a dozen in the many thousands of cases every year). House-only cats that are not fed raw meat and do not eat mice or other rodent pests are not carriers as the disease can't last more than a couple of months in their bodies.

    When I first got my cats my husband (then fiancee) started in on hinting that I would have to get rid of my cats when I get pregnant so I started looking up RECENT data on it to show him. Almost no one practices pristine enough sanitation in the kitchen to keep toxoplasmosis out of their finished food much less out of their drains from just washing up and thus causing it to enter the watershed (overuse of antibacterials/microbials causing resistance is another rant). As long as there are humans and prepackaged raw meat, toxoplasmosis will be pretty widespread. Just washing hands is enough to get it to enter the watershed. There are no easy solutions.

    Just the risk of damage to plumbing is reason enough not to flush clumping litter and I'd be pretty leery of flushing other types of litter.

    Pregnancy/human health specific: many people are already immune to toxoplasmosis due to prior exposure-eating dirt as kids being the main reason. Grilling meat and not being careful to use a fresh plate for the cooked meat is another very common source. Prior exposure/immunity can also be tested for in both humans and cats and apparently there are vaccines for both species.

    I'm pretty sure all our sewage is treated in a manner that does not harm the seals. They first take out the solids, process it and dry it and sterilize it and use it as fertilizer or bury it. Liquids are also cleansed and sterilized and is labeled as "reclaimed water" used for watering parks and other non-food related plants.

    My poop goes down, so so does my cat's poop. If my cat has toxoplasmosis, I probably do to - so it's really indifferent who's toxoplasmosis does down the shitter. Also, if 50% of people have toxoplasmosis then we're a little beyond anything we can do about it. I'm in Wisconsin, with my own septic out in the country, so it's very unlikely to affect the California Sea Otter. Regulations are rarely one size fits all - I shouldn't be held to the same regulations that a city has...

    Yes, toxoplasmosis is an issue with the otters... But, he is in Denver which is pretty dang far away from the ocean. And the main issue is that the water treatment plants are NOT doing their job if this stuff is getting out into the waterways... The main issue is more than likely people dumping kitty litter into the trash, which gets dumped into big piles and then the water table gets polluted that way.

    And if sewage is getting into your surface water, your water treatment plants in your area are SERIOUSLY out of code, and the EPA should be called out. Yes, 'wastewater' goes out into streams and things, but it is not sewage--which is what you are inferring.

    I'd love to sail out into the ocean and make a giant plastic island from all that floating recycleable. From the pictures I've seen it's an absolutely lovely climate there (and worlds better than Wisconsin this time of year)!