Garage Floor Drain Ideas | This is a simple illustration of a modern side-outlet garage floor drain. There's a small area at the bottom of the drain to capture sand, dirt, and debris so it doesn't clog the drain pipe.
Garage Floor Drain Ideas - Time Tested Technology
The inspiration for this column came from unexpected comments about a brief mention of garage floor drains in my December 1, 2019 AsktheBuilder newsletter and my December 9, 2019 AsktheBuilder newsletter.
The house I grew up in had a garage floor drain. The concrete floor was sloped like a giant shallow funnel so all water that got on the concrete flowed to the drain. That floor drain never caused any issues in all the years I lived in that home.
My current house doesn't have a garage floor drain. In fact, there's not even one in my all-important mechanical room where the boiler and water heater are located. You know at some point you'll have a leak in this room for goodness sake! I don't think plumbers in New Hampshire know about floor drains. My garage floor is sloped from the back of the garage to the doors.
I live in the snowy and cold Northeast USA where ice and snow are as common in the wintertime as whoopie pies in the grocery store. Water flows to the garage doors and puddles when snow and ice melt from my car and truck. Some seeps under the door and on cold days the garage door weatherstripping freeze to the floor!
It's ridiculous, as are many things in life! A floor drain or two in my garage would prevent this madness.
Silly Building Code Revisions - They're NOT Always Right
It's insane! The building code was altered some time ago prohibiting garage floor drains in certain cities and towns. The reasoning, I'm told, was that spilled gasoline and oil would cause explosions, death, and destruction.
Can you think of the last time in your city or town that you read about or saw on the local TV news that a house was destroyed and people killed by a garage floor drain or gasoline spilled in a garage without a floor drain?
Yeah, I thought so.
Did you know you can make your own silly TV news graphics like this one? Yes, you'll have eaten, drank, slept in a hammock, went kayaking, played epic games of ping pong against your nemesis, and maybe opened a prize or two before you ever hear about a garage explosion caused by a frivolous floor drain.
Newsletter Response - "Where's the Oil Separator, Tim!"
One or two subscribers who read my newsletter wondered if I had a special way to clean out debris from the floor drain. I've been a master plumber since age 29 and you bet I took that into consideration. Go back up and look at the illustration to see how debris is captured and prevented from entering the drain line.
It's important to realize you need to clean out the debris periodically so it doesn't accumulate to the height of the drain pipe. Look at the following illustration to understand how old floor drains, like the one in the house I grew up in, were piped.
This is how hundreds of thousands, perhaps millions, of floor drains are piped. You can see that the bottom of the trap can fill with sand and debris. You can't get your hand down the pipe, but you can insert the end of a wet-dry vacuum hose!
You can see old floor drains are much like the p-traps under your bathroom or kitchen sink. It's easy for them to get clogged.
Why Put Traps in Garage Floor Drains?
Traps should be incorporated into garage floor drains to prevent vermin from entering the garage. This is especially true of drains that are piped directly outdoors on the land just outside the garage.
I'd never connect a garage floor drain to a septic system because I don't want any oil or mystery chemicals stored in the garage to have a chance to get into the septic tank.
It's unlikely that a plumbing inspector would allow a garage floor drain to be directly connected to a municipal sewer system. At the very least it should only be connected to a municipal stormwater drainage system.
The traps should be under the garage floor to help prevent them from freezing in cold climates. Water frozen in a p-trap will stop the flow of water out of the garage.
In April of 2019, I had to re-plumb the floor drains in my daughter's garage. The contractor who put them in didn't include a trap and he just ran the drainpipe to the footing drain. This allowed radon to fill the garage like hot air fills a political debate.
Look at how I installed the drain so it has a vertical riser that allows you easy access to the p-trap. That capped pipe is flush with the concrete floor now that the slab is in place. In addition, I made sure the drain line leaving the floor drain on the right was a straight shot into the p-trap for the same reason.
Quite a few subscribers were wondering where the drain water goes from the garage and if I had installed an oil separator.
The pipe drains to the ground outside about 40 feet from the garage door. I didn't install an oil separator and it's not required by the code.
Let's Apply Common Sense
What do you think the odds are of more than a tablespoon of oil reaching that floor drain on any given day? When was the last time you had a massive oil spill in your garage? If you did, did you clean it up or just hose it outside?
How many total gallons of oil drip from trucks, cars, and heavy equipment up on Mt Desert Island each day where my daughter will live?
What happens to that oil? Is most of it broken down in the soil at the side of the road and/or does a certain amount evaporate over time? Think about where you live. Think about how much oil is spilled on the ground in your town or city each day.
Much/most of the motor oil you put in your car or truck comes from the ground in the first place. It's as organic as it gets. Yes, it almost always needs to be extracted from bedrock, but there are natural seeps.
The point is most responsible people will clean up spilled oil in a garage. Most probably put down old cardboard under a tired engine or transmission.
Lastly, Mother Nature has great healing properties. She can and does clean up oil spills. It may take her more time than you would like, but She gets the job done.
Oil Separators
Let's imagine you're very concerned about getting oil on your land or into the ecosystem. You can install an oil separator as part of your drainage system. You just have to remember to get the oil out by pumping it or scooping it into bottles that you then drive to the recycle center.
It's important to realize the oil in the separator will be underground. You'll be on your hands and knees dealing with it.
If you have strong feelings about garage floor drains and oil, I urge you to spill your thoughts below in the comments. I moderate all comments to prevent SPAM, so it could take a day or two for your comment to appear. I publish all comments that aren't SPAM.
