A garage floor drain is meant to serve as the outlet for all the water that enters your garage along with vehicles, gets spilled in your garage, or drains into your garage from the outside. A clogged garage drain can cause a lot of issues from destroyed belongings and tools, to seepage into your home. We explain in detail how to unclog a garage floor drain in this article, covering both standard floor drains and trench floor drains.
If your garage drain is backed up you need to take steps to solve the situation before it gets out of hand. If you don’t unclog the drain dirty water will cause havoc with property damage, mold and vermin. Clogged drains and pools of standing water on a greasy garage floor are a bad mix. Nobody wants to have a nasty slip and fall on a cold, hard garage floor!
Before you start, it’s important to know the type of garage floor drain you’re dealing with.
Types of Garage Floor Drains and How They Work
There are 2 types of garage floor drains – a standard square or round drain and a trench or channel drain.
1. Standard Square or Round Garage Floor Drain
- These type of drains can be of minimum 6 inches to maximum about 1 foot in size. A metal grate is set over the drain entry hole and the garage floor around the drain slopes into the drain area. The slope causes gravity to pull the water naturally into the drain and off your smooth garage floor.
- You’ll see different materials used in these drains. The grill is usually steel, aluminum or brass. It could also be durable plastic. The drain collector and pipes beneath the grill is usually metal or PVC plastic in a residential garage. For commercial use, drains are almost always made of steel or cast iron.
- Square or round drains have a low price tag. They are straightforward to install and simple in design. Newer drains generally work flawlessly when sized correctly and coupled with the right floor pitch.
- The best place to locate a square or round floor drain is the center of the garage floor so that it can capture the maximum amount of water.
2. Trench Garage Floor Drain
- The trench drain, alternatively known as a channel drain or ACO drain, is another type of garage floor drain. It looks like a shallow trench that is concealed with a long metal grate. Trench or channel drains have grates with large surface areas. This significantly reduces the chance of the grate getting blocked and causing a large puddle. The long grate flows into a channel, which then flows down a drain collector and pipe.
- Trench drains work best where there is heavy precipitation, including ice and snow weather, or where there is a lot of water and debris flow, such as a truck wash. They also work in areas that gather lots of leaves. During the winter when you pull into the garage with your car covered in snow, the snow may melt and freeze in the drain. A standard drain can get blocked and back up easily. The much larger trench drain is less likely to get backed up.
- Trench floor drains are more expensive but more clog-resistant. Water will flow down them and into the drain collector without clogging frequently. A simple cleaning every few months is all they need.
- Trench drains are usually located along the perimeter of a garage or at the garage opening. The garage floor will slope toward the drain, leading water and spills to naturally move away from the inside toward the outside of the floor.
Step-by-Step: Unclogging Your Garage Floor Drain
Now that you know about the different types of garage floor drains, let’s get started.
Tools Needed to Unclog a Garage Floor Drain
You will first need to gather some necessary tools. These are the most important ones to do the job effectively.
- Cold chisel
- Pipe wrench
- Wet/dry shop vacuum
- Plumber’s drum auger or snake
- Teflon tape
- Penetrating oil
- Hand shovel
- De-icing solution (for winter ice clogs)
Unclogging a Round or Square Garage Floor Drain
Step 1: Unscrew the drain cover. In some cases if the concrete is covering the edge of the drain cover, you may need to chisel the concrete to get to the screws.
Step 2: Clean out the drain and look through the vertical hole to see if there’s an obvious clog. The hole going straight down is linked with a U-shaped trap below the drain that’s filled with water. The standing water in the trap collects debris and prevents sewer gases from backing up into the garage. The trap is the most common place to get a clog.
Step 3: Start sucking out the gunk from the main drain trap using your wet-dry shop vacuum. Put the vacuum hose down the center hole where the water flows into the trap. This will pull whatever gunk is stuck there out. You will likely find screws, bolts, wood chips, plastic wrappers, leaves, dead bugs and all sorts of detrius from years of garage projects. (You can thank me now for suggesting you vacuum the trap out 🙂
Step 4: Pour a bucket of water into the drain. If the water flows quickly out of the drain, you’ve gotten most or all of the clog out of the trap with your wet / dry vacuum. You’ve unclogged your floor drain and can reinstall the drain cover grill.
If the water still moves slowly, try vacuuming again to see if you can pull more of the clog out. Repeat with another bucket of water. If it flows down the drain quickly, you’re done. If you do this several times and the water still doesn’t flow down quickly, then you probably have a clog in the main drain line. Go to the next step.
Step 5: Next to the main drain hole in a typical garage floor drain you’ll find a clean-out plug. This plug covers an auxiliary pipe that connects to the main drain line downstream of the U-shaped trap. When you unplug this it allows the water to pass by the trap and go directly into the main drain line and on to the sewer.
Remove any debris in the drain and take the clean-out plug off. Plastic or rubber plugs generally come out easily, but may come apart if they’re really old. Metal plugs usually require a pipe wrench and a bit of banging with a hammer to loosen.
If the plug is metal and you can’t budge it try penetrating oil to get it to loosen up — the last thing you want to do is crack the drain housing! If the plug is metal and the threads strip, you can just replace the plug with a rubber expansion one.
Be careful — you don’t want to unplug this hole if there is still debris in the drain because it could cause another clog downstream in the main line.
Step 6: Get out your plumber’s auger or snake. Insert the tip into the clean-out pipe and start turning the cable and feeding it down the pipe.
Step 7: When you reach the clog, give it a few light tugs to make sure the clog is attached then pull it out. If you run into a blockage that feels hard then it’s probably a pipe elbow or tee. You need to keep manipulating and feeding cable in until you reach the clog. Clogs will have some “give” to them and they resist being pulled out of the pipe.
Step 8 : Repeat the process of inserting your plumber’s auger or snake into the clean-out pipe and pulling out clog chunks until it’s gone.
Step 9 : Wash the drain again with a bucket of water and replace the clean-out plug. If the plug is metal you should wrap the threads with teflon tape to ensure it seals correctly and doesn’t get stuck.
Step 10 : After you close the clean-out pipe, pour some more water into the drain. This will show if the drain is completely flowing and will refill the U-shaped trap so sewer gas won’t back up into your garage.
Unclogging a Trench Garage Floor Drain
NOTE: Trench drains are notorious for freezing up in the winter. If you have a wintertime ice clog you will need to use de-icing solution to melt it and release the debris before you can pull the clog out.
Step 1: Unscrew and/or lift out the grate sections covering the drain channel. You may need to use a hook, screwdriver or claw to grab or lever up the grates and lift them out. Depending on the design, these grates may be screwed in or they may lift out directly.
Step 2: Scoop out all the dirt and debris from the drain channel with a hand shovel. You don’t want to wash it further down the drain, adding to the clog. As you clean out the drain channel you may be surprised at the goodies you find!
Step 3: If your trench drain leads to a drain collector then clean out the debris from the collector. The collector area is usually the first thing that gets clogged.
- Some garage trench drain systems lead out through an open hole in the wall, under the garage door, or into a horizontal pipe that runs through the wall. This junction is usually where clogs build up. You can simply push the clog from the outside of the wall back into the garage with a broom stick or pipe to clear things up, then move to the last step.
- If you have a clog in the winter, get out your de-icing solution and pour that along the channel and into the main collector to melt the ice before you get started.
Step 4: Remove any grate over the main drain hole and look into the pipe to see if you can find the clog. The drain pipe may lead down to a U-trap or it may run horizontally outside the garage to the exterior. This trap or down pipe is the most common place to get a clog.
Step 5: Suck out the gunk from the drain pipe using a wet-dry shop vacuum. Put the vacuum hose down the center hole where the water flows into the trap and turn it on full power. You might find screws, bolts, wood chips, candy wrappers, golf balls, leaves, dead rodents and all sorts of not-so-appealing gunk. (thank heaven for wet vacuums!)
Step 6: Pour a bucket of water down the drain. If it flows quickly down the drain, then you’re done. You can skip to the last step.
If the water doesn’t flow out freely, then you probably have a clog in the main drain pipe. You will need a plumber’s auger or snake to get the clog out. Go to the next step.
Step 7: If the drain has a clean-out plug, remove that (SEE ABOVE).
Step 8: Twist and feed your auger or snake cable into the clean-out pipe until you find the clog (SEE ABOVE). Make sure it’s attached and start pulling chunks out until you can’t get any more out.
Step 9: Pour another bucket of water down the drain. If it flows freely, you’re done. Replace the clean-out plug and go to the last step.
Step 10: If the drain is still clogged, then it’s likely something heavy got into the drain pipe and is lodged there. In this case you should call a professional plumber — they have tools and techniques that you don’t — and an insurance policy to cover broken pipes. If you try to force the clog down the pipe yourself you could damage the pipes and end up with a major repair job.
Step 11: Replace all the grate sections covering the drain channel.
Using Chemical Drain Cleaners to Unclog a Garage Floor Drain
Aside from the hands-on mechanical methods above, it’s also possible to unclog a garage floor drain with liquid chemical drain cleaners. This has the benefit of being a hands-off operation — just pour the solution in and wait.
However, there are a few things to be aware of with using these chemicals:
- Drain cleaning chemicals are toxic. You don’t want to use them, fail, then try to clean out the drain manually soon afterward. This is a sure way to burn your skin, eyes and/or lungs. Follow the safety directions on the bottle!
- Chemicals cannot break down metal, heavy plastic or wood chunks. These things are often found in garage drain clogs because they are byproducts of having cars, bikes and woodworking projects going on in the garage. So the chemicals may not work at all, no matter how much you put in.
- You should never mix different chemicals. Do not mix a bottle of chemical drain cleaner with vinegar and baking soda, or any biological drain cleaner. You could end up with a toxic chemical reaction in the worst case, a gummy substance that just adds to the clog, or the chemicals will neutralize each other. Follow the directions on the bottle and don’t mix with anything else besides what the manufacturer says!
More Info: How to Keep Garage Floor Drains From Clogging Up
Floor Slopes and Low Points
A garage floor is generally designed with the drain type in mind. The floor of the garage, including the driveway, are slanted toward the drain (or drains) to ensure water flows easily into the drain hole or trench. The garage floor should slope toward the drain a minimum of ⅛ inch per foot.
This slope causes gravity to collect all the dirty water and debris in the area of the drain. This also explains why garage floor drains often get clogged — because they collect debris like small bolts, dust, plastic and leaves that flow into the drain from a large floor area compared to the drain’s size.
Round / Square Floor Drains
Standard garage floor drains located in the middle of the garage will clog when large objects, grease, sawdust and other detrius gets stuck. Here are some tips to prevent this type of drain from clogging up:
- Most residential garages have a single simple square or round type of drain. This are located in the center of the garage, in a corner, or near a laundry machine or sink. Make sure you keep the area well-swept and don’t let rags, soap, grease or sawdust collect on the floor near the drain.
- The drain collector (the part with the grill over it) is usually round and set into the concrete floor. The grill or grate either sets into the collector, or is screwed down. Make sure you keep the grate clear of debris. A simple shop towel or pieces of tape, cardboard or plastic wrappers can easily block the grate and cause a flooded garage.
- The drain pipe is normally set in a trench beneath (or in some cases encased in) the garage floor. The drain pipe flows downhill to the main sewer line outside the house. If the grill is clear but the drain is flowing slowly, try clearing it up with a liquid drain cleaner.
- Depending on the local building code, the drain pipe may flow into a collector designed to trap grease and chemicals so they don’t flow into the main sewer line. This helps restrict chemicals and oil that may drip from cars from entering the water supply. These types of traps are more common in commercial garages. If your drain starts flowing slowly and backing up often, but you can’t see a clog in the interior drain collector, check the outside trap and any grates covering it. It’s a good chance the trap is full or the grate is blocked, causing sewage to run back up into your garage.
Trench Floor Drains
- Most commercial garages and expensive homes in snowy climates have trench or channel drains. They are located along the main garage door, and often around the perimeter of the garage. They may also criss-cross the floor if the garage is large. Trench floor drains are great at removing water and debris from the garage floor, but they will often back up at the collector point.
- Trench drains are long, shallow channels molded into the floor. They can be molded in sections out of concrete using a form. Alternately, the can be purchased separately and set into the floor when it is poured, or a channel cut into the floor and the drain cemented or glued in. Make sure the channels are properly set into the floor. If one starts to lift, it will cause a backup at the nearby joint.
- The trench or channel slopes downward toward the main drain. The floor is also angled toward the drain — this means it will either slope down toward the door, or have a crown in the floor that causes water to run off toward the walls. If your garage floor isn’t sloped properly you will find water pooling on the floor. You can cut small channels with an electric grinder or power saw with a masonry wheel that flow the pooled water into your trench drain.
- Trench drain grates lay down in a recessed notch inside the top of each channel. They are made of steel, brass, iron or strong plastic. The grates may be screwed own or just set in place with gravity. Lengths range from 18 inches to 3 feet. Keep these grates clean of rags, wrappers, old tape, cardboard, paper and any other flat items.
- The main drain collector and drain pipe sit below the surface of the garage floor, even with the bottom of the trench. This allows the drain channel to fill up with a lot of water and slowly drain out, rather than letting the water pool on the surface of the floor as a standard residential drain can do. This collector is usually the first place a garage floor drain gets clogged. Keep the collector free of debris.
- The drain pipe flows downhill to the main sewer line outside the building. Commercial and industrial buildings usually have some sort of trap outside the building to catch debris, chemicals and grease to prevent it flowing into the main sewer system. If your drain flows slowly but there is no sign of a blockage inside, go outside and check the trap. It’s a good chance the trap is full or the grate is blocked, causing water to back up.
Garage Floor Drains Installed Retroactively
Older homes and small commercial buildings may not have had any garage floor drain installed when they were built. The drain may have been installed later to deal with a frequent flooding problem, or to meet new building codes.
It is very common for these drains to be installed incorrectly. Few owners are willing to rip up a garage floor and re-pour it with the right slope. The slope of the floor is usually too flat. The drain will often be undersized. The drain and drain pipe are often too low in relation to the main sewer line, leading to frequent backups and odor problems.
In the best of circumstances, the new drain would be cut into the slab, positioned and connected to the main sewer line with the right pipes and slope, a U-shaped trap installed, perhaps a back-up valve, and a clean-out pipe included. But that’s a “best case scenario” — not what you normally find!
Many owners of old buldings cut simple open channels into the floor leading to the drain. The garage floor slab is not sloped at all — instead the drain is recessed into the floor. These drain channels often struggle to collect and move water and debris out of the garage. This can lead to mold and instects, and creates issues with rolling things across the floor and tripping on the channels. But they are better than having standing water.
You can easily install a garage floor drain in your new garage following the guidelines we shared here. You can also manage to have them if no built-in floor is present in your existing garage. Decide the type of floor drain, install them and keep on doing regular maintenance to avoid the frequent drain backing up. If somehow, the water starts logging, feel no stress. Proceed step by step (basic, intermediate and finally, advanced methods) on your way to unclog garage floor drain.