To auger a floor drain, stop all water use, lift the grate, scoop out standing debris, and look for a cleanout plug in the drain body or trap that lets the cable bypass the trap bend. Feed a 3/8 to 1/2-inch drum cable into the outlet with no rotation, spin only at resistance, and advance in short bites. Never auger through a backwater valve flap.
- A floor drain backing up is usually a building drain or lateral problem, not a floor drain problem.
- Many floor drains have a cleanout plug that lets the cable bypass the trap; use it if the plug will turn.
- Hand-drum cable is too thin for most floor drain outlets; plan on a drum machine with 3/8 to 1/2-inch cable.
- A backwater valve in or downstream of the floor drain must be opened and routed around, never punched through.
- Refill the trap after augering, or sewer gas will enter the basement.
01 /Should you auger the floor drain or the main cleanout?
Auger the main cleanout if one exists and is usable, because it gives straighter, larger access to the building drain than the floor drain trap does. Auger the floor drain itself only when the problem is confined to the floor drain (it is slow but nothing else backs up), or when the floor drain is genuinely the best access point in the house.
The distinction matters because a floor drain that fills with water when a toilet upstairs flushes is not clogged in the floor drain. It is the lowest opening in the house, so it overflows first when the building drain or lateral is blocked downstream. Pushing a cable through its trap is the hard way to reach a main-line clog. The main line vs branch clog guide and the Clog Locator help you tell the two apart.
| Symptom | Most likely location | Best access |
|---|---|---|
| Floor drain slow, nothing else affected | Floor drain trap or its short branch | Floor drain (via its cleanout plug if present) |
| Floor drain backs up when washer drains | Laundry branch or building drain | Main cleanout, then floor drain |
| Floor drain backs up when upstairs toilet flushes | Building drain or lateral | Main cleanout or exterior cleanout |
| Floor drain smells but drains fine | Dry trap, not a clog | Pour water in; consider a trap seal |
| Water rises only in heavy rain or snowmelt | Lateral infiltration or surcharged municipal main | Call the municipality first (Calgary: 311) |
02 /What is inside a floor drain?
A typical Canadian basement floor drain is a cast iron or plastic drain body set in the slab, with a removable strainer grate on top and a trap below that holds a water seal against sewer gas. The outlet commonly runs to the building drain in 2 or 3-inch pipe. Many drain bodies, especially older cast iron ones, include a small threaded cleanout plug on the side of the bowl that opens directly into the outlet downstream of the trap.
- Strainer grate: screwed or pressed in. Remove it before augering.
- Sediment bucket: some drains have a removable basket under the grate. Empty it.
- Trap: the U-bend that holds the water seal. Tight enough that heavy cable struggles to pass.
- Cleanout plug: a brass or plastic plug in the side of the bowl. Removing it gives a straight shot past the trap.
- Trap seal device or primer connection: some newer drains have a one-way seal insert or a trap primer tube feeding water to keep the trap wet. Remove inserts before augering, and avoid the primer tube.
- Floor drain backwater valve: a floating ball or flap inside the drain body that closes against backflow. Common in older retrofits.
- Weeping tile connection: in some older houses the foundation drainage was connected to the floor drain or its branch. That perforated pipe is treated differently from sewer pipe; see snaking a drain from outside.
03 /What are the backwater valve cautions?
Never feed an auger cable through a closed or intact backwater valve flap. The flap is a thin hinged gate designed to swing shut when sewage flows backward; a spinning cable can tear it off its hinge, jam it open, or wrap it around the head. Either way the valve stops protecting the basement, and you may not notice until the next surcharge.
- Mainline backwater valve (in the building drain, under an access cover in the basement floor): remove the cover, lift or remove the flap mechanism as the manufacturer describes, and route the cable into the downstream pipe. Reinstall and test the flap afterward.
- Floor drain backwater valve (a ball or flap inside the floor drain): these usually must be removed before the drain can be augered at all.
- Valve closed with water behind it: if the flap is holding back water, opening the cover can release that water into the basement. Pump or bail first, and assume the water is sewage.
Backwater valve rules and any rebate programs differ between municipalities. Check with yours before replacing or adding a valve (in Calgary, call 311).
04 /How do you auger a floor drain step by step?
- Stop water use everywhere
Tell everyone in the house not to flush, shower or run appliances. Turn off the washing machine and dishwasher.
- Protect the area
Lay plastic and old towels, set out a bucket, and open a window or run a fan. Wear eye protection, waterproof boots and the auger manufacturer's recommended gloves.
- Remove the grate and debris
Unscrew the strainer, pull out any sediment basket, and scoop out hair, sand and lint by hand (gloved). Sometimes this alone clears a slow floor drain.
- Find the cleanout plug
Look inside the bowl for a threaded plug. Loosen it with a wrench or a hex key sized to the plug. Old brass plugs seize; heat or penetrating oil may be needed, and a stripped plug may need a contractor.
- Choose the entry
If the plug came out, enter through the cleanout hole, which bypasses the trap. If not, enter through the trap, accepting that you may need a lighter, more flexible cable.
- Set up the machine
Place a drum machine close to the drain so no more than about 30 to 60 cm of cable is exposed. Connect to a GFCI-protected outlet and position the foot pedal where you can reach it without moving your hands.
- Feed without rotation
Push the cable in by hand until it meets resistance. Most floor drain outlets turn within the first metre toward the building drain.
- Rotate in short bites
Start rotation with the foot pedal, apply gentle forward pressure, and advance a few centimetres at a time. If the cable starts to twist or load up, release the pedal and pull back slightly.
- Break through and work the section
When resistance drops and water starts draining, pass back and forth two or three times to widen the channel.
- Retrieve while rotating forward
Pull the cable back slowly with the machine turning forward so debris stays on the head. Wipe the cable as it comes out.
- Flush, refill and reassemble
Run a hose into the drain for several minutes to confirm flow, reinstall the cleanout plug with fresh thread tape, replace inserts and the grate, and make sure the trap holds water.
05 /What cable size works in a floor drain?
Most floor drains need a drum machine with 3/8-inch cable for 2-inch outlets or 1/2-inch cable for 3-inch outlets. A 1/4-inch hand drum is usually too light: it will pass the trap but lacks the stiffness to push to a clog several metres away in larger pipe.
| Situation | Cable | Head |
|---|---|---|
| Slow floor drain, clog near the trap | 3/8 in drum | Bulb or small spade |
| Entry through cleanout plug into 3-in outlet | 1/2 in drum | Spade or C-cutter |
| Clog beyond where the outlet meets the building drain | 1/2 in drum or 5/8 in sectional | Spade, then grabber to sample |
| Roots suspected downstream | Hand off, or sectional with root cutter | Root saw or blade cutter |
For the full sizing logic, see the auger cable size chart. For head choice, see auger cutting heads.
06 /When should you stop augering a floor drain?
- The cable reaches the building drain and stops at the same distance twice.
- The head comes back with roots, clay fragments, rust flakes or sand in quantity.
- Water level in the drain rises while you work, meaning something upstream is still being used or the line is surcharging.
- You find or suspect a backwater valve you do not know how to open.
- The cleanout plug is seized and the trap will not pass cable.
- A strong rotten-egg smell builds up in the basement.
At that point, the job is a main-line job. Read clearing a main line from the cleanout and when augering is not enough, or request quotes and ask whether the contractor will include a camera inspection. The sister site SewerInspector.ca explains what that inspection should show. If the cable would not pass the trap at all, why a drain snake is not working covers the usual causes, and if the floor drain backs up on a regular cycle, how often to snake a main line explains when scheduled clearing makes sense.
FAQQuestions people ask
Why does my basement floor drain back up when I do laundry?
The washing machine discharges a large volume fast. If the building drain or laundry branch is partly blocked, that surge rises to the lowest opening, the floor drain. Treat it as a main line warning.
Can I snake a floor drain with a hand auger?
Only for a clog right at the trap. Most floor drain outlets are 2 or 3 inch, and a 1/4-inch hand cable is too light to push through a clog further along. Use a drum machine with 3/8 or 1/2-inch cable.
Where is the cleanout on a floor drain?
Many floor drains have a threaded plug in the side of the bowl, below the grate. Removing it gives direct access to the outlet past the trap. Not every drain has one.
Can I auger through a backwater valve?
No. Remove the valve's access cover and route the cable around or past the flap as the manufacturer describes, then reinstall and test it. A cable forced through the flap can break it.
Why does my floor drain smell like sewer?
Usually the trap has dried out and no longer seals. Pour water in. If the smell persists with a wet trap, a cracked drain, loose cleanout plug or venting problem may be the cause.
Should I pour chemical drain cleaner in a floor drain before augering?
No. It rarely clears floor drain clogs, and augering through caustic water can splash it onto skin and eyes. If you already poured some, tell the contractor before they start.
NETWORKGo deeper across the HAUSE Sewer network
How to use a drain jetter: a safety-first walkthrough for rental units
How to use a drain jetter or rented sewer jetter: setup, nozzle choice, feeding and pulling hose, and the stop rules that help prevent injection injuries.
PipeCleaning.caDIY vs professional pipe cleaning: where to draw the line
DIY vs professional pipe cleaning: which drain jobs homeowners can do safely, which tools to skip, the injury risks, and when a pro is cheaper.
SewerCleaners.caBackwater valve installation: whether you need one, where it goes and how it is done
Should you install a backwater valve? When one is required, how it differs from a sump pump, how installation works, where it goes, costs and subsidies.