Why Is My Floor Drain Backing Up? Causes and Solutions

A backed-up floor drain is a common plumbing problem that can cause messy and unhealthy conditions in any home. If you notice standing water, sewage odors, or gurgling sounds coming from floor drains, this likely means there is a clog or blockage in the pipes below.

Identifying why your specific floor drain is malfunctioning is the first step to getting it fixed. Here are some of the most common causes of floor drain backups and how to get your drains flowing freely again.

Causes of Clogged Floor Drains

There are several reasons you may be dealing with a backed-up floor drain:

1. Buildup of Debris, Grease, and Other Gunk

Over time, floor drains can accumulate all sorts of gunk, including hair, food particles, grease, soap scum, and other debris. This material collects on the drain walls and hardens, slowly blocking water flow. Kitchen and bathroom floor drains are especially prone to greasy buildups.

Pouring grease, oil, or fat down the drain is a surefire way to cause clogged drains. As these substances cool, they stick to pipe walls. Fibrous material like hair can get tangled in the grease, making clogs worse.

2. Clogged or Damaged Drain Pipes

The drain pipe carrying wastewater away from the floor drain could be clogged with years of accumulated gunk. Tree roots, if present, may have invaded and blocked the pipes. Cracked, misaligned, or sagging drain pipes can also obstruct water flow.

If the main sewer line that your floor drain connects to is blocked, this would cause backups. A drainage system overloaded with wastewater can also lead to slow-draining floor drains.

3. Issues with Drain Vent Pipes

Vent pipes remove sewer gases from drainage systems. They balance air pressure so water flows freely down drains. If the vent pipe attached to your floor drain clogs up or breaks, this can cause backups.

4. Improper Slope of Drain Pipes

For optimal drainage, pipes should slope 1/4 inch per foot. Flat or sagging pipes allow wastewater to pool, leading to clogs. Sections with reverse slope cause even worse drainage problems.

A floor drain itself may not be correctly sloped. Ideally, the drain should sit at least 1/8 inch lower than the surrounding floor. If it's flat or higher than the floor, water can't empty into it.

5. Leaky Plumbing Fixtures

Leaky sinks, tubs, showers, or toilets can overload drainage systems. This adds excess water that can back up floor drains. It's important to fix any drips and leaks throughout your plumbing system.

6. Malfunctioning Sump Pump

Basement floor drains often connect to a sump pit and pump. A sump pump removes groundwater before it floods your basement. If the pump is clogged or not working right, water can back up through floor drains.

Unclogging a Blocked Floor Drain

Tackling a clogged floor drain right away helps get your plumbing flowing again. Here are some DIY methods to try:

• Pour very hot water down the drain to melt grease clogs.
• Use a plunger or drain snake to break up and dislodge clogs.
• Mix baking soda and vinegar and pour down the drain - the reaction can help dissolve gunk.
• Remove the drain cover and clean out any debris caught in overflow holes.
• Take apart the P-trap beneath the drain and clean it thoroughly.

If you use chemical drain cleaners, take care to follow directions. Only use in floor drains designed for these products.

Preventing Floor Drain Backups

While occasional clogs are inevitable, you can take steps to prevent floor drain backups in your home:

• Install drain covers or screens to keep out hair and debris.
• Avoid pouring grease or harsh chemicals down drains.
• Use a drain strainer in the kitchen sink.
• Pour hot water down drains weekly to clean inside of pipes.
• Use enzyme cleaners or baking soda regularly to break up gunk.
• Keep debris out of bathroom and laundry floor drains.
• Fix any leaky plumbing fixtures.

When to Call a Professional Plumber

DIY drain cleaning is an economical first step for clogged floor drains. But if you've tried everything and the drain is still backed up, it's time to call a pro. Plumbers have the high-powered tools and expertise to fully clear clogs and identify underlying issues. Call a plumber if:

• Snaking the drain doesn't solve the problem.
• Water starts backing up other drains or toilets.
• The clog causes flooding in your home.
• You suspect damaged, leaking, or improperly sloped pipes.
• Outdoor sewer lines or city main lines are likely blocked.
• Your vent pipe needs inspection.
• You want to have pipes inspected with a sewer camera.

Professional Drain Cleaning Methods

Plumbers have various methods to clear stubborn drain clogs and get your system flowing freely again:

• Hydrojetting - Uses high-powered water jets to scour pipe interiors and blast away years of built-up gunk.
• Augers - Feed a spinning auger down the line to break up and pull out clogs.
• Pipe Inspection - Send a camera down lines to locate collapsed, broken, or root-invaded pipes.
• Chemical Drain Cleaners - Industrial-strength formulations dissolve organic material and grease.
• Pipe Repairs - Plumbers can fix damaged drain pipes and improper slopes.
• Pipe Replacements - Severely damaged drain lines may need full replacement.

Fixing an Improperly Sloped Floor Drain

If your floor drain has incorrect slope, a plumber may recommend:

• Re-routing the drain line to create proper downward slope.
• Installing a small sump pit and drain pump system.
• Adding a backwater valve to prevent sewage backups.
• Raising the drain pipe opening using spacers.
• Using shims during drain installation to adjust slope.

For drains requiring frequent plunging, a plumber can also install a drain trap primer. This valve delivers water to drain traps, preventing evaporation that can clog sinks.

It's critical to keep basement floor drains clear to prevent flooding. Other tips include:

• Installing overhead sewer trap primers in basement plumbing.
• Using a sewer backflow preventer valve on main drainage lines.
• Sealing foundation wall cracks and gaps around pipes.
• Ensuring floor drain traps always have water in them.
• Improving landscape grading to divert stormwater from your home's foundation.

Catching a clogged floor drain early and taking steps to prevent future backups will help keep your home's plumbing running smoothly.