How to fix a drain that is overflowing into another drain?

 
Safety Precautions
 

• Before starting any work, switch off the water supply to minimize further overflow or accidental spills.
• Wear protective gloves and goggles when handling drain cleaners or if you expect to be exposed to contaminated water.
• Ventilate the area or wear a mask if using chemical drain cleaners.

 
Identify the Problem Area
 

• Determine which drain is overflowing into the other and inspect both the primary and the secondary drain for obstructions.
• Note if the overflow happens only when water is running in one fixture or if it is a constant issue, as this will help isolate a blockage or backflow problem.
• Check for any unusual sounds or slow draining that might indicate a buildup of debris in the pipes or traps.

 
Examine the Plumbing Layout
 

• Review a diagram or map of your home's plumbing if available to understand where the drains connect.
• Locate the connection points where the problematic drain meets the other drain, as these junctions are common spots for clogs.
• Watch for any shared items such as P-traps and vent pipes that could be contributing to the issue.

 
Clear Visible Blockages
 

• Remove any visible debris or buildup from the drain openings by using your hand (with gloves) or a tool designed for removing clogs.
• If there is standing water, use a cup or a small bucket to remove it gently before attempting further cleaning.

 
Use a Plunger Method
 

• Position a plunger over the affected drain to create a tight seal.
• Move the plunger up and down vigorously to generate suction and pressure that may dislodge the blockage between the drains.
• Test by slowly turning the water supply back on to see if the overflow has been resolved.

 
Employ a Drain Snake or Auger
 

• If plunging does not clear the blockage, insert a drain snake or auger into the drain opening.
• Push slowly until you feel resistance, then rotate the snake to break up or latch onto the blockage.
• Pull the obstruction out or push it through if possible, then run water to flush out any remaining debris.

 
Clean the Overflow Drain Connection
 

• Check the secondary drain where the overflow is occurring for similar blockages.
• Use a brush or cloth to remove accumulated grime around the drain opening and ensure there is no buildup connecting the two drains.
• If the drains share common piping, consider using a chemical drain cleaner that is safe for your pipes, following the manufacturer's instructions.

 
Test the Drains
 

• Once both the primary and secondary drains appear clear, slowly turn the water supply back on.
• Monitor both drains closely to ensure water is flowing properly without overflowing into the other drain.
• If the problem persists, it could indicate a deeper blockage or a venting issue in your plumbing system.

 
Consider Additional Measures
 

• If recurring issues occur, inspect the vent pipes attached to the drains; blocked venting can cause back pressure.
• Conduct periodic maintenance by flushing the drains with hot water and safe drain-cleaning solutions to prevent future blockages.
• Review any changes in water pressure or usage that might affect the flow through shared drain lines.

 
Seek Professional Help
 

• If none of these steps resolve the overflowing issue, it's advisable to consult with a licensed plumber.
• A professional can use specialized equipment, such as a video drain inspection camera, to locate and diagnose the root cause of the blockage.
• They can also verify that your plumbing system meets local codes and make recommendations for long-term maintenance or upgrades if necessary.

 

Plumbing challenges can vary by region, and in areas like St. Louis and Nashville local factors may influence drain performance.