The official website of the City of London300 Dufferin Avenue519-661-CITY (2489)3-1-1 (within London)

What Do I Do About A Blocked PDC?

Blocked or Failed Sanitary Lateral

When wastewater from your sinks and toilets leaves your house through your internal plumbing, it flows through a sanitary sewer lateral pipe to reach the City’s main sewer pipe. Blockages along sanitary lateral pipes (from the building to the City sewer main) are the sole responsibility of the property owner/resident of that property.  A blocked or failed sanitary lateral can back up wastewater into your basement, damage your property and presents a health hazard. 

There are a number of reasons why the pipe that connects your home to the sewer in the road (sanitary lateral) may be blocked and/or not functioning properly.  There may be a pipe collapse or obstruction in this pipe caused by: tree roots, grease build up, flushable wipes, pipe deterioration, a toy/object and/or other foreign objects.  All of which could contribute to a partial or full blockage of the pipe.  It is the property owner’s responsibility to maintain their sanitary lateral (building sewer and private drain connection) and regulate what is entering the sanitary sewer system from their property.

If you are actively flooding or recently experienced flooding in your basement, contact the City at 519-661-4570 (Monday to Friday 8:30 am to 4:30 pm) or 519-661-4965 (after hours).  The City will send staff out to the property to determine if the City sewer main (City’s responsibility) under the road is functioning properly or not, at no cost to the property owner.  If it is determined that the City's sewer main is the issue than the City will repair the sewer main.  Depending on the situation City staff may provide the property owner with information on the Basement Flooding Grant Program which includes such items as backwater valves.

Please note that the City of London does NOT share basement flooding information with any external parties and treats this information as confidential in nature. 

If your sanitary lateral pipe is blocked, you should contact a licensed plumber/drainage contractor to determine the  source of the problem.  These contractors typically use camera/video inspection equipment to identify pipe condition and potential problems.  It is important to understand if the issue with your sanitary sewer lateral is located on the building sewer (on private property between your home and the property line) or on the Private Drain Connection (PDC) (within the City/municipal right of way between the property line to City sewer main in the road).  Once it is determined where the blockage is the property owner has the following options:

Blockage is within the Building Sewer (private property side)

Blockage is within the PDC (City property)

  • Call a qualified contractor of your choice (multiple quotes are suggested)
  • Obtain a Permit of Approved Works (PAW)  (519) 661-CITY (2489) Ext 2848 or e-mail


  • If your property is a residential single family, duplex, triplex, 4-plex, 5-plex, or 6-plex, you may request to have it replaced by the City of London.   The City currently offers this PDC renewal service for a flat rate fee of $5,000, which can be paid as a lump sum, or on your property taxes over a 10 year period.   Please call (519) 661-4570 or email for more information.

Cross Bore

If it is determined that there is an obstruction within the sewer lateral, contact Ontario One Call 1-877-969-0999.  On rare occasions another utility, such as hydro, phone, or natural gas, may have inadvertently installed their infrastructure through the sewer lateral making it difficult, if not impossible to allow flows to exit freely through the sewer lateral.  By calling Ontario One Call a FREE inspection will be scheduled to determine if cross boring has occurred. 

Ontario One Call

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