Prevent Sewer Backups

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What NOT to Flush [pdf]

Troubleshooting Sewer Backups [pdf]

Clean up the Backup [via Seattle Public Utilities]

TAKE BACK YOUR MEDS safely - King County's safe disposal program.

REMOVING TREES? You may need a permit. Check tree removal requirements for your city:

DOING SEWER REPAIR WORK? Contact (425) 398-4401 or to learn what permits are required.


You own the sewer line on your property.

Because any issues that occur on private plumbing - including the underground lines - are the property owner's responsibility, it's important to know the location and condition of your pipes, how to prevent damage, and how to troubleshoot problems when they occur.

 Diagram showing the division of sewer maintenance responsibility at the edge of the public right of way
NUD manages all sewer issues that occur in the public right of way or public sewer easement. But property owners are responsible for all problems that occur on the private sewer lateral on their property side.

Protect your home - and our environment.

All "used" water ends up in the same place - the public wastewater system. This means that issues that occur on one home's sewer line can actually create problems for other homes, and the public system.

This page is intended to provide you with key best practices to protect your sewer line, to prevent costly sewer backups and environmental damage.

Please contact us - any time, and first in emergencies.

We are here to help. If you face a sewer backup, please contact NUD - our main line is staffed 24/7. We will provide whatever assistance we can, but we also must make sure the public system is protected. If you have any questions about the information on this page, call us at (425) 398-4403 or email


  1. Know what NOT to flush.
  2. Know your sewer - it's material, age and location.
  3. Plant wisely to prevent root intrusion.
  4. Catch problems early - by simple observation, or video inspection.

What happens to wipes in your pipes? Video published by the Water Environment Federation.

1. Don't Flush Trouble

Your sewer line, and the public wastewater system, are only designed to handle two things (besides water):  human waste and toilet paper. All other waste should be disposed of in the trash.

WORST items to flush:

Disposable wipes - any kind, even if the label says "flushable." Wipes don't break down in the sewer line. They are becoming one of the #1 causes of sewer backups.

F.O.G. (fats, oils, and grease) - F.O.G. products cool and congeal down the line, sticking to pipes and other flushed debris like wipes. F.O.G. waste in the sewer contributes to an estimated 50% of sewer overflows.

The London Fatberg, grease and wipes clogging the sewer
The London "Fatberg" (via NPR):  when cooking grease and wet wipes block a major sewer system, it endangers health and costs millions.
NUD sewer cam showing grease backup
The problem hits close to home:  this screenshot from NUD's sewer cam shows a grease blockage in Kirkland.

More trouble for toilets:

  • Feminine sanitary products
  • Diapers or nursing pads
  • Dental floss
  • Paper towels or tissues
  • Hair
  • Cotton balls or Q-tips
  • Condoms

More trouble for the environment:

Flushing wipes, grease and other trash may be more convenient at the moment. But in the long run, it brings more trouble - for you, our neighbors, and our environment. 

Remember:  If it isn't water, human waste, or toilet paper, please put it in the trash, not down the toilet or drain!

2. Know Your Sewer Line

Sewer lines have a lifespan. The more you know about your home's sewer - its material type, age, and location - the better you can help prevent problems. Northshore Utility District can supply you with your sewer line diagrams - also called sewer asbuilts. Contact us at (425) 398-4403 or to receive a copy.

Some issues to consider are below:

Material types:

Your sewer asbuilt will tell you what type of sewer pipe you own. Most homes in this area built before 1970 used primarily clay or concrete sewer pipes. Concrete pipes have an approximately 50-60 year life span; clay can last longer. However, both of these pipes are typically constructed with more line joints, which can be vulnerable to root intrusion. Additionally, concrete pipes are more susceptible to erosion from the acids in flushed fats, oils, and grease. Clay pipe can become more brittle over time - so you should exercise caution when cleaning this type of pipe. Homes built after 1970 typically have plastic, or PVC, lines, which can last longer than clay or concrete.


Your sewer line's location can affect the pipe's condition in several ways.
  • If your sewer line runs near trees or shrubs, you will likely have to manage root intrusion. You may want to consider removing plants, or doing a regular video inspection of the pipe's interior to get ahead of root problems. 

  • If your home is at a sewer end zone - i.e. at the end of a culdesac or private drive - you may have less wastewater flow to flush materials through. In addition to following best practices about what not to flush, you may also need to take precautions with the amount of toilet paper flushed. Low-flow toilets may not be the best solution for your property.

Clean-out access:

Clean-outs installed along private sewer lines allow easier access to scope and address backups or other issues. When maintaining your landscape, keep clean-outs free of obstructions that can prevent easy access in emergencies. Sometimes clean-outs are installed below grade - if you need help locating these, contact NUD to request your side sewer asbuilts.

3. Plant Wisely to Prevent Root Intrusion.


As discussed above, if your sewer line is located near existing trees or shrubs, root intrusion will inevitably become an issue.

If you are considering planting on your property:

  • Make careful measurements to avoid interrupting the underground pipeline. A tree or shrub's root span below ground is typically the same as the span above ground.

  • Plants with non-invasive root structures are the safest choice. This plant list provided by King County shares recommendations for which trees and shrubs to plant near utility lines.   

If you are considering removing trees on your property:

4. Catch Problems Early

 Sewer cam showing tree roots growing inside pipe
Homes with older concrete or clay sewer pipes, with multiple pipe joints, are particularly vulnerable to root intrusion at the jointures.
 Sewer grade problems
Video inspection of the sewer line can uncover sewer slope issues, such as a belly in the line, a negative slope area, which will prevent proper wastewater flow.
Many sewer backup situation can be prevented by following best practices about what not to flush. But your line may have complications due to its age, material, location, or other issues like a belly in the line or a low gradation that prevents proper flow. Your best defense is to know these issues by taking a video inspection of the line, watch carefully, and address small problems before they become bigger ones.

Sewer line video inspection:

Video scopes of your sewer line can cost about $200. But this investment may save you thousands down the road if it helps you catch issues. If you have trees growing near your sewer line, taking a video inspection can be especially important to identify root intrusion early. Most plumbing contractors own sewer camera equipment.

Tracking problems on your line:

A few issues can indicate problems on your sewer line:

  • If your fixtures begin draining more slowly, it can indicate a backup somewhere on your sewer line. You should investigate as soon as possible.

  • If you notice a greener or faster-growing area of grass in the path of your sewer lateral, it could indicate a crack or break in the sewer line. Watch the drainage of your interior fixtures carefully. If you have trees growing nearby, you may want to perform a video inspection to identify possible root intrusion.

If you experience repeated slow drainage throughout your home, or at the lowest level in your home, such as a downstairs toilet or tub, contact NUD for assistance - call (425) 398-4403 or email If you experience a sewage backup, please call us immediately.

Making Repairs to Your Sewer:

To make any repairs or changes to your private sewer system, you must obtain a permit from NUD. Since your side sewer is connected to the public system, NUD must inspect all sewer work. This helps homeowners as well; NUD will document all sewer line changes on your asbuilt. In most cases, the permit is free.

If you have sewer line issues, you have a few options:

  • Relining the pipe can be more cost effective than replacing the line - depending on the type of landscaping the pipe runs through, and how deep the line runs. The relining process inserts a new pipe, called a "cured in place pipe" (CIPP), inside the old one. The CIPP felt and resin material has an approximate 50-year life span. Pipe liners are installed via one access point, typically at the shallowest point near your foundation, potentially a less intrusive option than digging up and replacing the entire line.

  • Replacing the entire sewer line, which in some cases may be more cost effective.

  • Replacing one damaged section, appropriate if your pipe has gradation issues, such as a belly in the line.

In all cases, you should consult a certified contractor and gather more than one estimate. NUD can provide a non-comprehensive list of contractors approved to do work in the area - call (425) 398-4401 to access this list.

To learn what permits you need for your repair work, contact NUD's engineering permitting office at (425) 398-4401, or email

Please contact us if you have any questions about the information on this page. You can reach our Operations Department at (425) 398-4403 or, or 24/7 in emergencies at (425) 398-4400.