7824 Mukilteo Speedway
Mukilteo, WA  98275


Wastewater FAQs

Is it okay to dump grease down my house drains?
No, dumping grease down your house drains will cause grease buildup in your own drain lines. Some people believe that if you mix hot water with the grease, it will not clog your lines. While this may not clog the lines in your immediate house, by the time the grease gets to your sewer pipe it will have cooled enough to build up. Keep in mind, you are responsible for the maintenance of your side sewer and calling out a plumber for this type of maintenance can be very expensive.

Is it okay to dump car oil down the sanitary drain system in my house?
No, oil causes the filtration system at the treatment plant to fail and the filtration system must be cleaned and replaced, causing thousands of dollars in damage.

Is it okay to flush plastic items down the toilet?
No, flushing plastic items and other non-biodegradable material, such as many brands of baby-wipes, down the toilet causes problems in sewer lines. The material will hang up in your line and cause blockages. If the material reaches the treatment plant it will cause problems in the treatment process as well.

What is this manhole for in my back yard?
The manhole is used for access to the system for maintenance and cleaning.

What should I do if I see liquid flowing out of a sewer manhole?
Contact the District at 425-355-3355.

How are sewer lines maintained?
Sewer lines are systematically cleaned using high-pressure jet nozzles that scour the sewer lines of grit and grease debris that is then vacuumed out and disposed of at the treatment plant. An inspection camera is also used to view the inside of the sewer lines for evaluation purposes to determine line repair or replacement.

How does the treatment process work?
Visit an interactive diagram of the wastewater treatment process.


Did you know?

Wastewater collected
from your house
is not only from the toilets,
but also from showers, dishwashers, sinks, and your clothes washer.


Big Gulch Wastewater Treatment Facility

Street Address:
9417 62nd Pl W
Mukilteo, WA

Phone Number: 425-355-6637
Fax Number: 425-355-4263

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