Aftermarket Exhaust in Washington
Replacing the exhaust system is legal in Washington, but a muffler in good working order is required and cutouts or bypasses are prohibited. Modifications that make the exhaust louder than the originally installed muffler are specifically prohibited.
Verified against primary sources · August 2026
What the law says
Replacing the exhaust system is legal in Washington, but a muffler in good working order is required and cutouts or bypasses are prohibited. Modifications that make the exhaust louder than the originally installed muffler are specifically prohibited. Removing the catalytic converter is prohibited by federal law (Clean Air Act § 203) regardless of state rules. Ringelmann smoke standards apply separately. Washington has had no emissions program since January 1, 2020.
Specific Limits
- Cutouts
- prohibited
- Muffler required
- Yes
- Louder than stock
- prohibited by statute
- Catalytic converter
- removal prohibited by federal law
Frequently Asked Questions
Are aftermarket exhaust legal in Washington?
What are the exact aftermarket exhaust limits in Washington?
Street-legal aftermarket exhaust picks
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