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Plumbing can be difficult. Public Health - Seattle & King County recommends you hire a professional plumber. If you choose to do your own plumbing, please adhere closely to the following instructions.

When a permit is required

Whenever you are going to install, relocate or change a plumbing or gas piping system, Seattle and King County codes require that you obtain a permit. Public Health — Seattle & King County has jurisdiction in Seattle and unincorporated King County.

The permit issued to a homeowner is an authorization for the homeowner to do the plumbing. (See RCW 18.106.150) If you are being authorized by the property owner to apply for the plumbing permit, your signature on the permit application signifies that you have such authorization from the owner of the property. If a professional plumber is contracted with, they must be a registered contractor per Chapter 18.27 RCW.