If a rental agreement states the landlord has 30 days to refund the deposit, does this clause supercede the 14-day requirement?

The statute trumps your rental agreement. The statute has an express provision about lease agreements that impose greater burdens on tenants than what is allowed in WA. If you were to take them to small claims, the Court will find that the statute controls not the private agreement. See RCW 59 18 240, especially (2) a.

This happens when landlords save money by downloading a rental agreement off the internet rather than consulting with a local real property attorney. Oh, well.

Hope this helps. Elizabeth Powell