Usually there is also a clause titled severability, staing if anything in the document is found to be unenforcable then the remainder of the document stays and the offending clause is stricken.
If your rental situation is covered by the WA Residential Landlord-Tenant Act, you can review the RLTA, specifically RCW 59.18.230 (Waiver of chapter provisions prohibited — Provisions prohibited from rental agreement — Distress for rent abolished — Detention of personal property for rent — Remedies). The statutes are at http://apps.leg.wa.gov/rcw/default.aspx?cite=59.18 .
Your lease would need to be reviewed to see whether its provisions are in violation of the RLTA.
Moreover, RCW 59.18.230 provides: "(3) A provision prohibited by subsection (2) of this section included in a rental agreement is unenforceable. If a landlord deliberately uses a rental agreement containing provisions known by him to be prohibited, the tenant may recover actual damages sustained by him and reasonable attorney's fees."
The RLTA does not make the entire contract unenforceable.
You should consult with your attorney to see what legal options you have.