Wash. Rev. Code § 61.10.040
On or after July 1, 1998, no borrower entering into a residential mortgage transaction in which the principal amount of the loan is less than eighty percent of the fair market value of the property shall be required to obtain mortgage insurance. Fair market value for a purchase money loan is the lesser of the sales price or the appraised value. This section shall not apply to residential mortgage transactions in an amount in excess of the maximum limits established by institutional third parties where the borrower and the lender have agreed in writing to mortgage insurance.
A lender or person servicing a residential mortgage transaction who complies with federal requirements, as now or hereafter enacted, governing the requirement of obtaining mortgage insurance shall be deemed in compliance with this section.
RCW 61.10.040