Declares that manufacturers of proprietary treatment products that use soil-based denitrification processes in the drain fields of on-site sewage disposal systems are exempted from registering such proprietary treatment products with the department only if the following conditions are met: (1) The proprietary treatment product must conform to the universal plumbing code;

(2) Any biological component used in the proprietary treatment product must meet the conditions of RCW 70.118.060 relating to additive regulation;

(3) For purposes of product testing, sampling for total nitrogen discharge to the soil is drawn using a soil vacuum lysimeter or by other means approved by the department;

(4) The results of product testing in the soil surrounding the drain field test sites must be at or below ten parts per million of total nitrogen;

(5) Testing data is submitted to the department for review and approval or denial; and

(6) The proprietary treatment product is installed into a septic system with a preexisting on-site permit.