On October 14, 2009, The Washington State Board of Health held a public hearing to adopt a much needed on-site sewage system tanks rule. The rule "Draft 246-272C WAC On-site Sewage System Tanks" is currently being used in the design and approval of new systems in the state, and should become official by the end of 2009. Basically, the rule sets guidelines for septic tanks being sold in the state and provides a list of approved manufacturers. Homeowners and contractors will purchase tanks from the approved list, have the tank installed, and then tested to ensure tank is water tight. This decreases the possibility of a leaky tank overloading the drain field and, thus causing release of contaminants prior to proper filtration by the soil contents.
See the following link for On-site Sewage System Tanks
For additional information contact:
Office of Shellfish and Water Protection
Mailing address: PO Box 47824
Olympia, WA 98504-7824
Physical address: 111 E Israel Road
Washington also attempts to make use of greywater management. Greywater is the water from your home other than the toilets, like sinks, washing machines, etc.. Managing greywater by means other than the septic system is an excellent economical use of this discharge by watering plants, lawns, etc....
See the Greywater Fact Sheet issued by the Washington State Department of Health.