1. The best place to start in Kelso, WA is the Cowlitz County Health Department at http://www.co.cowlitz.wa.us/health/environmentalhealth/water . They can advise you concerning the local ground water and what tests they recommend. They may tell you, for example, that the public water is tested every 3 years for atrezine and they can recommend specific tests for the area.
2. You should also consult your lender to find out their requirements. Some lenders only require a test for colliform. However, FHA requires coliform, arsenic, and nitrate testing.
3. And, you personally, may want to consult a lab such as Columbia Analytical Services to discuss the entire range of tests possible for drinking water. Their website is: http://www.caslab.com/Drinking-Water-Testing/ .
Columbia Analytical Services is one of several local labs you will find on the Cowlitz County Health Department website. They have a 3 week turnaround time and a 50% surcharge for faster service. They charge a $150 minimum. A panel of tests for a large number of contaminants is $225.
Water quality is a critical factor to maintaining your health. Consulting your local health department, your lender, and a local lab will give you important information. If the ground water in your area is good, many people enjoy well water.
Your Realtor will help you with well water and other inspections for your new home.