The main tax advantage there would only apply if you lived in Washington and drove to Oregon for significant purchases (cars, electronics, potentially groceries, whatever makes up the bulk of your spending). This is because Oregon doesn’t have sales tax and Washington doesn’t have income tax (Oregon has some of the highest income taxes in the nation, depending on your tax bracket, 4.75-9.9% per nerdwallet. Property taxes are roughly the same at the state level.
If you’re thinking about moving because you have free agency and want to get the most bang for your buck, considering tax burdens of places you’re looking at should definitely be a data point, since that can make a big financial difference depending on your lifestyle, spending habits, and future income.
I don’t know how common this is, but where I live (PNW), our city water has more than one source, and based on a number of factors, the water running to our house may have its source changed for short periods of time. Have you talked to any of your neighbors to see if they’ve experienced something similar? You might try reaching out to the city water department and see if they have any idea what it might be as well, they may even have free (or cheap) water testing you can do on water from your house.
Unfortunately I don’t have any real answers for whether your water is safe to drink or not, but hopefully something here will be of some help to you.