Private and shared wells on the peninsulas

Private well owners test their own water; the Department of Health recommends coliform and nitrate tests every year, Ecology regulates well construction, and the county health office covers local well rules.

Revised November 4, 2026

How often to test, and for what

The state and the Pierce County department publish different nitrate schedules, so here are both, each under its own name.

• Department of Health. It recommends testing every year for coliform bacteria and nitrate. At nitrate of 5 mg/L or higher, it says you may want to re-test in six months.
• Tacoma-Pierce County Health Department. For a single-family well, its page gives bacteria annually and nitrate at three-year intervals.

Yearly is the more cautious of the two. The Department of Health also suggests arsenic tests at least twice while you own the well, one in summer and one in winter. A 2019 state leaflet adds three triggers: a change in taste, color or smell, flooding, and replacing any part of the well system.

One warning matters most for families: the department says not to boil well water with high nitrate. Ask your health office what to do instead.

Where to send a sample

Use a certified lab, and call first. A state nitrate publication says to search Ecology's list of certified labs, then phone to make sure the lab is accredited for nitrate in drinking water. The department's testing page says lab staff can tell you how to collect samples. The Department of Health also posts a March 2026 lab list.

For a rough first look, before the certified lab test the state describes and never in place of it, one screening option is a hardness, iron and pH test kit. Quality Water Treatment is run by the same team as this site.

Who regulates what

The answer changes with the question and with how many homes share the well.

• Construction. Ecology regulates it. It says a notice of intent must go in 72 hours before drilling, typically handled by the licensed driller. Its State Well Report Viewer shows construction records for individual wells.
• Larger use. Ecology says that above 5,000 gallons per day, or irrigating more than half an acre, you need to apply for a water right before drilling.
• Rules cited locally. The Pierce County department says private wells fall under WAC 173-160, large public systems under WAC 246-290, and that Chapter 3 of its Environmental Health Code covers wells and water systems.
• Shared wells. A small shared system can be a Group B public water system with duties of its own. Ask your health office which class yours falls in. For most residential Group B systems, the state says irrigation, chemigation and farm animals are the likeliest contamination risks, which is the ground covered in backflow and irrigation rules.

Not sure whether you have a well or a supplier? Finding your water supplier settles that first, and selling a house on septic covers the water papers at sale time.

Is seawater a risk here?

For Kitsap there is a general warning; for Pierce County we found no official statement. USGS says Kitsap Peninsula groundwater is limited, largely because seawater bounds it, and that the potential for water-level declines and seawater intrusion rises as use rises.

Other findings are narrower. A 2018 Bainbridge Island study, outside this atlas's area, found elevated chloride localized to one well and not a regional problem. A 1980 USGS report found no widespread seawater contamination in its Kitsap study area, though some local areas exceeded 25 mg/L chloride, and it is 46 years old.

For the Key Peninsula, the Gig Harbor Peninsula and Fox Island, we could not confirm any current chloride data or official statement either way. USGS has a 1981 report on the Gig Harbor peninsula, too old to settle today's question. If you live near the shore and want an answer, ask the health office about adding chloride to your lab test.

Parts, stains and hard water

A replaced part is a testing trigger, as above. Iron, hardness and staining are questions for the page on iron and hard water, and lab results should come before any treatment.

If your well or pump contractor specifies a replacement pressure tank, sizes and types are listed under well tanks. The same team runs PlumbingSupplyAndMore and this site.

Do not climb into a well pit or any pit: we advise leaving that to a licensed well or pump contractor. Stick to checking a breaker or switch, and leave any other electrical work on a pump to a licensed professional. Call 811 before digging near a well line or anywhere else. If unsure, call a licensed plumber.