Testing your well water: what, when and what to do next

Nobody tests a private well for you. Washington DOH and Ecology both say private well owners are responsible for their own water quality. Testing is cheap compared with the problems it catches, and a few contaminants can make people sick after a single glass. Here is what Washington’s agencies recommend, how to sample, and what to do if a result comes back bad.

What to test, and how often

• Coliform and nitrate every year. DOH recommends testing every year for both, because they can “rapidly affect a person’s health”, possibly after a single drink (Ecology).
• Arsenic twice. DOH’s testing page suggests testing for arsenic at least twice while you own the well, “once in summer and again in winter”. Its arsenic page puts it as once in late summer and once in early spring. Either way, the point is to catch seasonal changes.
• Local extras. DOH’s guidance to local governments also recommends initial testing for iron and manganese, for chloride near salt water, and for uranium in northeast Washington. NGWA’s annual checkup adds tests for local contaminants of concern, commonly iron, manganese, hardness and sulfides.
• Test after problems too. Ecology suggests testing after flooding in your area, and NGWA says cloudy, discolored or foul-smelling water “should be tested immediately”. Test after any work that opens the well, once the chlorine has flushed out (see below).

Some counties have their own rules. Clark County requires coliform, arsenic and nitrate tests on new and replacement wells. Spokane Regional Health District recommends that private well owners in Spokane County test for uranium, arsenic and PFAS.

Use an Ecology-accredited lab

Ecology accredits the labs that test drinking water. Use its lab search to filter by test, by county and by the drinking water matrix, and to find labs that accept samples from the public. Ecology also publishes a list of accredited drinking water labs by county. Our testing directory lists labs with their Ecology accreditation numbers, including those that offer coliform, nitrate, arsenic and metals and PFAS tests.

Cost (indicative only). DOH’s testing page quotes 2010 prices of about $25 to $50 per test. That figure is old, so ask the lab for current prices.

Sampling tips

• Get the kit and instructions from the lab. DOH says lab staff can explain how to collect samples. Follow their instructions exactly, and check the lab’s drop-off days and hours before you sample.
• Sample when the well isn’t chlorinated. If the well has just been chlorinated or worked on, wait. Tacoma-Pierce County Health Department (TPCHD) says repeat samples shouldn’t be taken until there is no chlorine taste or odor, which can take two to three days.
• Time your arsenic tests by season: late summer, then early spring or winter.
• Keep every report. Year-to-year results show trends, and buyers or lenders may ask for them when you sell (see buying a home with a well).

Reading your results

Coliform bacteria. TPCHD says a “satisfactory” result is what you want. An “unsatisfactory” result may mean disease-causing bacteria are in your water. See the next section for what to do.

Nitrate. DOH’s standard is 10 mg/L (as nitrogen).

• Above 10 mg/L: DOH says not to drink the water if you are pregnant or trying to become pregnant. Don’t give it to babies under 12 months; it can cause “blue baby syndrome” (methemoglobinemia). Use bottled water for food, drinks and formula.
• 5 mg/L or more: DOH suggests re-sampling in six months.
• Don’t boil it. DOH says boiling kills bacteria but can raise nitrate levels, because nitrate stays behind as the water evaporates.
• Where it comes from: fertilizers, manure, dairy lagoons and septic systems. Chelan-Douglas Health District requires a Notice to Title when a new home’s well tests at 10 ppm or more.

Arsenic. DOH recommends no more than 10 ppb in water for drinking and cooking. It says levels from 10 ppb up to 33,000 ppb have been found in some Washington wells. Common taste-and-odor filters don’t remove arsenic. Reverse osmosis, distillation or special filter media can; DOH recommends NSF-certified equipment and retesting after it is installed and maintained. A new well at a different depth or location “may or may not” fix the problem. See arsenic treatment and reverse osmosis providers.

After a positive bacteria test

1. Look for a way in. NGWA lists damaged casing, a deteriorated cap and signs of flooding or surface water getting in as warning signs, and says a damaged or loose cap should be checked by a professional.
2. Disinfect the well. TPCHD’s procedure (below) is a one-time shock chlorination for wells that have tested positive. Chelan-Douglas Health District likewise says to disinfect and resample after a positive result.
3. Retest once the chlorine is gone. NGWA’s disinfection practice recommends a coliform sample after the chlorine is flushed, and a second sample 24 hours later to confirm.
4. If it comes back positive again, TPCHD says the water system may need a more thorough assessment. NGWA says a well that doesn’t respond to treatment may need repair or replacement. A well service company can inspect the wellhead, seal and casing, and some offer shock chlorination.

Ask your local health department what to drink in the meantime.

Shock chlorination, step by step

This is TPCHD’s procedure for drilled wells. TPCHD recommends having a water professional open the well. It says to call the health department instead if you have a hand-dug well, sand point or spring, which need other procedures.

1. Do it in the evening. Turn off the electricity to the pump.
2. Remove the well cap or the access-port plug.
3. Work out how much bleach you need from the casing size and well depth (see the table). Use plain household bleach (about 8% chlorine). Avoid concentrated or “ultra” products, which over-chlorinate, and bleach with additives or perfumes.
4. Mix the bleach with water, then pour it into the well through a funnel.
5. Leave the pump off for two to three hours so the chlorine has time to work.
6. Turn the pump back on. Open every indoor faucet in every home on the well until you smell bleach, then close them and let the system sit overnight.
7. In the morning, or after at least 8 hours, run the outside faucets until you can no longer smell chlorine.
8. Retest only once the chlorine is completely gone (no taste or odor). That can take two to three days.

TPCHD’s bleach amounts for a 6-inch casing, a common home well size:

TPCHD’s sheet also gives amounts for 8-, 10- and 12-inch casings.

PFAS

PFAS (per- and polyfluoroalkyl substances) are chemicals released from consumer and industrial products; Ecology says firefighting foam is a key suspected source of PFAS in Washington drinking water. DOH says private well owners “are not required to test for PFAS chemicals”. It suggests checking whether PFAS has been found in your area and asking your local health department whether it is sampling near you.

Ecology lists areas where it knows PFAS has contaminated groundwater:

• Bailer Hill (San Juan Island);
• the Joint Base Lewis-McChord area;
• the lower Issaquah Valley (King County);
• Naval Base Kitsap (Bangor);
• the U.S. Army Yakima Training Center;
• the West Plains (Spokane County);
• Whidbey Island Naval Air Station.

If you’re in or near one of those areas, test.

• Use an Ecology-accredited lab that is accredited for PFAS in drinking water.
• Ask which EPA method the lab uses. Ecology says methods 533 and 537.1 both detect the PFAS that have a drinking water standard.
• Compare results with the lower limit. DOH says to act if levels exceed EPA’s maximum contaminant levels or Washington’s State Action Levels, using “whichever number is lowest”.
• Treatment: DOH says to use a filter certified to reduce PFAS by an independent third party such as NSF or the Water Quality Association, either at one tap or for the whole house. “Water softeners do not work to remove PFAS.”

Questions to ask a lab

1. Are you accredited by Ecology for this test in drinking water?
2. Can I pick up a sample kit, and what are your drop-off days and hours for bacteria samples?
3. Which method do you use for PFAS?
4. What does each test cost, and how soon will I get results?
5. Will the report show the drinking water standard next to my result?

Red flags

• An in-home test by someone selling treatment equipment offered in place of a report from an accredited lab.
• Treatment sold before the water has been tested, or for a contaminant you haven’t tested for.
• An ordinary taste-and-odor filter sold to remove arsenic.
• A water softener sold to remove PFAS.
• A bacteria sample taken while chlorine is still in the system.
• A well that tests positive for bacteria again and again but is only ever chlorinated, never inspected.