Your well water can be crystal clear, taste great, and still carry arsenic at levels the EPA says aren’t safe to drink. No smell. No color. No warning. That’s what makes arsenic in well water different from almost every other well problem we deal with in North Central Washington.
Here’s the good news. Testing is cheap, the science is settled, and treatment works. If your test comes back high, you have several proven options, and most of them cost less than people expect. In this guide we’ll cover why arsenic shows up in wells around Wenatchee, Cashmere, and Chelan, how to test the right way, what the numbers actually mean, and which treatment systems remove arsenic for real. We’ll also give you honest cost ranges, because guessing is no way to plan.
If you’d rather skip the homework and just get your water checked, request a free estimate and we’ll point you to the right lab test and walk you through the results.
Why Arsenic in Well Water Is a North Central Washington Problem
Arsenic isn’t something a factory dumped in your well. Around here it comes from two main sources, and both are baked into our local history and geology.
Natural arsenic in the rock
Arsenic occurs naturally in the volcanic and sedimentary rock that groundwater moves through in Chelan, Douglas, and Grant counties. As water sits in fractured bedrock, it slowly dissolves trace minerals, arsenic included. Deeper wells with older, slower-moving water often pick up more of it. The USGS has mapped arsenic in groundwater across the country, and parts of central Washington show up as moderate to elevated risk zones.
Legacy orchard pesticides
This one is specific to our valley. From roughly 1905 to 1947, lead arsenate was the standard pesticide sprayed on apple and pear orchards from Wenatchee to Cashmere to Chelan. Decades of spraying left arsenic and lead in the top layers of orchard soil. The Washington Department of Ecology has tracked these legacy pesticide areas for years.
Most of that contamination stays in shallow soil, so a properly sealed well drawing from deep bedrock is usually protected. But shallow wells, old hand-dug wells, and wells with cracked casings or bad surface seals on former orchard land are a different story. If your property grew fruit before 1950, and around here a lot of properties did, you should test.
It doesn’t announce itself
Arsenic has no taste, no odor, and no color at the levels found in wells. Your water can look perfect. Unlike iron in well water that stains your fixtures orange, or rotten egg smells that hit you at the tap, arsenic gives you nothing to notice. Testing is the only way to know.
What Counts as a Safe Level
The EPA’s maximum contaminant level for arsenic in public drinking water is 10 parts per billion, written as 10 ppb or 0.010 mg/L. Private wells aren’t regulated, so nobody enforces that number on your well. It’s still the right benchmark to use.
A few things worth knowing about that number:
- 10 ppb is a regulatory limit, not a bright line between safe and dangerous. The EPA set it balancing health risk against treatment cost. Some health agencies suggest aiming lower, especially for infants and pregnant women.
- Long-term exposure is the concern. Drinking arsenic at low levels for years is linked to increased risk of skin, bladder, and lung cancers, plus cardiovascular and skin effects. One glass of 15 ppb water won’t hurt you. Twenty years of it is the problem.
- Results between 5 and 10 ppb deserve a retest. Arsenic levels can shift with the seasons and with how hard the aquifer is being pumped. One sample is a snapshot, not the whole movie.
The Washington State Department of Health recommends every private well owner test for arsenic at least once, and retest if anything about the well changes.
Marcus and Jenna found this out the practical way. They were buying a 1970s house on two acres outside Leavenworth last spring, on land that was orchard a lifetime ago. Their lender didn’t require an arsenic test, but their inspector suggested one. It came back at 14 ppb. They negotiated a $2,000 credit at closing and installed treatment for less than that. Without the test, they’d have been drinking that water for years without a clue. If you’re in that situation, our guide to well inspections when buying a home covers what else to check.
How to Test Your Well Water for Arsenic
Skip the strip kits from the hardware store for this one. Arsenic at 5 to 20 ppb needs a certified lab, and the test is cheaper than most people think.
Here’s how to do it right:
- Use a Washington-accredited lab. There are certified drinking water labs serving the Wenatchee Valley, Quincy, and Moses Lake. A standard arsenic test runs $25 to $50. Many labs sell a private well panel for $100 to $200 that bundles arsenic with bacteria, nitrates, lead, and other basics.
- Sample from a cold tap before any treatment equipment. You want to know what’s in the well, not what your fridge filter is catching.
- Follow the bottle instructions exactly. Arsenic samples are usually preserved with acid in the bottle. Don’t rinse it out.
- Test more than once if you’re near the limit. Sample in late summer when the aquifer is low and again in spring. Levels can swing several ppb between seasons.
When should you test? At minimum: when you buy a home with a well, after any well repair or deepening, and every 3 to 5 years even if past results were clean. Annually if you’ve ever had a detection above 5 ppb. We walk through the full testing playbook, including bacteria and nitrates, in our guide to well water testing in Wenatchee.
Not sure which test to order or how to read the report once it lands in your inbox? Call us at (509) 224-3484 and we’ll talk you through it. No charge for the conversation.
Treatment Options That Actually Remove Arsenic
If your test comes back over 10 ppb, don’t panic and don’t buy the first filter you see online. A few technologies remove arsenic reliably. Several popular ones don’t touch it.
What works
Reverse osmosis (RO). A point-of-use RO unit under the kitchen sink is the most common fix for homes in our area. It forces water through a membrane that rejects arsenic along with nitrates, lead, and most dissolved solids. Good units remove 90 to 95 percent of arsenic. You treat only the water you drink and cook with, which keeps costs down.
Adsorptive media filters. These use iron-oxide based media that grabs arsenic as water passes through. Available as under-sink cartridges or whole-house tanks. Low maintenance, no wastewater, but the media is a consumable you replace when it’s exhausted.
Anion exchange. A whole-house system that swaps arsenic for chloride, similar to how a softener swaps hardness. It works well on arsenic 5 (the oxidized form) but can be thrown off by sulfate in the water, so it needs a proper water analysis first.
One wrinkle: arsenic comes in two forms, arsenic 3 and arsenic 5. RO and most media handle arsenic 5 well but struggle with arsenic 3, which sometimes needs an oxidation step (often simple chlorination) ahead of the filter. This is exactly why a $40 speciation test before buying equipment can save you from a $1,500 mistake.
What doesn’t work
- Boiling. Worse than useless. Boiling evaporates water and concentrates the arsenic left behind.
- Standard carbon filters. Pitcher filters and basic fridge filters are built for taste and chlorine, not arsenic.
- Water softeners. They remove hardness, not arsenic.
- UV systems. UV treatment kills bacteria and viruses. It does nothing to dissolved metals.
For a broader look at matching equipment to your water chemistry, see our overview of well water filtration systems.
What Arsenic Treatment Costs in the Wenatchee Valley
Real numbers, installed, for our service area:
| Treatment option | Installed cost | Annual upkeep | Best for |
|---|---|---|---|
| Under-sink RO system | $400 - $1,500 | $100 - $200 (filters, membrane) | Most homes; drinking and cooking water |
| Under-sink adsorptive cartridge | $300 - $800 | $150 - $300 (media cartridges) | Moderate arsenic, simple install |
| Whole-house adsorptive media tank | $2,000 - $5,000 | $300 - $800 (media changeouts) | High arsenic, big households |
| Anion exchange (whole house) | $1,800 - $4,000 | $150 - $400 (salt, resin) | Arsenic 5 with low sulfate |
| Pre-oxidation add-on (if arsenic 3) | $500 - $1,500 | $50 - $150 | Wells with reduced groundwater |
A note on whole-house versus point-of-use. Arsenic risk comes almost entirely from drinking and cooking. Showering and laundry in arsenic water is not a meaningful exposure at typical well levels. That’s why most families do fine with an under-sink RO at the kitchen tap for under $1,500, instead of treating every gallon that runs through the house.
Rita’s place in Cashmere is a good example. Her property is old orchard ground, and her shallow 1960s well tested at 18 ppb. She’d been quoted $6,800 for a whole-house system by an out-of-town outfit. We ran a speciation test, found mostly arsenic 5, and installed an under-sink RO for $1,100 with about $150 a year in filters. Her treated water now tests below 2 ppb. Same protection, a fifth of the price.
And in Quincy, Dale learned the maintenance lesson. He installed an RO unit himself in 2019, then never changed the membrane. When he finally retested in 2025, his “treated” water was at 11 ppb because the membrane was shot. Treatment isn’t install-and-forget. Test the treated water once a year, every year. It’s a $30 check on a system protecting your family.
While we’re at your place for a water issue, it’s worth having the whole system looked at. An aging pump or a failing pressure tank often gets caught during the same visit. If your water has also been sputtering or losing pressure, our well pump repair team in Wenatchee can diagnose both in one trip, and we handle well service throughout Cashmere and the rest of the valley.
What to Do This Week
Keep it simple:
- Order a certified lab arsenic test, or a full well panel if you’ve never tested. Budget $25 to $200.
- Sample correctly, from a cold untreated tap.
- Under 5 ppb: relax, retest in 3 to 5 years.
- Between 5 and 10 ppb: retest in a different season and consider treatment if you have kids or are expecting.
- Over 10 ppb: get a speciation test, then install the right treatment. Use bottled water for drinking, cooking, and baby formula in the meantime.
- After install: test the treated water annually and keep up with filter changes.
One thing not to do: don’t ignore a high result because the water tastes fine. It always tastes fine. That’s the whole problem with arsenic.
If you want a second set of eyes on a lab report, or a straight quote on treatment, reach out for a free estimate. We’re licensed and insured in Washington, we work on wells from Leavenworth to Moses Lake every week, and we’ll tell you honestly if a $400 fix will do the job.
Frequently Asked Questions
Is it safe to shower in well water with arsenic?
Yes, at the levels typically found in private wells. Arsenic isn’t absorbed through the skin in meaningful amounts, and it doesn’t vaporize in a hot shower the way some contaminants do. The exposure that matters is drinking and cooking, which is why point-of-use treatment at the kitchen sink covers most of the risk.
How often should I test my well for arsenic?
Test at least once no matter what, since you can’t taste or smell it. If results are under 5 ppb, retest every 3 to 5 years or after any well work. If you’ve ever had a result above 5 ppb, or you have treatment equipment installed, test annually. Always test when buying a home with a well.
Will a water softener or fridge filter remove arsenic?
No. Softeners exchange hardness minerals and don’t capture arsenic, and standard carbon filters in fridges and pitchers are designed for chlorine and taste. You need reverse osmosis, adsorptive media designed for arsenic, or anion exchange. Verify any system you buy is certified to NSF/ANSI 53 or 58 for arsenic reduction.
My neighbor’s well tested clean. Does that mean mine is fine?
Unfortunately not. Two wells 300 feet apart can draw from different depths and different fractures in the rock, and arsenic levels can vary a lot between them. Legacy orchard contamination also varies parcel by parcel. The only way to know your water is to test your well.