Short definition

Heavy metals in drinking water include lead, copper, arsenic, mercury, cadmium, and chromium-6. Each has a different source pattern, regulatory limit, and treatment. In Washington, the most common concerns are lead from pre-1986 plumbing, arsenic in eastern WA private wells, and copper from corrosive water in older copper systems.

What it is

Heavy metals enter potable water from four main routes:

  1. Source water — natural geology (arsenic in eastern WA groundwater) or upstream contamination
  2. Treatment chemicals — historically a path for contamination; modern practice is well-controlled
  3. Distribution mains — lead service lines (rare in WA but documented in some old Tacoma neighborhoods) or galvanized lines accumulating lead from upstream sources
  4. Premises plumbing — pre-1986 lead solder in copper joints, pre-1989 brass fittings with up to 8% lead content, and the home’s own internal pipework

Each metal has its own EPA regulatory limit. Lead has an action level of 15 ppb (15 parts per billion), copper 1.3 ppm, arsenic 10 ppb. The federal Reduction of Lead in Drinking Water Act (2014) defines “lead-free” plumbing as ≤0.25% lead by weight; brass fittings post-2014 carry an NSF 372 “Lead-Free” marking.

In 2024, EPA finalized the Lead and Copper Rule Improvements (LCRI), setting a maximum contaminant level goal for lead at zero and requiring service-line inventory and replacement at all public water systems. Implementation in Washington is being rolled out by individual utilities through the late 2020s.

Why it matters to a homeowner

Three reasons heavy metals are a load-bearing topic for WA homeowners:

Pre-1986 homes are common in the metro. Seattle, Tacoma, Bellevue, Everett, and Spokane all have substantial housing stock from before lead solder was banned. Soft, slightly acidic Cedar/Tolt water (Seattle’s source) is naturally aggressive on lead. SPU adds corrosion-control chemistry that limits leaching, but a first-flush sample after stagnation can still show elevated lead. Run cold water 30–60 seconds before drinking; never use hot tap water for cooking or infant formula.

Eastern WA private wells often show arsenic. The geology around the Yakima Valley, Columbia Basin, and parts of the Okanogan can put naturally-occurring arsenic into well water. EPA’s MCL is 10 ppb. Test before assuming a well is safe; treat with point-of-use RO or whole-house anion exchange if elevated.

Most consumer filters don’t remove what they imply. Reading certified-claims lists matters. NSF/ANSI 53 covers lead, cadmium, chromium, mercury. NSF/ANSI 58 (RO) covers a broader spectrum. Marketing copy (“removes contaminants”) is not a substitute for a printed claim list.

When you’ll encounter this term

  • Pre-1986 home in Seattle: SPU’s corrosion control limits lead, but vulnerable household members may want a point-of-use filter for cooking and drinking
  • Buying rural property in eastern WA: include arsenic in the water-test panel
  • Pregnant household or household with infants in any older plumbing: switch to bottled or POU-filtered water for drinking and formula until a current test is in hand
  • Lead service line replacement program: the utility may pay for the public-side; the homeowner pays the private-side

Common failure modes (sources of heavy metals at home)

  • Pre-1986 lead solder in copper plumbing — leaches lead, especially with soft acidic water
  • Pre-1989 brass fittings with up to 8% lead content
  • Lead service line (rare in WA but documented in some old Tacoma neighborhoods) — full replacement is the only fix
  • Galvanized service line downstream of an old lead gooseneck — galvanized accumulates lead even after upstream replacement
  • Arsenic in groundwater — natural geological source; eastern WA wells particularly
  • Cadmium in galvanized pipe corrosion — older galvanized systems
  • Hot water service higher in dissolved metals than cold — don’t use hot tap for cooking or baby formula
  • Stagnant water — first flush after long absence carries higher metal load (run cold tap 30–60 s before drinking)

Cost data

ItemCost
Comprehensive home water test (heavy metals panel)$150–$400 mail-in lab
Point-of-use RO under-sink system$200–$500 hardware + $80–$150 install
Whole-house arsenic-removal (anion exchange)$1,500–$3,500
Lead service line replacement (when found)$3,000–$10,000+ depending on length and jurisdiction; some utilities subsidize the public-side portion

Common variants and disambiguation

  • Lead vs. copper. Both regulated together (Lead and Copper Rule) but distinct chemistry and risk. Copper is taste/aesthetic at moderate levels, GI issues at high levels. Lead is neurotoxic with no safe level — federal MCL goal is zero.
  • Arsenic forms (As III vs. As V). Treatment differs; pre-oxidation may be required for trivalent arsenic.
  • Heavy-metal-removal filter labels. NSF/ANSI 53 (Pb, Cd, Cr, Hg) vs. NSF/ANSI 58 (RO, broader spectrum). Read the certified-claims list, not the marketing copy.

Washington note

WA Group A water systems comply with the EPA Lead and Copper Rule via WAC 246-290. The 2024 EPA Lead and Copper Rule Improvements (LCRI) set lead’s MCL goal at zero and require service-line replacement for all systems — implementation is rolling out by individual WA utilities. Verify your local utility’s lead service line inventory status if you live in a pre-1950 neighborhood.

WA Department of Health enforces the federal arsenic MCL of 10 ppb on Group A and B systems. For private wells, no federal MCL enforcement applies, but DOH recommends arsenic testing at well-water purchase and at new construction. Rural eastern WA wells in geological arsenic zones should be tested at minimum every 3–5 years.

If you’re in Seattle and concerned about lead from pre-1986 premises plumbing: SPU’s corrosion-control program limits leaching, but a cold-tap first-flush sample is the most informative test. Test for lead at the kitchen tap if you have any concern; the cost is modest, the answer is permanent for the test conditions.