well-water-test-decoder

Use when a private well water test comes back with numbers and no explanation, before buying water treatment equipment, or diagnosing taste/stain/odor symptoms — parameter-by-parameter decode of hardness/iron/pH/nitrates/TDS/coliform against EPA secondary and MCL standards, symptom fingerprinting (blue-green stain = corrosive water, rotten-egg = SRB), treatment-selector logic that prices the right unit, and the oversell-guard against whole-house RO for normal problems.

Overview

~43 million Americans drink private well water, and EPA standards don't apply to private wells — testing is the homeowner's job, and treatment is where a $30 lab report becomes a $3,000 sales call. The classic move: a free "water test" from a treatment company (strips that read everything bad), then a pitch for a whole-house system priced against fear. The information gap is the product being sold.

This skill decodes a lab report line by line: each parameter against its EPA MCL (health) and secondary standard (aesthetic), each with what-it-means and fix-if-over. It fingerprints symptoms (stains, odors, taste, appliance scale) to parameters before you test, generates the right test panel to order (county/state labs, $20–$150; skip the free pitches), and runs treatment-selector logic with honest price bands — including the oversell-guard: whole-house RO is almost never the answer, and a softener sold for iron removal clogs when iron > 5 ppm needs an oxidizing filter instead.

When to Use

• Lab report back; numbers in mg/L or ppm; no idea what's actionable
• Symptoms: stains (blue-green, brown, black), rotten-egg smell, metallic taste, scale, recurring gastro illness
• Buying/building on a property with a well (test BEFORE closing — it's a negotiation item)
• A treatment salesman's proposal to sanity-check
• Annual/5-year retest scheduling (coliform annually; nitrate + arsenic every 3–5 yr; full panel at sale or after flood/work on the well)

Don't use for: municipal water reports (CCR — different standards, utility-owned), wastewater, or pools. Coliform-positive: this skill interprets and routes to shock-chlorination/pro-lab; it does not replace county health dept guidance.

Quick Start

bash

# Decode every parameter on a lab report
python3 scripts/wellwater.py decode --hardness 142 --iron 3.2 --manganese 0.4 \
    --ph 6.4 --nitrate 4.1 --tds 380 --coliform absent --arsenic 3

# Symptom-first: what should I test for?
python3 scripts/wellwater.py symptoms --stains blue-green --corrosion pipes

# Treatment sanity-check: sales quote for softener + RO under sink
python3 scripts/wellwater.py treat --hardness 142 --iron 3.2 --ph 6.4

# What test panel to order (new property)
python3 scripts/wellwater.py panel --context new-property

The Standards (what decode checks against)

Parameter	EPA MCL / action	Secondary (aesthetic)	Over-limit meaning
Total coliform	0 present	—	surface intrusion / well defect — fix the well, not just the water
E. coli	0	—	fecal contamination — health emergency, do not drink
Nitrate (as N)	10 mg/L	—	infant methemoglobinemia; septic/farm proximity
Arsenic	10 µg/L	—	chronic (cancer); common in New England/Midwest aquifers
Lead	15 µg/L (AL)	—	usually plumbing/corrosive water, not the well
Iron	—	0.3 mg/L	red-brown stains, metallic taste
Manganese	0.12 (health adv.)	0.05 mg/L	black stains; neuro (children) at high levels
Hardness	—	>120 mg/L "hard"	scale, soap waste; no health harm
pH	—	6.5–8.5	<6.5 corrosive (leaches lead/copper); >8.5 scaling + chlorine taste
TDS	—	500 mg/L	brackish taste; RO point-of-use if extreme
Sulfate	—	250 mg/L	laxative effect at high dose
Chloride	—	250 mg/L	road salt / sea proximity

Symptom Fingerprints

Symptom	Prime suspects (in order)	First test
Blue-green stains, pinhole leaks	pH < 6.5 / low alkalinity corrosion	pH + alkalinity + lead/copper
Brown/red stains, rusty water	Iron > 0.3 (ferrous clears after standing)	iron + manganese + pH
Black stains on fixtures	Manganese (or Mn+Fe sulfur bacteria)	manganese + iron bacteria (slider)
Rotten-egg smell (hot only)	Sulfate-reducing bacteria in water heater (anode)	replace magnesium anode w/ aluminum-zinc; no test needed
Rotten-egg (cold too)	H₂S gas / SRB in well	H₂S test + shock chlorination
Musty/earthry	Iron bacteria or surface organic	check well cap, coliform
White scale, kettles	Hardness > 120 mg/L	hardness + TDS
Soap won't lather	Hardness	hardness
Recurring GI illness in household	Coliform / E. coli / nitrate	bacteria + nitrate — lab, not strips
Salty taste	Chloride/TDS (road salt, sea)	chloride + sodium + TDS

Treatment Selector (what treat computes)

Logic order matters — treat in sequence, price the right class:

1. Bacteria positive → shock-chlorinate + fix well defect (cap, casing, grading). $0–50 DIY; UV sterilizer $800–1,500 if recurring. Disinfection precedes everything.
2. pH < 6.5 → calcite/soda-ash neutralizer ($800–1,800) — before softener, or the softener resin suffers and pipes keep corroding.
3. Iron ≤ 3 ppm → softener can remove it incidentally (with rest); 3–10 ppm → oxidizing filter (air-injection/Manganese Greensand, $900–2,200); >10 ppm or iron bacteria → chlorination + retention + filtration ($1,500–3,500). The oversold case: softener-only for 5 ppm iron = resin clogs in months.
4. Hardness > 120 → softener sized to grain load (see water-softener-sizer doctrine; $600–1,500 DIY).
5. Arsenic/nitrate/lead at level → point-of-use RO at drinking taps ($200–600) or whole-house media if whole-house contact (arsenic > 50 µg/L). Nitrate > 8 mg/L with infants: bottled water until POE/POU confirmed.
6. Whole-house RO ($4,000–15,000) — almost never. Justified only at extreme TDS/sodium/sulfate whole-house needs. The oversell-guard fires when softener+neutralizer+iron handles the report for a fraction.

Common Pitfalls

1. Free water tests from treatment companies — strips + sales script; order county/state-accredited lab panels instead.
2. Testing right after a shock-chlorination — false negatives; wait 2 weeks, run water 15 min before sampling.
3. Interpreting hardness as a health problem — it's an appliance/soap problem; don't buy a softener to "protect health."
4. Softener sold as an iron solution at >3 ppm — resin fouls; oxidizing filter is the right class.
5. Whole-house RO as a default — the biggest-ticket oversell; POU RO at the kitchen tap solves drinking-water parameters for 5% of the price.
6. Coliform-positive → treating water only — find and fix the entry (well cap, casing crack, graded ground, back-siphonage), then retest.
7. Old reports treated as current — wells change after floods, nearby drilling, and pump work; coliform is an annual test.

Verification Checklist

• Report decoded line-by-line against MCL/secondary table; every health parameter under limit
• Symptoms cross-checked (stain color → parameter) BEFORE treatment decisions
• Bacteria: absent, or well defect fixed + shock-chlorinated + retested clean
• pH ≥ 6.5 before any softener/iron equipment decision
• Treatment classes sequenced (bacteria → pH → iron → hardness → POE/POU), not bundled by sales script
• Whole-house RO justified only by whole-house parameters (extreme TDS/sodium/sulfate)
• Annual coliform + nitrate scheduled; arsenic/lead every 3–5 yr or after well work
• Quotes cross-checked against the price bands in this skill

Example Session

text

$ python3 scripts/wellwater.py decode --hardness 142 --iron 3.2 --manganese 0.4 \
    --ph 6.4 --nitrate 4.1 --tds 380 --coliform absent --arsenic 3
DECODING WELL WATER REPORT
  coliform ABSENT — good. Recheck annually.
  iron 3.2 mg/L — 11x SECONDARY LIMIT: red-brown stains, metallic taste.
    >3 ppm: oxidizing filter, NOT softener-only (resin fouls).
  manganese 0.4 mg/L — OVER HEALTH LIMIT (0.12): black stains AND
    children's neuro advisory — oxidizing filter (same unit as iron).
  hardness 142 mg/L — HARD (aesthetic): scale/soap waste. Not a health
    issue. Softener after iron/pH handling.
  pH 6.4 — BELOW RANGE: corrosive; blue-green stains, leaches
    lead/copper. Neutralizer FIRST in train.
  nitrate 4.1 / TDS 380 / arsenic 3 — fine.
TREATMENT SEQUENCE (order matters):
  1) calcite/soda-ash pH neutralizer $800-$1,800
  2) air-injection/greensand oxidizing filter (Fe+Mn) $900-$2,200
  3) ion-exchange softener sized to grain load $600-$1,500
  realistic installed total: $2,300-$5,500
OVERSELL GUARD: whole-house RO ($4,000-$15,000) is justified ONLY by
  whole-house TDS/sodium/sulfate extremes — not this report.