Water treatment in Klamath Falls, Oregon.

Klamath Falls runs on 100% groundwater from 11 city wells and disinfects with chlorine only (not chloramine), so standard activated carbon works well. The 2024 CCR reports TTHM and HAA5 as Not Detected (2024 CCR).

The filter focus in Klamath Falls is different from Rogue Valley cities: it's arsenic (up to 7.71 ppb, 1,123x EWG's health guideline), chromium-6 (0.170 ppb, 8.5x guideline), and PFOS detected at the Balsam Well at 4.7-9.5 ppt — above the 2024 EPA MCL of 4.0 ppt that the city must meet by 2029 (EWG — Klamath Falls). Standard carbon is useful for taste and odor, but the real value is a multi-stage system with a specialty arsenic stage.

Klamath Falls is the single most distinctive arsenic market in this list. The city's water comes from 11 wells in volcanic/geothermal geology; the 2024 CCR reports arsenic ranging from 2.59 to 7.71 ppb across its well field — below the 10 ppb MCL but roughly 9x the Oregon state average of 0.479 ppb, and up to 1,123x the EWG cancer health guideline of 0.004 ppb (EWG — Klamath Falls Arsenic; 2024 CCR).

USGS documented arsenic in Upper Klamath Basin waters as high as 36.7 µg/L (3.7x the federal MCL) at spring sites like Wood Kimball Spring and Fort Creek (USGS SIR 2024-5029). For private wells in the basin, this isn't hypothetical — it's the default. A point-of-use RO is the simplest home solution; whole-house adsorptive media is the right answer if more than one tap is affected.

This is the single most defensible RO market in the list. One point-of-use system addresses every significant Klamath Falls water issue at once: arsenic 2.59-7.71 ppb (1,123x EWG guideline), PFOS 4.7-9.5 ppt at Balsam Well (above the 2024 EPA MCL of 4.0 ppt, compliance required by 2029), naturally occurring fluoride 0.2-0.34 mg/L (geothermal origin), nitrate up to 3.54 mg/L at Balsam Well, chromium-6, TDS, and sulfate/sodium from geothermal-influenced aquifer chemistry (2024 CCR; EWG — Klamath Falls).

If a Klamath Falls home gets only one water-treatment product, this is it.

Klamath Falls is the only city in this list where hardness varies substantially by neighborhood, because the city draws from 11 wells with very different chemistry. From the 2024 CCR (Klamath Falls 2024 CCR):

• Conger Wellfield — 50 mg/L (~2.9 gpg)
• Debbie — 66 mg/L (~3.9 gpg)
• Fremont — 74 mg/L (~4.3 gpg)
• Hilyard — 76 mg/L (~4.4 gpg)
• Wocus — 66 mg/L (~3.9 gpg)
• Balsam — 130 mg/L (~7.6 gpg)
• Homedale — 140 mg/L (~8.2 gpg)

Homes served primarily by the Balsam or Homedale wells see genuinely hard water (7+ gpg) while homes nearer Conger Well Field are soft. A softener is a real conversation for the harder zones; we qualify by neighborhood and hardness test.

There are two interesting fits here. First, homes on the harder city wells — Balsam (~7.6 gpg) and Homedale (~8.2 gpg) — have a real scale problem.

Second, Klamath Falls is the only city in the list with 500+ private geothermal heating wells serving 600+ structures (OSTI — Klamath Falls Geothermal District Heating). Residential geothermal-loop water runs high silica (up to 100 mg/L, vs ~35 mg/L in ambient groundwater) (USGS — Low-Temperature Geothermal Waters at Klamath Falls). Silica scale is genuinely hard to control; TAC helps on the potable side, and we pair it with appropriate loop-water treatment for the geothermal side.

Klamath Falls runs a chlorine-only disinfection approach (not chloramine) on 100% groundwater from 11 city wells. Residual is low — 0.20 to 0.26 mg/L — and 2024 CCR TTHM/HAA5 came back Not Detected (2024 CCR). Standard activated carbon works well here (no need for chloramine-rated catalytic carbon).

The specific city-water concerns to design around are arsenic (2.59-7.71 ppb, up to 1,123x EWG guideline), PFOS at Balsam Well (4.7-9.5 ppt — above the new 4.0 ppt EPA MCL), chromium-6, and naturally occurring fluoride from geothermal bedrock. A point-of-use RO handles those, with whole-home carbon for taste and chlorine.

Klamath Falls uses chlorine only on 100% groundwater from city wells; the 2024 CCR measured residuals of 0.20 to 0.26 mg/L — among the lowest in this list.

The city's own CCR language is clean on this point: "we only treat the water with a single common additive, chlorine" (2024 CCR). Standard GAC carbon or carbon-block is sufficient for chlorine removal.

Klamath Falls is the only city in this list where H2S reaches past private drinking-water wells into the city's geothermal infrastructure. It sits on a Known Geothermal Resource Area, and more than 500 private geothermal heating wells serve over 600 structures (OSTI — Klamath Falls Geothermal).

Measured H2S in the geothermal water is approximately 1.5 mg/L and is documented as a primary cause of corrosion of mild steel, cast iron, copper, brass, and aluminum. While the drinking-water side of a home is separate from the geothermal loop, homes with geothermal heating deal with rotten-egg odor in the mechanical room and corrosion of anything metal the loop water touches. For private drinking-water wells, the same volcanic/geothermal geology that causes basin-wide arsenic makes H2S a realistic finding — especially in deeper wells that intersect warm groundwater.

Klamath Basin wells are in a class of their own. USGS SIR 2024-5029 documents arsenic in basin waters ranging from 0.03 to 36.7 µg/L (3.7x the EPA MCL) at spring and well sites including Wood Kimball Spring, Fort Creek, and Crooked Creek (USGS SIR 2024-5029).

The second story is drought: groundwater levels in the basin have dropped 30-60 feet since the early 2000s, and in 2021 Klamath County registered 185 dry wells by August alone (OregonLive). The county runs a Domestic Well Financial Assistance Grant covering up to $40,000 (75%) of well rehab (Klamath County — Dry or Failing Wells) — Absolute Water Filtration can coordinate with that program.

Klamath Falls well panel priorities: arsenic, uranium, fluoride (natural, geothermal source), H2S in deeper wells, nitrate in agricultural zones, pump and flow testing on any well that's seen a drought-year drop.

Klamath Falls is the only city in our service area with a documented PFAS exceedance of the new EPA MCL. The 2024 CCR reports PFOS at 4.7-9.5 parts per trillion at the Balsam well — above the 4.0 ppt MCL finalized by the EPA in April 2024 (Klamath Falls 2024 CCR; EPA PFAS Final Rule).

The city has time on the regulatory calendar — initial monitoring by 2027, full compliance by 2029 — and operational options to blend Balsam with lower-PFAS wells, take Balsam offline, or install treatment at the well head. None of those help your kitchen tap today. A point-of-use RO at the kitchen rejects 95-99% of PFOS and also handles arsenic (2.59-7.71 ppb across the city's 11 wells), naturally occurring fluoride, nitrate, and chromium-6 in a single under-sink unit (EWG — Klamath Falls).

Klamath Falls' 2024 CCR reports nitrate ranges across its 11 wells, with Balsam well at 3.54 mg/L — below the 10 mg/L MCL but among the higher city-water values in the region (Klamath Falls 2024 CCR).

For private wells in Klamath County agricultural valleys (Tulelake corridor, Lower Klamath Lake area), nitrate is a known concern and should be on every annual well panel. A point-of-use RO at the kitchen also covers Klamath Falls' arsenic and PFOS profile in one unit.

Klamath Falls city water generally runs low iron and manganese — but private wells in the basin, especially deeper geothermally influenced wells, can carry both. The Conger, Debbie, Fremont, Hilyard, and Wocus city wellfields all report measurable manganese in the 2024 CCR (Klamath Falls 2024 CCR).

For private wells with iron, manganese, or H2S, the standard treatment is a manganese greensand or Katalox Light filter sized to peak flow, with an oxidation pretreatment step where indicated.

Klamath Falls city water is chlorinated and meets bacteriological standards — UV isn't relevant for city customers. For private wells in Klamath County agricultural valleys, on the basin's outer rim, or in geothermally influenced aquifers, UV is the standard residential bacterial control after any positive coliform result.

NSF/ANSI 55 Class A UV at 40 mJ/cm² is the right specification, with sediment plus carbon prefiltration to protect lamp performance from iron and turbidity.