How AI Search Is Recommending Water Filter Systems: Monthly Trends

Executive Summary

Aquasana holds the category lead in October 2026 with 57.6% valid recommendation coverage, extending its run at the top of the benchmark. The gap to the next brand, iSpring at 50.2%, stands at 7.4 points, wider than the 4.6-point separation recorded in September 2026. Because the current leader's own baseline-to-current change of up 2.2 points from 55.4% in July 2026 sits inside normal month-to-month variation, the leadership position is best read as stable rather than newly won.

Brita is the strongest riser across the series, up 11.3 points to 46.3% valid recommendation coverage from 35.0% in July 2026, a significant gain on a three-month upward streak. The brand's top-three rate rose 19.1 points to 29.7% over the same window, and its rank-one rate rose 5.7 points to 8.4%. Culligan, up 9.5 points to 39.1% from 29.6% in July 2026, and Clearly Filtered, up 5.6 points to 34.9% from 29.3%, complete a three-brand set of significant risers.

iSpring is the sharpest decliner of the series, down 9.2 points to 50.2% valid recommendation coverage from 59.4% in July 2026, a significant decline that moved the brand out of the top spot it held at baseline. Berkey fell 6.9 points to 7.3% from 14.2% in July 2026, also significant, and has now declined for three consecutive months. APEC Water Systems recorded a third consecutive monthly down and is classified as a watch item, though its cumulative change remains within normal variation.

Against the prior month, the category was mixed but quiet: no brand posted a significant single-month move between September 2026 and October 2026. The cumulative July-to-October window, by contrast, shows three significant risers (Brita, Clearly Filtered, Culligan) and two significant decliners (Berkey, iSpring).

Each monthly run begins with 800 prompt-surface observations (604 unique questions) across the benchmark's defined AI/search surface universe in October 2026. All 800 prompts mentioned a tracked brand or competitor; 796 were relevant and 4 were irrelevant. The public metrics use the 713 qualified observations that survive both qualification stages. The baseline month, July 2026, followed the same structure with 800 prompt-surface observations (552 unique questions), 800 brand mentions, 797 relevant and 3 irrelevant prompts, and 697 qualified observations. August 2026 recorded 703 qualified observations and September 2026 recorded 717 on the same funnel.

Key Findings

AI Response Inconsistency Alerts

Questions This Section Answers

• Which water filter brands had conflicting AI answers this month?
• What kinds of factual claims did the platforms disagree on?

Five critical or high-severity factual inconsistencies were detected across five AI platforms, spanning four tracked companies.

Clearly Filtered

AI platforms provided conflicting information about the price of the Clearly Filtered pitcher. When asked "What is the best water filter pitcher that works?", Google AI Mode stated the pitcher costs roughly $255 to $290, while Google AI Overviews stated $110.00. The two responses cited different source sets: Google AI Mode referenced the company's own product page, a YouTube review, and a third-party review site, while Google AI Overviews cited CNN and a competing brand's explainer page. A flagged source excerpt from the Clearly Filtered product page shows "Filtered Water Pitcher $110.00," and a second flagged excerpt from a review site lists a unit cost of $110.

A second high-severity conflict on the same topic produced a different pairing. When asked the same question, Google AI Mode again stated roughly $255 to $290, while Gemini stated approximately $90 upfront. Gemini's response drew on a different set of sources, including a third-party testing site and a non-toxic product lab. Responses differed on the same product's price by a factor of nearly three.

APEC Water Systems

AI platforms provided conflicting information about who makes APEC Water Systems. When asked "Who makes APEC Water Systems?", ChatGPT stated that APEC is a privately owned U.S. water filtration company, Advanced Purification Engineering Corp., citing the company's own about page. Copilot stated that APEC is part of Culligan Corporate's portfolio, referencing the APEC homepage, about page, and products page. A flagged source excerpt from the APEC about page reads: "APEC, Advanced Purification Engineering Corp. APEC is the leading manufacturer of residential reverse osmosis drinking water filtration systems in the United States." Both ownership claims cannot be true simultaneously.

Brita

AI platforms provided conflicting information about contaminant removal. When asked "What water filter brand actually works?", Google AI Overviews stated that the Brita Denali with the Elite filter is certified to reduce lead, chlorine, and PFAS, while basic Brita models only improve taste. Copilot stated that pitcher filters such as Brita and PUR improve taste but do not remove heavy metals or PFAS. Google AI Overviews cited YouTube reviews and a shopping result, while Copilot cited a water filter review site, a home improvement site, and a water treatment provider. One flagged source excerpt from a review site reads: "Basic pitcher filters (NSF 42) only address aesthetics like chlorine taste and fail to meet clinical-grade safety thresholds for heavy metals or PFAS."

PUR

AI platforms provided conflicting information about PFAS removal capability. When asked "What pitcher removes forever chemicals?", Gemini stated that certain PUR Plus filter models, such as PPF951K, carry NSF/ANSI 53 certification to reduce total PFAS. Copilot stated that standard Brita or PUR pitchers do not remove PFAS. Gemini cited a PFAS-focused newsletter and two filter review sites, while Copilot cited a PFAS water filter guide and two Amazon listings for a competing Culligan pitcher. One flagged source excerpt supports the certification claim: "IAPMO lists ZR-0810N for PFOA and PFOS and PPF951K for total PFAS."

Benchmark Context

Questions This Section Answers

• What is the difference between the raw prompt collection and the 713 qualified benchmark observations?
• How has the size of the qualified benchmark set changed since July 2026?

The report separates the raw collection universe from the qualified analysis set. Brand-level recommendation percentages are calculated within the qualified benchmark set.

August 2026 recorded 703 qualified observations and September 2026 recorded 717, both on the same funnel structure. The qualified benchmark observations count is the denominator for every brand-level rate reported in this article.

Benchmark-Level Metrics

The recommendation-shaped answer share climbed sharply across the series, from 53.2% in July 2026 to 75.2% in October 2026, with the largest single jump occurring in the current month. September 2026 sat at 51.9% and August 2026 at 52.8%. The valid recommendation shortlist share similarly rose from 84.1% to 94.1%, meaning a larger proportion of qualified observations now carry a usable recommendation signal than at any earlier point in the series.

AI Recommendation Trend

Questions This Section Answers

• Which water filter brand leads the category in October 2026, and how wide is the gap to second place?
• Which brands rose and which fell across the July-to-October window?

Aquasana holds the lead as Brita and iSpring converge toward the top and the mid-tier compresses

No brand exceeded normal month-to-month variation between September 2026 and October 2026. The category-level picture moved through a combination of several smaller movements, most notably Aquasana's 4.2-point prior-to-current gain and iSpring's 1.4-point prior-to-current gain against its steep cumulative decline.

What Changed This Month

Questions This Section Answers

• Why is Aquasana's lead described as stable rather than newly won?
• Which water filter brands gave back part of their September highs even though they remain series risers?
• Why should Pentair's 3.4% coverage and 0.3% rank-one rate be read alongside their underlying observation counts?

Aquasana holds the lead as its top-three rate climbs sharply

Aquasana led the category in October 2026 with 57.6% valid recommendation coverage, up 2.2 points from 55.4% in July 2026, a change within normal month-to-month variation. The month-over-month movement was also modest, up 4.2 points from 53.4% in September 2026, within normal month-to-month variation. The brand has now been classified as stable at the series level, with its lead described by the benchmark as stable.

The more notable shift sits beneath the headline number. Aquasana's top-three rate rose 14.1 points to 47.1% from 33.0% in July 2026, a significant gain, while its rank-one rate rose 3.5 points to 13.3%, also significant. Its presence rate held flat at 65.5%, down 0.5 points from 66.0% in July 2026.

Aquasana is converting existing presence into stronger placement rather than expanding its footprint. The brand appears in roughly the same share of prompts as at baseline but is named in the top three far more often. Presence and placement strength are moving on different tracks, and the placement track is now the stronger of the two.

Highest-priority diagnostic: Which prompt types drove the 14.1-point top-three gain, and is the improvement concentrated in particular surfaces?

Brita is the largest cumulative riser, with its gain running through every placement layer

Brita rose 11.3 points to 46.3% valid recommendation coverage from 35.0% in July 2026, a significant gain and the largest cumulative rise in the series. The brand has now risen for three consecutive months, from 35.0% in July 2026 to 35.9% in August 2026, 41.6% in September 2026, and 46.3% in October 2026. The month-over-month gain of 4.7 points from September 2026 was not itself significant.

The rise ran through every layer. Brita's presence rate rose 6.6 points to 64.0% from 57.4% in July 2026, a significant gain; its top-three rate rose 19.1 points to 29.7% from 10.6%, also significant; and its rank-one rate rose 5.7 points to 8.4% from 2.7%, also significant. The brand recorded 330 valid recommendations in October 2026, up from 244 in July 2026.

Brita's movement is unusually broad, touching breadth and both placement tiers at once. That pattern distinguishes it from brands whose gains sit only in presence or only in top-three. The rank-one rate, while improved, still trails the top-three rate by a wide margin, which suggests first-position recommendations remain the least developed part of the brand's position.

Highest-priority diagnostic: Which prompts and surfaces produced the 19.1-point top-three gain, and why does rank-one conversion lag so far behind it?

iSpring is the sharpest cumulative decliner and has been overtaken by Brita's trajectory

iSpring fell 9.2 points to 50.2% valid recommendation coverage from 59.4% in July 2026, a significant decline. The month-over-month change between September 2026 and October 2026 was a gain of 1.4 points to 50.2% from 48.8%, within normal variation and marking a one-month upward reading. The brand's series moved from 59.4% in July 2026, down to 56.9% in August 2026, down to 48.8% in September 2026, and back up to 50.2% in October 2026.

The decline is concentrated in presence. iSpring's presence rate fell 12.7 points to 54.4% from 67.1% in July 2026, a significant decline, while its top-three rate fell 4.5 points to 35.1% and its rank-one rate fell 2.3 points to 13.5%, neither of them significant. The brand recorded 358 valid recommendations in October 2026, down from 414 in July 2026.

iSpring's position narrowed in breadth while its placement strength held largely intact. The brand still carries the second-highest top-three rate in the category at 35.1% and a rank-one rate of 13.5%, both above where Brita now sits. The distinction between appearing less often and being positioned less favorably is the central feature of its current position.

Highest-priority diagnostic: Which prompt classes account for the 12.7-point presence decline, and does the October uptick mark the end of the contraction or a single-month reading?

Brita and iSpring have converged every month of the series

The gap between Brita and iSpring closed from 24.4 points in July 2026 to 3.9 points in October 2026, a convergence of 20.5 points that occurred in every month of the series. The two brands began the window at opposite ends of the upper tier and now sit within four points of each other.

The movement is the product of two separate trajectories rather than a single event: Brita's three-month climb and iSpring's contraction from its July 2026 peak. The benchmark presents this as a category observation about competitive repositioning in the upper tier.

The upper tier of the category has rearranged around a durable leader and a tightening group beneath it. Aquasana's lead has held while the brands below it have traded position.

Highest-priority diagnostic: Which prompt types and surfaces now produce the closest Brita and iSpring results, and which brand holds the advantage in each?

Berkey's decline extends to a third consecutive month

Berkey fell 6.9 points to 7.3% valid recommendation coverage from 14.2% in July 2026, a significant decline and the brand's third consecutive down month. The month-over-month change was a further 1.1 points down from 8.4% in September 2026, within normal variation. The brand's series moved from 14.2% in July 2026, to 11.5% in August 2026, to 8.4% in September 2026, to 7.3% in October 2026.

The decline is concentrated in sentiment rather than presence. Berkey's presence rate fell 2.6 points to 16.8% from 19.4% in July 2026, not significant, while its top-three rate held essentially flat, up 0.3 points to 3.6%. The brand recorded 52 valid recommendations in October 2026, down from 99 in July 2026. Its net sentiment score fell to 0.4 from 0.8 at baseline.

Berkey's coverage is contracting while its small placement rates hold steady. With 52 valid recommendations in the current month, the brand sits on a small base, which makes percentage movement more volatile at this level of the category.

Highest-priority diagnostic: Why did the valid recommendation count halve across the series while the top-three rate held flat, and which prompts still carry the brand?

The gap between Berkey and Brita widened in the opposite direction

The separation between Berkey and Brita widened from 20.8 points in July 2026 to 39.0 points in October 2026, with the gap growing in every month of the series. The movement runs in the opposite direction to the Brita and iSpring convergence: one brand's decline and another's rise have pushed them progressively further apart.

The lower tier of the category has separated further from the mid-tier over the four-month window. The benchmark presents this as a category-level observation rather than a single brand's issue.

Highest-priority diagnostic: Which prompt and surface combinations still place the two brands in the same answer, and how often does that occur?

APEC Water Systems posts a third consecutive monthly down inside normal variation

APEC Water Systems fell 3.1 points to 33.5% valid recommendation coverage from 36.6% in July 2026, a change within normal month-to-month variation. The month-over-month change was a further 0.1 points down from 33.6% in September 2026. The brand has now declined in three consecutive months, from 36.6% in July 2026 to 33.9% in August 2026, 33.6% in September 2026, and 33.5% in October 2026, with the cumulative move still inside normal variation. The benchmark classifies the brand as a watch item.

Placement moved in the other direction. APEC Water Systems' top-three rate rose 1.2 points to 24.4% from 23.2% in July 2026, and its rank-one rate rose 3.2 points to 14.7% from 11.5%. Both gains sat inside their thresholds. The brand's presence rate fell 3.7 points to 36.2% from 39.9%. It recorded 239 valid recommendations in October 2026, down from 255 in July 2026.

APEC Water Systems is being positioned higher even as its coverage drifts down. The rank-one rate of 14.7% is the highest in the category, above Aquasana's 13.3% and iSpring's 13.5%. The distinction between ranking first when named and being named at all is the defining feature of the brand's position.

Highest-priority diagnostic: Which prompt types account for the three-month coverage drift, and why is the rank-one rate rising while coverage narrows?

Culligan and Clearly Filtered both rose significantly across the series

Culligan rose 9.5 points to 39.1% valid recommendation coverage from 29.6% in July 2026, a significant gain. The month-over-month change between September 2026 and October 2026 was 2.0 points down from 41.1%, within normal variation and a one-month reversal after a string of gains. The brand's top-three rate rose 16.7 points to 27.6% from 10.9%, its rank-one rate rose 3.0 points to 5.3% from 2.3%, both significant, and its presence rate rose 12.3 points to 53.9% from 41.6%, also significant. It recorded 279 valid recommendations in October 2026, up from 206 in July 2026.

Clearly Filtered rose 5.6 points to 34.9% valid recommendation coverage from 29.3% in July 2026, a significant gain. The month-over-month change was 3.7 points down from 38.6% in September 2026, within normal variation. Its presence rate rose 12.0 points to 44.6% from 32.6%, its top-three rate rose 11.2 points to 25.7% from 14.5%, and its rank-one rate rose 4.1 points to 8.8% from 4.7%, all significant. It recorded 249 valid recommendations in October 2026, up from 204 in July 2026.

Both brands made broad-based gains across the series and both gave back a portion of their September 2026 high in October. The distinction between a cumulative series gain and a single-month pullback matters here: the baseline-to-current classification remains a significant rise for each brand even as the most recent month reads down.

Highest-priority diagnostic: For Culligan, what separates its 27.6% top-three rate from its 5.3% rank-one rate? For Clearly Filtered, is the September-to-October pullback confined to particular prompt types?

PUR held stable with placement gains beneath a flat headline

PUR rose 4.6 points to 43.2% valid recommendation coverage from 38.6% in July 2026, a change within normal month-to-month variation. The month-over-month change was a gain of 3.2 points from 40.0% in September 2026, also within variation. The brand has recorded two consecutive monthly gains. Its top-three rate rose 9.1 points to 21.9% from 12.8%, a significant gain, and its rank-one rate rose 2.6 points to 6.6% from 4.0%, also significant. Its presence rate held essentially flat, up 0.8 points to 55.3% from 54.5%. It recorded 308 valid recommendations in October 2026, up from 269 in July 2026.

PUR's gains sit in placement rather than breadth. The 9.1-point top-three rise is the largest movement beneath its stable headline, and it mirrors APEC Water Systems' pattern of improving position without expanding footprint.

Highest-priority diagnostic: Which prompts drove the 9.1-point top-three gain, and is PUR now competing for the same list positions as Brita?

SpringWell Water and Pentair held steady at the lower end

SpringWell Water fell 3.5 points to 18.4% valid recommendation coverage from 21.9% in July 2026, within normal month-to-month variation. The month-over-month change was a gain of 0.3 points from 18.1% in September 2026. Its top-three rate fell 0.8 points to 12.3%, and its rank-one rate fell 1.8 points to 6.2%, both inside their thresholds. It recorded 131 valid recommendations in October 2026, down from 153 in July 2026.

Pentair recorded 3.4% valid recommendation coverage in October 2026, unchanged from 3.4% in July 2026. The month-over-month change was a gain of 1.5 points from 1.9% in September 2026, within normal variation and the brand's second consecutive monthly up. Its presence rate rose 2.2 points to 9.4% from 7.2%, its top-three rate rose 0.6 points to 1.7% from 1.1%, and its rank-one rate rose 0.2 points to 0.3% from 0.1%. It recorded 24 valid recommendations in October 2026, unchanged from 24 in July 2026.

Pentair's 3.4% coverage rests on 24 valid recommendations and its rank-one rate of 0.3% rests on two observations. Small counts make percentage movement inherently volatile at this level, and the flat series reading should be read alongside those absolute counts.

Highest-priority diagnostic: Which small prompt set carries Pentair's recommendations, and does the two-month upward reading hold next month?

Buyer-Intent Interpretation

Questions This Section Answers

• Which buyer-intent clusters does the public benchmark actually capture?
• What can the benchmark not yet say about how water filter recommendations shift when price or head-to-head comparison enters the question?

All 713 qualified observations in October 2026 fell into the Brand Recommendation cluster, consistent with all 717 in September 2026, 703 in August 2026, and 697 in July 2026. The benchmark captured no observations in the Pricing & Value or Multi-Brand Comparison clusters in any month of the series. The public benchmark therefore measures which brand AI recommends for a category-level ask, but it cannot yet answer how those recommendations shift when price, value, or head-to-head comparison enter the question. The five pricing and contaminant-removal conflicts documented in this month's alert section illustrate the same gap from a different angle: brand-level price and performance claims appear in platform answers, but the public benchmark's qualified observations do not yet include a pricing or comparison cluster in which to measure them.

Brand Opportunity Summary

The benchmark identifies where attention is warranted; a company-level analysis is needed to explain why.

Evidence Behind the Benchmark

Questions This Section Answers

• What prompt-level data underlies the aggregate coverage and ranking metrics?
• Does the benchmark treat source presence as proof that a source caused the recommendation?

The aggregate metrics are built from prompt-level observations (query, surface, recommendation outcome, rank, sentiment, and citations where exposed). Company-level analysis can go deeper into prompt, competitor, surface, and evidence patterns. Source presence is not automatically treated as proof of causation.

About This Benchmark

This report is part of the CiteWorks Studio LLM Authority Index AI Visibility Market Discovery research program.

• AI Visibility Industry Market
• AI Visibility Industry Market Methodology
• AI Visibility Industry Market Metrics
• AI Visibility Industry Market Standards

Report-Specific Interpretation Notes

• Small-count movement: Pentair's 3.4% coverage reflects 24 valid recommendations in October 2026, and its rank-one rate of 0.3% rests on two observations. Berkey's 7.3% coverage reflects 52 valid recommendations, down from 99 in July 2026. Small denominators make percentage movement more volatile.
• Qualified denominator vs raw collection: All recommendation percentages use the qualified set of 713 observations (October 2026), 717 (September 2026), 703 (August 2026), and 697 (July 2026), not the 800 raw prompt-surface runs. The qualified set excludes prompts that did not mention a tracked brand or were judged irrelevant.
• Directional analysis: The benchmark treats month-over-month movement as a signal for investigation, not as proof of cause. October 2026 produced no significant single-month movers on the primary metric, while the cumulative window shows three significant risers and two significant decliners. Explaining why those movements occurred requires a deeper, company-level analysis of prompts, surfaces, and evidence sources.

Next Step

The Public Benchmark Shows Where a Brand Is Winning or Losing. A Company-Level Audit Shows Why.

The aggregate percentages in this report raise questions the public benchmark cannot answer. Which high-intent prompts is a brand winning, and which competitor takes the recommendation when it loses? A brand like iSpring that fell 9.2 points across the series needs to know whether its presence decline is concentrated in specific prompt types or surfaces, and which of the rising brands captured those mentions. A brand like Brita that rose 11.3 points needs to know whether its top-three gains are durable or concentrated in a narrow prompt set. A brand like APEC Water Systems, whose coverage drifted down for three months while its rank-one rate rose, needs to know which of those two readings better reflects its actual position.

The public percentage cannot identify the prompts, competitors, or sources causing the result. A company-specific AI visibility audit maps prompt, surface, competitor, ranking, sentiment, and evidence-source patterns into a prioritized visibility strategy. It turns the benchmark's directional signals into a concrete action plan.

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