Executive Summary
Our field teams recorded 886 TDS readings across Nairobi and its satellite towns between October 2025 and October 2026. The data shows a consistent pattern: source water in peri-urban corridors carries a higher dissolved solids load than in central Nairobi, and the iClear purification system delivers a mean TDS reduction of 85.1%, calculated across the 640 readings with measurable purified output rather than all 886 readings.
This report presents field TDS readings collected by iClear Wellife Service Limited during routine technician visits to active customer sites across Nairobi and nearby towns. It is published as part of iClear's commitment to transparency, and as a contribution to the evidence base on source-water mineral load in Nairobi's urban and peri-urban areas. Note: these readings were taken at iClear customer homes using handheld meters, not by a laboratory or an independent monitoring body, and the locations are not a random sample of Nairobi households.
TDS is a measure of all dissolved inorganic and organic substances in water, expressed in milligrams per litre (mg/L). It is a useful field screening indicator of total dissolved solids. It does not identify individual substances or directly measure hardness, and it does not by itself establish whether water is safe or unsafe for drinking. For a comprehensive safety assessment, full laboratory analysis is required. No national TDS limit is applied in this report. The 500 mg/L value used here is an analytical threshold chosen for this report. Readers should consult the Kenya Bureau of Standards (KEBS) for the current drinking water standard that applies to them.
Key Findings at a Glance
Finding
Figure
Total field readings analysed
886
Date range
October 2025 to October 2026
Unique locations sampled
325 (distinct standardised location names, from 417 name variants as recorded)
Mean source-water TDS (all locations)
228.5 mg/L
Readings above 500 mg/L analytical threshold
115 (13.0%)
Mean TDS after iClear purification
27.3 mg/L (non-zero readings)
Mean TDS reduction by iClear system
85.1% (based on the 640 readings with measurable output, not all 886)
Highest source-water TDS recorded
993 mg/L (Peri-urban South/East, September 2026)
Zone with highest average TDS
Peri-urban South/East: 374 mg/L average
Zone with lowest average TDS
Northern satellite towns and Nairobi West/Central (comparable, ~165 mg/L)
Methodology and Data Sources
How the Readings Were Collected
All readings in this report were taken by iClear's field technicians during routine service visits to active customers. Technicians recorded TDS using calibrated handheld TDS meters, taking measurements at two points: immediately before the iClear purification unit (source water) and immediately after (purified output). Readings were logged against a date, location name and technician identifier.
The data covers 13 calendar months, from October 2025 to October 2026. The vast majority of readings are from Nairobi and its satellite towns, grouped into five geographic zones for analysis: Nairobi West and Central (primarily municipal supply), Northern satellite towns (Ruiru, Kiambu, Ruaka), the Ngong/Langata/Rongai corridor, Eastlands, and the peri-urban South/East corridor (primarily the Kitengela, Katani and Athi River areas). Three readings were recorded in Mombasa; these are included in the total but are too few to support geographic conclusions about Mombasa.
What TDS Measures and Its Limitations
Total Dissolved Solids measures the concentration of all dissolved inorganic and organic substances in water, expressed in milligrams per litre (mg/L) or parts per million (ppm). Higher TDS indicates a greater concentration of dissolved substances, which may include minerals such as calcium and magnesium. TDS readings alone cannot identify the substances present or show whether harmful contaminants are present.
TDS is used in this report as a field-measurable indicator of dissolved solids load. It does not directly measure specific heavy metals, organic chemicals or pharmaceutical residues, all of which require laboratory analysis. Readings at 0 mg/L in the after-column indicate a reading below the detection threshold of the meter, not an absence of all dissolved matter.
Palatability ratings. This report uses the WHO palatability ratings for total dissolved solids, as set out in the WHO background document on total dissolved solids (https://www.who.int/docs/default-source/wash-documents/wash-chemicals/total-dissolved-solids-background-document.pdf): below 300 mg/L excellent; 300 to 600 mg/L good; 600 to 900 mg/L fair; 900 to 1,200 mg/L poor; above 1,200 mg/L unacceptable. These are palatability ratings, not health-based safety standards.
Technicians
Readings were recorded by iClear's field technician team. Two technicians accounted for the majority of readings across the full 13-month period. Data was cleaned to normalise technician name variants before analysis.
Data Limitations
Readers should interpret the findings in this report in light of the following limitations, which apply throughout:
These are handheld TDS meter readings, not laboratory-verified results. Handheld meters measure electrical conductivity as a proxy for dissolved solids and are subject to calibration drift, temperature variation and operator technique. They are appropriate for field screening but should not be treated as equivalent to accredited laboratory analysis.
All readings were taken at the homes or offices of active iClear customers. This is not a random sample of Nairobi households or of any defined geographic area. Properties without a water purifier, and areas outside iClear's service footprint, are not represented.
The dataset does not record whether each source reading came from piped municipal water, a private borehole, a rainwater tank, or another source. Geographic differences in TDS therefore reflect a mix of source-type differences and location differences, and these cannot be separated from the data alone.
Location names were entered by technicians in the field without a standardised list. The same location may appear under slightly different spellings. Analysis groups these variants where clearly referring to the same area, but the groupings involve judgment calls and may not always be precise.
The geographic coverage is concentrated in Nairobi and its satellite towns. Three readings are from Mombasa. Findings should not be generalised beyond Nairobi and the specific satellite-town corridors represented in the data.
5 after-purification readings above 100 mg/L are present in the verified dataset. These represent a small proportion of readings and are discussed in the Purification Performance section.
Findings: Overview of Source-Water Quality
TDS Distribution Across All 886 Readings
The 886 source-water readings span a range of 2 to 993 mg/L, with a mean of 228.5 mg/L. Figure 1 shows the distribution against the 500 mg/L analytical threshold and the 300 mg/L reference point.
72.5% of all readings fell below 300 mg/L, the WHO 'excellent' palatability band. A further 20.5% fell in the 300 to 600 mg/L range ('good'), 6.4% in the 600 to 900 mg/L range ('fair'), and 0.6% in the 900 to 1,200 mg/L range ('poor'). No reading exceeded 1,200 mg/L, the level rated 'unacceptable'.
Figure 1: Distribution of source-water TDS readings across 886 field measurements, October 2025 to October 2026. 27.5% of all readings were at or above 300 mg/L.
115 out of 886 source-water readings (13.0%) exceeded 500 mg/L, the analytical threshold used in this report. Most of these readings were in the peri-urban South/East corridor.
Monthly Trend: Higher Average TDS in Mid-2026
The monthly data shows higher average source-water TDS in July and August 2026, at 305 and 300 mg/L respectively, compared to a 13-month average of 229 mg/L. Two factors may contribute to this and cannot be separated in the current dataset. First, July and August correspond to Kenya's dry season, during which reduced rainfall dilution can concentrate dissolved minerals in groundwater and surface water sources. Second, the sample composition also shifted in those months: Kitengela-area readings made up a larger share of the July dataset than in other months, and Kitengela consistently records the highest TDS values in this dataset.
October 2025 to June 2026 showed relatively stable average TDS values between 183 and 248 mg/L. Whether the July and August peaks represent a genuine seasonal effect or a shift in where technicians were working cannot be determined from TDS readings alone. Readers should treat any seasonal interpretation as preliminary.
Figure 2: Monthly average source-water TDS across all locations, October 2025 to October 2026. The 500 mg/L analytical threshold (dashed red) and 300 mg/L reference point (dotted orange) are shown. Bars in orange indicate months where the average exceeded 300 mg/L. *October 2026 data is partial (59 readings to 19 October).
Findings: Geographic Variation
The table below groups the 886 verified readings by geographic zone. Each zone shows the number of readings, average source-water TDS, the number and share of readings above the 500 mg/L analytical threshold, and the average purified output for readings above zero.
Table 1: Readings by geographic zone (886 verified field readings)
Zone
Readings
Share of readings
Mean source TDS (mg/L)
Readings above 500 mg/L
Share above 500 mg/L
Mean purified TDS, non-zero (mg/L)
Nairobi West and Central (municipal supply)
144
16.3%
165.7
12
8.3%
18.5
Northern satellite towns (Ruiru, Kiambu, Ruaka)
130
14.7%
164.6
7
5.4%
20.3
Ngong / Langata / Rongai corridor
122
13.8%
214.3
11
9.0%
26.3
Eastlands
92
10.4%
175.4
5
5.4%
29.2
Peri-urban South/East (Kitengela, Katani, Athi River)
219
24.7%
374.2
67
30.6%
37.4
Mombasa and other outlying
3
0.3%
463.3
2
66.7%
21.7
Not assigned to a zone
176
19.9%
179.3
11
6.2%
24.1
Total
886
100.0%
228.5
115
13.0%
27.3
Peri-urban South/East: The Highest-TDS Zone in This Dataset
The most striking geographic pattern in the dataset is the consistently elevated TDS in the peri-urban South/East zone, anchored by Kitengela, Katani, Syokimau, Greatwall and surrounding areas. With a zone average of 374 mg/L from 219 readings, this corridor records more than twice the average TDS of central Nairobi. 30.6% of all readings from this zone exceeded the 500 mg/L analytical threshold.
Kitengela alone accounts for 37 readings (treating capitalisation variants as one location) with an average TDS of 546 mg/L. The dataset does not record source type or underlying geology, so the reasons for higher readings in this corridor cannot be established from these readings alone.
Other high-TDS locations in this zone include Katani (average 411 mg/L across 29 readings) and Greatwall (361 mg/L average across 36 readings). Syokimau recorded an average of 374 mg/L across 20 readings.
Figure 3: Left: Average source-water TDS by geographic zone. Right: Percentage of readings above the 500 mg/L analytical threshold by zone. The Peri-urban South/East zone is the most significant outlier on both measures.
Nairobi West and Central: Mostly Low TDS, with Exceptions
The 144 readings from Nairobi West and Central (Lavington, Kilimani, Parklands, Kileleshwa, Riverside, Westlands and surrounding areas) show a zone average of 166 mg/L, comparable to the 165 mg/L average in the Northern satellite towns and below the Eastlands and Ngong/Langata/Rongai zones. Only 8.3% of readings in this zone exceeded the 500 mg/L analytical threshold. Source type is not recorded in the dataset for these readings.
However, within this generally low average, outliers exist. A reading of 837 mg/L was recorded at one location in this zone. The dataset does not record the cause. This underscores the point that zone averages can obscure significant household-level variation. Even in well-served areas of central Nairobi, individual locations may experience substantially elevated TDS.
Northern Satellite Towns: Moderate with Notable Peaks
Ruiru, Kiambu, Ruaka and nearby northern satellite towns returned a zone average of 165 mg/L from 130 readings, with 5.4% of readings exceeding 500 mg/L. Individual outliers reached 706 mg/L. The variation within this zone may reflect differences in source type, which the dataset does not record.
Table 2: Selected Locations: TDS Comparison
Location
Readings
Avg TDS (mg/L)
Max TDS (mg/L)
% above 500
Kitengela (all variants)
37
546
983
62%
Katani
29
411
800
38%
Greatwall
36
361
892
31%
Syokimau
20
374
531
10%
Kiserian
8
348
793
25%
Rongai
11
313
819
9%
Ngong
6
303
706
33%
Fourways
18
292
706
11%
Parklands
21
126
428
0%
Findings: iClear Purification Performance
Mean TDS Reduction of 85.1%
Across all 640 paired readings where the after-purification TDS was above zero (246 readings recorded 0, indicating a result below the meter's detection threshold), the mean TDS reduction achieved by the iClear system was 85.1%. This is measured from the source-water reading to the purified output at the same service visit.
The mean output TDS from readings above zero was 27.3 mg/L. For the 246 readings where the output registered at 0 mg/L on the meter, the actual output TDS is below the meter's detection threshold, indicating an even higher effective rejection rate. If these are conservatively counted as 1 mg/L, the adjusted mean output across all 886 readings would be an estimated 20 mg/L.
The mean output of 27.3 mg/L from non-zero readings sits well within the WHO 'excellent' palatability band (below 300 mg/L), and far below the 500 mg/L analytical threshold used in this report.
Performance Across the Full Source-Water Range
Purification remained measurable even at very high source-water TDS levels. Kitengela readings, where source water regularly exceeds 500 mg/L and reached 983 mg/L in this dataset, produced purified output with a median of 31 mg/L across 37 readings. These results are consistent with the membrane and multi-stage design of the iClear system, but the dataset does not record servicing status, so the effect of maintenance cannot be separated out.
The scatter plot below shows the relationship between source-water TDS and post-purification TDS for all 886 field readings. Purified output stays low across much of the source-water range shown.
Figure 4: Source-water TDS vs. purified output TDS for all 886 field readings. The 50 mg/L reference line (dashed green) is shown for reference. Points at 0 on the y-axis represent readings below meter detection. Colour indicates output level: green (0-50 mg/L), orange (51-100 mg/L), red (>100 mg/L).
Readings Where Output Exceeded 100 mg/L
5 readings in the verified dataset produced an after-purification TDS above 100 mg/L, representing 0.6% of all 886 readings. All five customers were followed up by iClear's service team. In each case, output TDS returned to the normal range with continued use.
Table 3: Readings with purified output above 100 mg/L
Location
Before TDS
After TDS
Reduction
Note
Utawala
580
356
39%
Followed up by iClear – output returned to normal range
Ngong area
170
139
18%
Followed up by iClear – output returned to normal range
Kitengela
772
136
82%
Followed up by iClear – output returned to normal range
Kitengela
307
123
60%
Followed up by iClear – output returned to normal range
Fourways
239
120
50%
Followed up by iClear – output returned to normal range
Implications for Households and Policy
High Mineral Load Is Concentrated, But Not Confined to Peripheral Areas
The data shows that the highest source-water TDS in this dataset is concentrated in the peri-urban South/East corridor, particularly Kitengela, Katani and Athi River. The dataset does not record source type for households in this corridor. Source water in these locations frequently exceeds the 500 mg/L analytical threshold.
The data also shows that elevated TDS is not exclusive to peripheral areas. Outlier readings in Kilimani show that individual locations within well-served central Nairobi neighbourhoods can record high mineral loads, although the dataset cannot confirm the cause of individual high readings.
What Elevated TDS Means in Practice
A TDS reading above 500 mg/L does not automatically indicate a health hazard. It indicates a higher concentration of dissolved solids and may affect taste. TDS alone cannot establish whether specific contaminants are present.
TDS analysis is a screening tool. Households in the Kitengela area and similar peri-urban zones should follow TDS readings with full laboratory analysis including pH, fluoride, nitrate, hardness, iron and bacteriological parameters to obtain a complete picture of their water quality.
The Case for Point-of-Use Treatment
Households cannot assume consistent quality at the tap, because source water can vary considerably. A point-of-use filter can reduce the mineral load of the water at the tap, but its performance depends on regular maintenance and filter replacement.
Recommendations
For Households
If you are in the Kitengela, Athi River, Katani or Greatwall areas and relying on borehole water without treatment, have your water tested for the full parameter panel (TDS, pH, fluoride, nitrate, hardness, iron, E. coli) from a KENAS-accredited laboratory.
If you notice a change in taste, or your purified water reading is noticeably higher than usual, contact iClear to schedule a system check.
Service your system on the recommended schedule, with an extra check if your water source or taste changes.
Do not use TDS alone as a proxy for microbiological safety. A high TDS reading calls for full laboratory testing, not just purification.
For the Water Sector
Municipal authorities should consider extending piped, treated water supply to the Kitengela and Athi River areas, given the elevated TDS readings observed in this dataset.
Water quality monitoring in peri-urban areas should move from point-of-production (treatment plant) to point-of-consumption (household tap). The findings highlight the value of more systematic household-level water quality monitoring in peri-urban areas.
Kenya's national water quality monitoring framework should incorporate field data from private operators, which can supplement the limited coverage of government monitoring programmes.
About iClear Kenya
iClear Wellife Service Limited is a Nairobi-based water purification company providing multi-stage reverse osmosis purification systems to households and offices in Nairobi and its satellite towns. The company's service model is built on regular technician maintenance visits, which are the source of the field readings in this report.
iClear's systems use multi-stage filtration, including sediment pre-filters, activated carbon stages and a reverse osmosis membrane, to reduce TDS. The standard iClear product is designed to handle source water with TDS levels in the range encountered across Nairobi and its satellite towns.
For more information: iclear.co.ke
About This Report
This report was produced by Shadow Creative Group Limited on behalf of iClear Wellife Service Limited, under the terms of the Year Two Service Agreement between the two organisations. The data was collected by iClear's field team. Statistical analysis and report writing were conducted by Shadow Creative Group.
This is the first publication in what is intended to be a quarterly series. Q4 2026 data collection is ongoing. The next report will extend the series to include the October to December 2026 period.
This inaugural report establishes a 13-month baseline dataset (October 2025 to October 2026). Subsequent reports will follow quarterly reporting periods.
The authors note that this report presents TDS as the sole measured parameter. It does not claim to represent bacteriological, chemical or full mineral safety of the water sources described. Readers seeking comprehensive water quality assessments should commission full laboratory analysis from a KENAS-accredited facility.
Shadow Creative Group is a Nairobi-based creative agency providing SEO, branding and digital communications services.
To download the PDF version of the report, click here: iClear Q3 2026 Water Quality Report: Drinking Water Quality in Nairobi and Satellite Towns
Report reference: iClear-WQR-Q3-2026
Published: October 2026 | Nairobi, Kenya
Data collection period: October 2025 to October 2026
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