Sample reportsEL-2026-04829 · Sample report

Tap water · Westminster Jug filter · Performance

Independent water analysis · London

EL-2026-04829

Filter performance report

Filter Performance Analysis — Domestic Water Jug Filter

A paired influent and effluent analysis of a standard activated-carbon jug filter, challenged with the same Westminster mains water characterised in our tap water report.

Report number: EL-2026-04829
Date sampled: 04 August 2026, 09:05
Date received: 04 August 2026, 13:20
Date issued: 18 August 2026
Product tested: Domestic gravity jug filter, activated carbon and ion exchange cartridge
Cartridge state: New cartridge, conditioned per manufacturer instructions
Challenge water: Westminster, London SW1 mains supply (as report EL-2026-04817)
Throughput at sampling: 40 L (approximately 25% of stated cartridge life)
Protocol: Paired influent/effluent, triplicate filtration, mean reported
Temperature on receipt: 5.1 °C

Summary

The cartridge substantially reduced chlorine, chlorination by-products and lead, partially reduced PFAS and microplastics, and had limited effect on nitrate, fluoride and dissolved salts.

The same mains water characterised in report EL-2026-04817 was used as the challenge water, so influent values are directly comparable between the two reports. Free chlorine was reduced by 94.7% and total trihalomethanes by 80.6%, which is the expected behaviour of an activated-carbon medium and accounts for the change in taste and odour users report. Lead fell by 84.2% and copper by 79.0%, consistent with the ion-exchange component. PFAS reduction was partial: the sum of twenty compounds fell by 41.9%, with better performance on long-chain compounds such as PFOS and PFOA than on short-chain compounds such as PFBS. Microplastic particles were reduced by 78.6%. Nitrate, fluoride, sulphate and chloride were essentially unchanged, and hardness fell by 21.9% — enough to slow scale formation but not to soften the water. Microbiological indicators were absent in both influent and effluent; a carbon filter is not a disinfection device and colony counts at 22 °C rose slightly, which is normal for carbon media.

Free chlorine reduced 94.7%; total THMs reduced 80.6%
Lead reduced 84.2%; copper reduced 79.0%
PFAS sum reduced 41.9% — long-chain compounds outperform short-chain
Microplastics reduced 78.6% (1.4 → 0.3 particles/L)
Nitrate, fluoride, sulphate and chloride essentially unchanged
Hardness reduced 21.9%; not a disinfection device — colony count rose slightly

Chlorine

94.7%

Free chlorine reduction

THMs

80.6%

Total trihalomethane reduction

Lead

84.2%

Reduction from 1.9 µg/L

PFAS sum

41.9%

Partial reduction of 20-compound sum

Filter Performance Analysis — Domestic Water Jug Filter · Issued 18 August 2026Page 1 of 5

Independent water analysis · London

EL-2026-04829

Results

Influent values are the challenge water as supplied; filtered values are the mean of triplicate filtrations. Reduction is calculated from the paired means.

PFAS

7 parameters

Long-chain compounds are adsorbed more effectively than short-chain compounds.

Parameter	Unit	Influent	Filtered	Reduction	Method
PFOA	ng/L	3.1	1.4	54.8%	LC-MS/MS
PFOS	ng/L	2.4	0.9	62.5%	LC-MS/MS
PFHxS	ng/L	1.2	0.7	41.7%	LC-MS/MS
PFBS	ng/L	1.8	1.6	11.1%	LC-MS/MS
PFNA	ng/L	< 0.5	< 0.5	Not calculable	LC-MS/MS
PFHxA	ng/L	2.0	1.5	25.0%	LC-MS/MS
PFAS — sum of 20 compounds	ng/L	10.5	6.1	41.9%	LC-MS/MS

Metals and trace elements

11 parameters

Parameter	Unit	Influent	Filtered	Reduction	Method
Lead	µg/L	1.9	0.3	84.2%	ICP-MS
Copper	mg/L	0.081	0.017	79.0%	ICP-MS
Nickel	µg/L	2.6	0.9	65.4%	ICP-MS
Iron	µg/L	14	6	57.1%	ICP-MS
Manganese	µg/L	2.1	< 1	> 52%	ICP-MS
Arsenic	µg/L	0.7	0.6	14.3%	ICP-MS
Chromium	µg/L	0.6	< 0.5	Not calculable	ICP-MS
Cadmium	µg/L	< 0.1	< 0.1	Not calculable	ICP-MS
Mercury	µg/L	< 0.05	< 0.05	Not calculable	ICP-MS (CV)
Aluminium	µg/L	31	22	29.0%	ICP-MS
Sodium	mg/L	38	44	Increase (ion exchange)	ICP-OES

Filter Performance Analysis — Domestic Water Jug Filter · Issued 18 August 2026Page 2 of 5

Independent water analysis · London

EL-2026-04829

Microbiology

4 parameters

A carbon filter is not a disinfection device. Colony counts commonly rise across carbon media.

Parameter	Unit	Influent	Filtered	Reduction	Method
E. coli	cfu/100 mL	0	0	Not calculable	Membrane filtration
Total coliforms	cfu/100 mL	0	0	Not calculable	Membrane filtration
Enterococci	cfu/100 mL	0	0	Not calculable	Membrane filtration
Colony count, 22 °C	cfu/mL	4	26	Increase	Plate count

Inorganic chemistry

7 parameters

Parameter	Unit	Influent	Filtered	Reduction	Method
Nitrate	mg/L NO₃	24.6	23.9	2.8%	Ion chromatography
Nitrite	mg/L NO₂	< 0.02	< 0.02	Not calculable	Ion chromatography
Fluoride	mg/L	0.19	0.18	5.3%	Ion chromatography
Free chlorine	mg/L	0.38	0.02	94.7%	Colorimetry (DPD)
Total chlorine	mg/L	0.51	0.05	90.2%	Colorimetry (DPD)
Sulphate	mg/L	62	60	3.2%	Ion chromatography
Chloride	mg/L	48	47	2.1%	Ion chromatography

Volatile organics and pesticides

5 parameters

Parameter	Unit	Influent	Filtered	Reduction	Method
Total trihalomethanes (THMs)	µg/L	31	6.0	80.6%	GC-MS (headspace)
Chloroform	µg/L	24	4.6	80.8%	GC-MS (headspace)
Bromodichloromethane	µg/L	5.4	0.9	83.3%	GC-MS (headspace)
VOCs — 32 compound screen	µg/L	All < LOD	All < LOD	Not calculable	GC-MS (headspace)
Pesticides — 60 compound screen	µg/L	Metaldehyde 0.041	Metaldehyde 0.009	78.0%	LC-MS/MS

Filter Performance Analysis — Domestic Water Jug Filter · Issued 18 August 2026Page 3 of 5

Independent water analysis · London

EL-2026-04829

Microplastics

2 parameters

Parameter	Unit	Influent	Filtered	Reduction	Method
Microplastic particles, 20 – 500 µm	particles/L	1.4	0.3	78.6%	µ-FTIR after filtration
Dominant polymer identified	—	Polyethylene terephthalate	Polyethylene terephthalate	—	µ-FTIR

Physical properties

6 parameters

Parameter	Unit	Influent	Filtered	Reduction	Method
pH	pH units	7.6	7.4	—	Electrometric
Total hardness	mg/L CaCO₃	278	217	21.9%	ICP-OES (Ca, Mg)
Hardness (Clark degrees)	°Clark	19.5	15.2	21.9%	Calculated
Turbidity	NTU	0.21	0.09	57.1%	Nephelometric
Conductivity, 20 °C	µS/cm	684	641	6.3%	Electrometric
Total organic carbon	mg/L	1.6	0.5	68.8%	Combustion / NDIR

Filter Performance Analysis — Domestic Water Jug Filter · Issued 18 August 2026Page 4 of 5

Independent water analysis · London

EL-2026-04829

Technical observations

01
Reduction percentages are calculated from the paired influent and effluent means. Where the influent result was at or near the limit of detection, a percentage reduction cannot be calculated and is reported as such.
02
Sodium increased across the cartridge. This is expected behaviour for an ion-exchange medium, which releases sodium as it removes hardness ions and some metals.
03
Performance changes over cartridge life. This report characterises a cartridge at approximately 25% of its stated capacity; end-of-life performance is measured separately.
04
Results describe the single cartridge tested under the stated protocol and challenge water. They should not be read as a claim about all cartridges of this type.

Reading this report

Detection limits

Every parameter is reported with its limit of detection. A result below that limit is reported as “< LOD” and means the parameter was not measured above it.

Reference values

Where a UK statutory limit or recognised guideline exists it is shown alongside the result. Parameters without a health-based limit are marked informational.

Scope

Results relate solely to the sample as received and to the parameters listed. They are not a statement about the wider supply or about other units of the same product.

Authorised by

Technical Manager, London Water Testing

Testing & analysis

Testing managed by London Water Testing, London. Analysis performed by accredited specialist partner laboratories; the analysing laboratory and its accreditation status are stated on the issued report and are intentionally omitted from this illustrative sample.

Illustrative sample report

Values are modelled on published water-quality information for the Westminster supply zone and on typical performance ranges for domestic filters. This document demonstrates report layout and reporting conventions and is not the analysis of any specific property or product.

Filter Performance Analysis — Domestic Water Jug Filter · Issued 18 August 2026Page 5 of 5