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Kirkland Signature (Costco) Purified

Costco's Kirkland Signature bottled water is made by Niagara Bottling; Niagara's report covers it as purified water with minerals added for taste. — as described by the brand

8.4/10Waterphile Score8/9 properties published

pH6.69 ideal 6.5–8.59.3
TDS31.64 mg/L ideal 225–500 mg/L5.0
Sodium2.36 mg/L ideal up to 20 mg/L10.0
Calcium2.79 mg/L ideal 36.7–80 mg/L · counts half5.0
Magnesium0.1 mg/L ideal 16.7–30 mg/L · counts half5.0
SulfateND mg/L ideal up to 248 mg/L10.0
Chloride6.69 mg/L ideal up to 250 mg/L10.0
NitrateND mg/L as N ideal up to 10 mg/L10.0
BicarbonateNot published −0.1—

Each bar is out of 10 for that property. Deductions: −0.1 for missing values. Editorial score, not a health rating. How scores work →

Mineral FactsPer litre · 8 of 11 values published

Basics

Total dissolved solids TDS

31.64 mg/L

Minerals

Calcium

2.79 mg/L

Magnesium

0.1 mg/L

Sodium

2.36 mg/L

Potassium

5.26 mg/L

Other dissolved substances

Bicarbonate

Sulfate

Not detected

Chloride

6.69 mg/L

Nitrate (NO₃)

Not detected as N

Silica

— Not published by the brand · we never estimateSource: Niagara Bottling Water Quality Report 2026, 'Purified Water with Minerals added for Taste' column · checked 2026-10-25

Source kind: bottler report (Niagara Bottling). Kirkland Signature has no separate report; Consumer Reports files the Niagara 'Purified With Minerals Added' report under Kirkland (https://article.images.consumerreports.org/image/upload/prod/pdf/cq_water_reports/Kirkland_Springs_Costco_2018_Purified_With_Minerals_Added.pdf). Check the bottle for the bottler; Kirkland spring water variants are not covered. On 2026-10-25 the PDF returned 404 to our fetcher; values were read from the Internet Archive copy of the same URL. Alkalinity is published only as CaCO3, so bicarbonate is left empty. Silica not published.

How it stands out

Lowest tds of the 54 brands that publish a tds value (31.64 mg/L).
Sodium is 2.36 mg/L, under the 20 mg/L level the UK/EU uses for “suitable for a low-sodium diet” on natural mineral water labels.

UK/EU label thresholds met

Applied to the published numbers for information; these indications legally apply to natural mineral water labels.

Suitable for a low-sodium diet (sodium < 20 mg/L)

Taste notes

No taste notes yet. Soon you will be able to say how Kirkland Signature (Costco) Purified tastes to you. Results will appear here once people have voted; nothing is shown until then.

SoftNo votes
CrispNo votes
SmoothNo votes
MineralNo votes
SaltyNo votes
SweetNo votes
BitterNo votes
MetallicNo votes

Ratings & reviews

Be the first to rate Kirkland Signature (Costco) Purified. Not rated yet, and no reviews yet. Ratings and reviews are not open yet; we will never show made-up scores.

Similar waters

Computed from published numbers only: the waters whose mineral values are closest to Kirkland Signature (Costco) Purified’s on a log scale, using the values both brands publish as single numbers (at least 5). pH and nitrate are not used. Similar minerals do not mean similar taste.

Source & spring

Source	Niagara Bottling plants (varies by plant)
Country	USA · all waters from the USA
Water type	Purified water · what this means
US label wording	Purified water with minerals added for taste (report wording)
Still or sparkling	Still
Data source	Niagara Bottling Water Quality Report 2026, 'Purified Water with Minerals added for Taste' column Last checked 2026-10-25

Brands update their analyses from time to time, and values can differ between bottle sizes, plants and batches. Check the label on your bottle. Spotted a change? See corrections.

Where to buy

See the official Kirkland Signature (Costco) Purified website for stockists. Retailer and price links are coming later.

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Not medical advice. Waterphile shows mineral values as published by each brand, for general information only. If you have a health condition, follow a restricted diet or prepare infant formula, ask a doctor, pediatrician or health visitor.