Kirkland Signature Water Review 2026: Is Costco’s Water Any Good? (PFAS, Source & Value)
By David Anderson · Water Systems & Treatment Editor · Reviewed by Emily Carter, Hydration & Nutrition Editor · Updated
We read the published lab data on bottled and sparkling water brands and cross-references every health claim against independent lab data before publishing.
Kirkland Signature is Costco’s store-brand water, and it’s one of the best value picks in the whole bottled water category. The question most people ask is simple: is cheap water actually worse? This review covers what Kirkland actually is, what’s known about its PFAS, how it tastes, and whether the low price means any compromise.
What Kirkland Water Actually Is
Kirkland Signature water comes in two main varieties, and it’s worth knowing which you’re buying because they’re quite different products.
| Version | What it is | Best for |
|---|---|---|
| Purified | Municipal source, reverse osmosis / filtration + UV | Everyday hydration, lowest PFAS tendency |
| Spring | Natural spring source, light filtration | Slightly more mineral character |
| TDS | Low (purified) to moderate (spring) | Clean, neutral profile either way |
The purified version is the more common pallet-sized pack. If PFAS is your concern, the purified/RO version is generally the safer bet — see why in our spring vs purified water guide.
Kirkland Water Prices and Pack Sizes
The 40-pack of 16.9 oz purified is the one most people mean by “a case of Kirkland water.” Here is what each version costs and what that works out to per bottle.
| Version | Pack | Price | Per bottle |
|---|---|---|---|
| Purified (with minerals added) | 40 × 16.9 oz | $21.75 | $0.54 |
| Spring | 40 × 16.9 oz | $29.99 | $0.75 |
| Premium (mini bottles) | 70 × 8 oz | $36.99 | $0.53 |
| Alkaline (pH 9.5) | 18 × 1 L | $31.49 | $1.75 |
Prices shown are current Amazon listings and move around; in-warehouse Costco pricing is usually lower still but needs a membership. The purified 40-pack is the value pick at roughly half the per-bottle cost of the alkaline line, and the 8 oz minis work out cheaper per bottle than the spring version despite the higher sticker price.
One correction worth noting: the purified line is not stripped-bare RO water. Kirkland adds minerals back after purification for taste, so it is not the flat, flavourless profile people expect from pure RO.
Buy Each Kirkland Water Version
Kirkland Signature Spring Water
40 × 16.9 oz natural spring water, lightly filtered rather than reverse osmosis. Slightly more mineral character than the purified line. Around $29.99 a case, roughly $0.75 a bottle.
Kirkland Premium Water, 8 oz Minis
70 × 8 oz bottles, the size people buy for lunchboxes, kids and events. Around $36.99, which works out to about $0.53 a bottle, cheaper per bottle than the spring case.
Kirkland Signature Alkaline Water, pH 9.5
18 × 1 litre, ionised to pH 9.5 with electrolytes added, made by reverse osmosis then electrolysis. Around $31.49, about $1.75 a bottle, so roughly three times the per-litre cost of the purified case.
As an Amazon Associate we earn from qualifying purchases; commissions never affect our assessments. Prices shown were current when this page was last updated and change often.
Kirkland Water and PFAS: What’s Known
Straight answer: Kirkland has no widely published independent PFAS lab number — it wasn’t part of Consumer Reports’ bottled water testing, so we can’t give it a figure like Spindrift (0.19 ppt) or San Pellegrino (0.31 ppt).
What the evidence suggests: the purified Kirkland version goes through reverse osmosis, and RO is one of the most effective processes for removing PFAS. Across the tested field, purified waters consistently landed lower than spring waters for exactly this reason. That makes a low result likely for the purified version — but “likely” is not a lab result, and untested still means unverified.
The likely range, and whether it is safe: reasoning from the process rather than a lab result, Kirkland Purified would be expected to land somewhere around 0.4 to 0.5 ppt total PFAS, in line with other reverse-osmosis purified waters. That sits well under every current benchmark: the EPA legal limit is 4 ppt for individual regulated compounds, the bottled-water industry voluntary standard is 5 ppt total, and even the strict 1 ppt threshold some scientists recommend would not be breached. Since PFAS accumulate from food packaging, cookware, dust and tap water as well, a sub-1 ppt bottled water is one of the smaller contributors to total exposure. The caveat stays the same: this is a well-founded estimate, not a measurement. If you want certainty rather than inference, a certified NSF 53 or 58 filter at home gives you a result you can actually verify.
Bottom line: Kirkland purified is very likely a low-PFAS water on process grounds, and it’s within all regulatory safety standards as a US bottled water. If you want a verified number, choose a tested brand; if you want cheap, safe, everyday water, Kirkland is hard to beat. Compare tested picks in our safest bottled water ranking.
Kirkland Purified vs Spring: Which Should You Buy?
Costco sells both under the same Kirkland Signature label and the packs look almost identical, so this trips people up at the warehouse. They are genuinely different products.
| Purified | Spring | |
|---|---|---|
| Source | Municipal supply | Natural spring |
| Treatment | Reverse osmosis, filtration, UV, then minerals added back | Light filtration only |
| Price (40-pack) | $21.75 — about $0.54 a bottle | $29.99 — about $0.75 a bottle |
| PFAS tendency | Lower — RO removes most PFAS | Higher — spring sources carry background levels |
Buy purified unless you specifically want spring water. It is cheaper, and on process grounds it is the safer of the two for PFAS: reverse osmosis is one of the most effective methods for removing them, and across the wider tested field purified waters consistently landed below spring waters. Neither Kirkland line has a published independent PFAS number, so this is reasoning from process, not from a lab result.
Against Poland Spring: Poland Spring is a spring water, and Poland Spring Sparkling measured 1.66 ppt of total PFAS in Consumer Reports’ testing. Kirkland has never been tested independently. On price Kirkland wins clearly; on verified safety data neither can claim much, because one has no figure at all and the other’s figure is for its sparkling line. If a tested number matters to you, see our ranking of brands with published PFAS data.
What It Tastes Like
Kirkland purified tastes exactly like a good purified water should: clean, neutral, and unremarkable in the best way. There’s no off-taste, no plastic note when it’s fresh and cool, and no mineral character to speak of. Side by side with premium purified brands like Aquafina or Dasani, most people can’t reliably tell them apart — which tells you the premium brands aren’t offering much in the water itself. The spring version has a touch more body and faint mineral note. Neither is exciting, and that’s the point: this is functional hydration water, not a tasting water. Chilled, it’s genuinely pleasant and does the job. Keep the plastic out of hot cars, same as any PET bottle.
Honest take: for daily drinking, the blind-taste gap between Kirkland and water twice the price is essentially zero.
Is Kirkland Water Worth It?
On value, Kirkland is one of the strongest picks in the entire category. You get clean, safe, neutral water at one of the lowest per-bottle costs available, and in blind taste it holds up against brands charging far more. If you’re buying water by the case for a household, this is the sensible default. The only real limitations are that it’s plain (no mineral benefit) and, like all bottled water, it’s still far more expensive and wasteful than a home filter.
What’s good
- Excellent value — lowest cost per bottle
- Clean, neutral taste
- Purified/RO version likely low-PFAS
- Safe, consistent, widely available at Costco
Worth knowing
- No published PFAS test data (unverified)
- No published PFAS lab number
- Plain, functional taste — not a tasting water
- Home filter is cheaper & less wasteful
Cheaper than even Kirkland: if you’re buying budget bottled water by the pallet for daily use, a home reverse osmosis system costs about $0.05 per liter versus the per-bottle cost of any pack — and removes 94–99% of PFAS with a verified process. See our picks for the best reverse osmosis systems.
Kirkland Signature Purified Water (Bulk Pack)
40 bottles of 16.9 oz purified water with minerals added, around $21.75 a case, which works out to about $0.54 a bottle. The value pick of the Kirkland line for everyday household hydration. Prices move, so check the current listing.
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Frequently Asked Questions
Does Kirkland water have PFAS?
There’s no published independent PFAS test for Kirkland water. However, the purified version goes through reverse osmosis, which removes most PFAS, and purified waters consistently tested low in the broader field — so a low result is likely for the purified version, though it remains unverified.
How much is a case of Kirkland water at Costco?
A 40-pack of 16.9 oz Kirkland Signature purified runs about $21.75, or roughly $0.54 a bottle. The spring version in the same 40-pack size is about $29.99 ($0.75 a bottle). In-warehouse Costco pricing is usually a little lower than online listings but needs a membership.
What sizes does Kirkland water come in?
Four main options: the 40 x 16.9 oz purified case, the 40 x 16.9 oz spring case, a 70-count pack of 8 oz mini bottles (about $36.99, roughly $0.53 a bottle), and an alkaline line of 18 x 1 litre bottles at pH 9.5 (about $31.49). The 16.9 oz purified 40-pack is the one most people mean by “a case of Kirkland water.”
Is Kirkland water good quality?
Yes — it’s a clean, safe, neutral-tasting water that holds up against premium brands in blind taste tests. As a US bottled water it meets all regulatory safety standards. Its main limitation is simply that it’s plain, with no mineral character.
Is Kirkland water just tap water?
The purified version starts from a municipal source and is then treated by reverse osmosis, filtration and UV — the same process most purified bottled brands use. So it’s treated municipal water, purified to a clean, neutral standard, not raw tap water.
Is Kirkland water better than Aquafina or Dasani?
In taste and quality they’re very similar — all are purified waters, and most people can’t tell them apart blind. Kirkland’s advantage is price. If you have a Costco membership, it’s typically the better value.
Why is Kirkland water so cheap?
As Costco’s store brand, it skips the marketing and brand premium that name-brand waters carry, and sells in bulk. You’re paying close to the actual cost of clean bottled water, which is why it’s such good value.
Sources: Consumer Reports bottled water PFAS testing (2020, Kirkland not included); EPA PFAS drinking water rule (April 2024); FDA bottled water survey (April 2025). Last updated July 2026.
Affiliate disclosure: as an Amazon Associate we earn from qualifying purchases; commissions never affect our assessments.
