Which Type of Water Tastes Best in Whiskey?

Whether or not you add water to whiskey defines you as a whiskey drinker. While many dedicated whiskey drinkers are firmly opposed to “diluting” a glass of neat whiskey, others believe that adding a few drops of water to a dram opens up its flavors and aromas. This theory inspired companies in Scotland and Kentucky to market waters specifically designed to mix with bourbon and scotch.

The thinking is that the best water for a particular whiskey is one that comes from the same source as that whiskey. While that logic makes sense, we were still skeptical. It got us thinking: Does the type of water you dash into your whiskey actually make a difference? We decided to set up an experiment.

We tested eight different waters (five specialty waters, three readily available options), tasting each on its own and splashed into a standard overproof whiskey, to find out exactly how each water affected the spirit’s aroma and flavor. Here’s what happened.

Disclaimer: We did not taste each of the specialty waters with the particular whiskeys for which they were designed. The results of this test should be taken as general tasting notes and not as a reflection of the precise purpose or effectiveness of these waters.

Unfiltered NYC Tap Water

New York City’s tap water has been lauded as some of the best in the nation, and we can attest to its mild flavor and smooth mouthfeel compared with tap water from, say, Kansas (this particular writer’s home state). Its pH is about 7.2—just slightly above what is considered neutral. On its own, the flavor is clean with mild minerality. But in whiskey, the tap water did little to enhance the flavor. It softened the blow of the ethanol at first sip, but didn’t bring forward or open up any of the sweeter or warmer tones in the whiskey.

Distilled Water

The pH of distilled water is supposedly about the same as that of tap water, although various tests on the subject have proven otherwise, including one done by spirits writer Camper English who measured it coming in at a pH of 5.6. With only our tongues to judge, we found that it didn’t have much flavor one way or the other. The distilled water softened the whiskey on the palate a little better than the tap water, but didn’t do much to open up or alter the flavor.

Evian Natural Spring Water

We found this bottled water to be fairly similar to tap water. It’s light on the palate and faintly chalky with a pH of 7.4. In the whiskey, it mellowed the spice and started to round out the spirit’s sweet notes. But it also imparted some minerality to the dram.

Uisge Source Islay

Each bottling of Uisge Source is meant to complement a different variety of scotch. This one, which is sourced from the Ardilistry Spring, is meant to pair well with Islay whisky. These whiskies often have a smokier character, thanks to the peated barley process, and this water shares some of those qualities. When sipped by itself it has a mild earthy flavor. The brand doesn’t disclose the exact pH levels of each of its waters on its website, though it does indicate that the water comes in close to a pH of 6, and attributes this higher acidity to its natural peat filtration. When added to whiskey, it tamed the ethanol flavors, rounding it out and enhancing the rich, leathery notes of the whiskey. We were pretty impressed with this particular water’s ability to improve the overall flavor.

Uisge Source Speyside

If we had to choose any of Uisge Source’s waters to sip on a daily basis, we’d pick this one. It’s low in minerality with a silky texture, coming in closer to 8 on the pH scale. Its smooth and stoney flavor can be attributed to its origins: the Cairngorms Well in the Speyside region of Scotland. The water naturally filters through hard rock, including granite. Though we loved it straight, it did not open the whisky up as much as we were hoping. Perhaps our overproof whisky was too much for it. We found its effects quite similar to that of the tap water.

Uisge Source Highland

As its name suggests, this water—and the variety of scotch it’s meant to complement—hails from the northern region of Scotland. It’s sourced from St. Colman’s Well in Ross-shire and is supposedly very similar to the water used by the region’s distilleries. On its own, it has a light minerality and a slight stoniness, thanks to the sandstone and limestone through which it naturally flows. When added to whiskey, the flavors remained largely unchanged.

Franklin & Sons Ltd. Scottish Artesian Water

This Scottish Highlands-sourced water—which comes from the springs near Balmoral Castle in the Cairngorms National Park—breaks everything down right on the label, from the calcium, magnesium and chloride content of the water to the pH at source, which comes in at 6.1. It has a softer minerality than Uisge’s Highland water, though it’s noticeably more mineral-heavy than distilled water. Rather than relegating itself to one type of whisky, Franklin & Sons claims it helps “release the true character of the finest spirits.” A splash of this water in whisky enhanced the whisky’s natural sweetness and smoothed the flavor significantly more than the other Highland water as well as the other more widely available waters.

Old Limestone Mixing Water

The term “branch water” or “bourbon and branch” comes from an old Southern tradition of serving Kentucky bourbon with fresh spring water. That’s the basic idea behind Old Limestone’s water, which is bottled with a pH of 5.6. Sipped straight, the limestone flavor shines through. In a glass of whiskey, Old Limestone helped to round out and soften the flavors, seemingly without altering its flavor, but bringing some of the sweeter caramel flavors to the forefront.

The Verdict

The type of water you splash into your whiskey really does make a difference. We were surprised by the extreme differences between each of the waters in this tasting, both on their own and in the whiskey. The specialty waters that shared some of the whiskey’s characteristics definitely helped the whiskey open up, so it seems these potentially gimmicky products are actually delivering on their promise. We also noticed that we tended to favor the waters with a lower pH.

The bottom line: If we had to choose a water to pair with our whiskey, we’d certainly prefer to use one from the region in which the whiskey was made—but we also wouldn’t turn our nose up at tap or bottled water. As long as the whiskey’s good, we’re good.