By Better Living | Created at 2026-10-07 20:03:55 | Updated at 2026-10-07 21:48:55
3 hours ago
The cloudy water left after you boil potatoes can contain some of the starch and minerals released during boiling, so it’s fair to wonder whether you’re pouring something useful down the drain. These potato water uses range from low-concern to not recommended, and they all depend on one rule: the water must be cooked without salt. It’s the same save-the-liquid habit as rice water, but with a food safety catch you should know about first.
The short answer: the lowest-concern uses are watering plants and giving a pot a quick pre-soak, and both require water from potatoes boiled without salt, cooled completely. Using the water in soup or bread is a common kitchen habit, but Germany’s federal risk assessment institute advises against reusing potato cooking water for food at all. Salted water is for the drain.
It has to be unsalted. Salt in potato water is hard on plants, because salts build up in the soil and make it harder for roots to take up water. It also makes soup and bread dough easy to oversalt. If you season your potato water, pour it down the sink.
Two lower-concern potato water uses
1Water your plants, occasionally
Verdict: fine if it was unsalted and has fully cooled, but don’t expect a fertilizer. USDA’s Agricultural Research Service found that cubing potatoes before boiling reduced their mineral content by as much as 75 percent, which shows minerals are lost during boiling, and some of them end up in the water. We found no study showing that potato water gives houseplants a meaningful dose of nutrients. Our reading is that it’s unlikely to, so think of it as a reuse of water, not a plant food.
Salt is the real problem. Texas A&M AgriLife Extension’s soil salinity guide explains that plants struggle to draw water from salty soil, and Oregon State Extension lists brown leaf tips, wilting, dropped lower leaves and stunted growth as signs of salt buildup in houseplants. Let the water cool completely, use it promptly rather than storing it for days, use it only occasionally, and as a practical precaution don’t let it sit in the drip tray. If a plant gets salty water by mistake, the University of Maryland Extension suggests leaching with at least three times the pot’s volume of fresh water.
2Pre-soak a pot
Verdict: reasonable as a pre-soak, but not proven to clean better than warm water. If a pot is going into the sink anyway, a bit of cooled or warm unsalted potato water can loosen leftover food before you wash it. We found no research showing it cleans better than plain warm water, so treat this as a second use for the water, not a cleaning hack.
Two food uses the BfR advises against
Why these two come last. Germany’s Federal Institute for Risk Assessment (BfR) says consumers should not reuse the water in which potatoes have been boiled, because some of the glycoalkaloids (natural toxins in potatoes) can pass into it. Poison Control notes that cooking does not eliminate glycoalkaloids from green or sprouted potatoes, which is why our guide to whether potatoes go bad tells you to cut away or discard them. The BfR says normal potatoes usually contain 20 to 100 mg of glycoalkaloids per kg, and recommends table potatoes stay below 100 mg per kg. Because of this advice, we treat soup and bread as optional culinary habits, not recommended uses. If you are cooking potatoes for food, follow the BfR’s advice to use fresh, undamaged potatoes and avoid green or strongly sprouted ones, and don’t eat dishes that taste bitter.
3Thicken soup
Verdict: it can add a little body, but food safety guidance says not to reuse potato cooking water. When starch is heated in water, it swells and forms a gel, a process described by Science Meets Food, from the Institute of Food Technologists’ student association. Potato water can contain some starch, so a few spoonfuls of unsalted water might add body to a brothy soup. How much it holds varies, and we found no study measuring it, so treat it as a gentle boost at most. If you want a creamy texture, our guide to thickening soup without cream covers stronger options, including potato itself.
4Make softer bread
Verdict: a traditional baker’s habit, not established science, and subject to the same BfR advice. Swapping part of the water in a yeast dough for cooled, lukewarm, unsalted potato water is widely said to give a softer, moister loaf. We found no controlled study showing it. If you try it anyway, keep the water lukewarm so it doesn’t harm the yeast, and cut back the salt in the recipe.
How to save potato water
- Boil without salt. If you want seasoned potatoes, salt the dish afterward.
- Know the trade-off. The USDA finding above means cut potatoes give up more minerals to the water, and whole potatoes keep more of them in the potato.
- Cool it completely before use. Plants and yeast both need it at room temperature or cooler.
- Store it cautiously. The USDA says to refrigerate leftovers within 2 hours, using shallow containers to cool them quickly, and to use them within 3 to 4 days. For our purposes, use refrigerated potato water within 1 to 2 days. That is a more conservative window than the USDA’s general guidance for leftovers, which wasn’t written for potato water. Our guide to how long leftovers last has more.
- Throw it out if it smells off or the potatoes tasted bitter.
Potato water questions, answered
Is potato water safe to cook with?
Germany’s BfR advises consumers not to reuse potato boiling water because some glycoalkaloids can pass into it. We treat food uses as optional kitchen habits, not recommendations.
Can you use salted potato water on plants?
No. Salt can build up in the soil and stress plants, according to Texas A&M and Oregon State extension guidance. Use only water from potatoes boiled without salt, and let it cool.
Is potato water a good fertilizer?
We found no study showing it is. Minerals are lost into the water during boiling, but that doesn’t show that a houseplant gets a meaningful dose from it. Treat it as reused water, not plant food.
See also
Does potato water thicken soup?
A little, at most. It can contain some starch, but the amount varies and we found no study measuring it. The BfR also advises against reusing the water for food.
Does potato water make bread softer?
Bakers often say so, but it’s a tradition, not established science, and the BfR advice applies.
The bottom line
Potato water has two rules: it has to be unsalted, and it should come from fresh, undamaged potatoes. Plants and a quick pot pre-soak are the lowest-concern ways to reuse it, and neither is a big win. Soup and bread are common habits, but a German food safety agency advises against reusing the water for food, so we would skip them.
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