Winter water for horses: how much they need, and how to keep it open.

Published 23 October 2026

How much a horse drinks

eXtension puts the average adult horse at 10 to 12 gallons a day, which works out to about a gallon per 100 lb of bodyweight. Intake could easily double in hot, humid weather, and nursing mares often drink 20 to 25 gallons. eXtension adds that adequate water matters as much in winter as in summer: horses can handle severe weather if they have adequate forage and plenty of water to process it.

Montana State Extension gives lower numbers: adult horses normally drink 5 to 8 gallons, rising to 9 to 10 gallons as hay increases in cold weather. The sources differ, so plan tanks at the top of the range. Running short is the costlier mistake.

For a tank, divide its capacity by the herd’s daily need. A 100-gallon tank serving four horses at 12 gallons each lasts a little over two days (100 ÷ 48 = 2.1). That is simple arithmetic, not a published figure.

Why cold water is the problem

eXtension says horses prefer water at 45 to 65°F and avoid water that is too hot or too cold. At 32°F a 1,100 lb horse may drink as little as 1 to 3 gallons a day. Against the 10 to 12 gallons it normally needs, that is roughly 10 to 30 percent of normal (my arithmetic).

The risk is spelled out by both sources. eXtension: “Low water intake is directly related to the increased incidence of impaction colic.” Montana State: impaction colic can be caused by eating hay and not consuming enough water, and hay-based diets raise water needs. Winter is when both things happen together.

Snow does not cover the gap. eXtension says snow or a frozen pond does not supply enough water.

Keeping it open and warm

• Use a heater. Montana State recommends water heaters to prevent freezing or overly cold water, and eXtension notes that small heaters can be used in box stalls to keep water from freezing.
• No heater? Check twice a day. Montana State says to check water sources twice daily and remove ice. eXtension says to break and remove ice so water stays available free-choice.
• Offer warm water if you can. eXtension suggests 10 gallons at 65°F or warmer, twice daily, where possible.
• Get hay in before the cold. eXtension says to raise the diet’s dry matter 24 hours before forecast cold, and that water intake can be encouraged by feeding more forage before a drop in temperature.
• If you feed a concentrate, mash it. When water is below 45°F, eXtension suggests adding 2 to 3 gallons of hot water to a textured or pelleted concentrate each day and letting it sit 15 minutes before feeding, which it says reduces gas colic risk.

Any electric heater in a trough should be installed by someone qualified. The sources I read do not cover heater specifications.

Where the trough goes

On a dry lot, eXtension puts the water at the opposite end from the shelter, which encourages horses to move and limits erosion around the trough. It also recommends frequent cleaning to keep out manure and other debris and to stop algae and bacteria building up, though it gives no schedule.

Hay is the other half of this. The hay guide covers how much to buy, and the hay shortage guide covers how to stretch it. More hay in the ration means more water to go with it.

What these sources do not settle

The gallon figures differ between sources, from Montana State’s 5 to 8 up to eXtension’s 10 to 12, so treat them as a planning range and watch your own horses. Neither gives tank sizes or heater specifications.

You may see a figure that heated water raises intake by about 40 percent, attributed to a University of Pennsylvania study. I could not open that study, so it is not used here.

If a horse stops drinking or shows signs of colic, call your vet.