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Will Horses Drink Bad Water? All You Need to Know.

Last updated: August 5, 2022

By: Miles HenryFact Checked

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The water in my horse’s drinking trough smelled like rotten eggs! Then I realized he had been avoiding the water there for quite some time, which really made me wonder if my horse could sense the water was spoiled and didn’t want to risk getting sick from it?

Horses will not drink bad water if it smells or tastes foul, but when contaminated with harmful substances without an abnormal taste or smell, horses may consume it, so be sure your horse’s watering buckets and troughs stay clean!

Many people believe that horses can distinguish safe drinking water from bad. But even though the horse does have a keen sense of smell and is very well-endowed with natural instincts, their senses don’t protect them from every hazardous substance in drinking water.

Picture of horses drinking water in the wild,

Do horses instinctively know not to drink toxic water?

I have often heard the saying, “Drink water from the spring where horses drink because they never drink bad water.” Does this mean that we can trust horses not to drink contaminated or toxic water, or should we be more careful?

A horse will instinctively know not to drink toxic water if the water’s not palatable and looks unclear. However, many toxic substances like blue-green algae often taste natural to the horse. Horses may also be wary of drinking unsafe TDS or pH levels depending on just how odd it tastes.

Just like humans, water is essential to a horse’s diet. Horses need water to effectively digest large amounts of fiber and maintain their body temperature, partly done through sweating. Most horses will drink five to ten gallons of water a day.

Horses are known for preferring to eat small amounts of grass throughout the day. This is why they need constant access to water so that their food can be digested properly and in turn cause no harm or discomfort to them while doing it.

Without a sufficient amount of water intake, horses could suffer from dehydration which may lead to more severe consequences such as kidney failure or colic– both being fatal conditions in extreme cases.

Because clean water is vital to their survival, horses have evolved to be very sensitive to the taste and smell of contaminants in their environment. Because of their sensitivity to the taste of water some horses are reluctant to drink any water that tastes or feels different, regardless of if it’s clean or not.

It’s also why it can be very frustrating to get them to drink water that doesn’t taste like home water. We might think it’s because horses aren’t thirsty, but that isn’t always true; sometimes, a horse just won’t drink anything other than what he or she knows already.

I like to use a simple trick when preparing horses for a long trip and lightly flavor their stable water with something like peppermint or apple juice. I use the same flavor at the new place we are visiting until the horses get comfortable with the local water.


Horses will drink bad water.

Sometimes, a horse will drink water even though it is contaminated. That’s because some toxic substances don’t smell or taste very dangerous. A good example is a water contaminated with blue-green algae.

Blue-green algae, or cyanobacteria, can cause the water to become highly poisonous to the horse – drinking even a few ounces can require a visit to the vet.

Water affected by blue-green algae may have an oily sheen and a tint of blue-green. However, the same visuals may be caused by some other, non-toxic substance. The only sure way to tell if the water is contaminated by harmful toxins is through lab tests.

Horses will often drink algae-contaminated water unabated. Blue-green algae are said to have an earthy smell, which is pretty normal if your horse is used to drinking water from natural sources.

How to check your horse’s water.

A good way to determine water quality is through the total dissolved solids (TDS) levels. TDS is the sum of all the inorganic and organic matter dissolved in the water. A TDS of less than 1,000 ppm (parts per million) is ideal for horse drinking water.

A TDS of 1,000 – 3,000 ppm is considered safe for horses but may cause mild diarrhea if the horse isn’t used to it. If the TDS is above 6,000 ppm, the water is not suitable for drinking, especially when caring for pregnant mares.

Sometimes, even small changes in TDS can be dangerous, depending on the specific substance. TDS changes generally cause a difference in the odor or taste of the water. If your horse refuses to drink water, it’s best to get the water tested for harmful substances at any agricultural or health lab.

Your horse might stop drinking the water if the “water hardness” is changed. Water hardness indicates the amount of calcium and magnesium present in the water. It can be caused if your community water source has been altered or if you move into a new region.

Hard water is generally safe for horses. If low sodium is a concern, consider supplementing their diet with a salt block.

Some picky horses might be reluctant to drink hard water, however. In that case, you can consult your vet and use a water softener before giving the water to your horse.

Water palatability for your horse also depends on the pH levels of the water. A pH range of 6 – 8.5 is generally safe for horses.

If the pH is too low or too high, it can mean that there are harmful elements or minerals in the water. Abnormal pH levels may be correlated with corrosion of plumbing in your house, scale buildup in water-related fixtures, or bad atmospheric conditions like pollution and chemical runoffs.

Horses will typically only refuse to drink acidic or alkaline water if it tastes or smells bad. If the horse can’t notice any foul texture in the water, it will continue drinking regardless of the water’s contents.

Not all horses are good at knowing when their water is bad. Particularly, dehydrated horses will drink just about any water they can find.

As a general rule, horses shouldn’t be given stagnant water, which has a funny color and might have feces, dead animals, or harmful fungi in it. If you suspect your horse’s water is bad, it’s best to change it get it tested from a lab.

Picture of a horse drinking green water from a pond,

Can horses drink green water?

Horses have a keen sense of smell, which they use to avoid drinking foul-smelling water. Though this may seem like an odd ability for such large animals, it is advantageous in the wild because that can make them more difficult prey and ensure their survival.

Green water is quite common in oceans. But what does it mean when your horse’s water supply turns green and is it a cause for concern?

Horses shouldn’t drink green water unless lab tests approve it. The green color can be caused by various harmful substances such as copper, dead plants, and algae. However, in some lakes and streams, green and other colors are caused by harmless suspended particles.

The color green is often associated with blue-green algae, which can release potent toxins into the water and make it unsafe for your horse. Green also might be more prevalent in decaying plant material found near rivers or streams containing stagnant pools of water.

If you have recently installed a new copper plumbing or copper has begun to leach into drinking water somehow, you might notice green or aqua stains in the water. Copper-contaminated water can be dangerous and shouldn’t be given to horses.

At the same time, not all green water is bad for horses. Many green algae are harmless and may only cause a slight change in the taste of the water.

Picture of horses in a pasture

How do you keep algae out of water?

Keeping algae out of the water trough is important for horse owners. Horses that ingest too much algae can become sick and refuse to drink-so it’s better not to make them suffer!

The thing you want to do is keep algae out of the water! Luckily, some easy ways don’t involve too much effort on your end. You can prevent algae from forming by keeping the container in a shady spot and checking for debris.

You should also make sure it’s always clean because if not, then bacteria will grow, which could potentially be harmful to your horse. Sometimes you may need to add chlorine, sulfates, or other special products, but only after consulting with a vet.

Ensure you secure water buckets high enough so that if a horse can’t accidentally defecate in it, this will contaminate the water, and algae have a greater chance of thriving due to the organic matter.

Similarly, try to make sure there are no dead animals or flies in the water when tending to your horse’s stall. Water buckets should also be adequately rinsed with bleach whenever you notice algae growth.

Adding barley straw to your horse’s water is also believed to prevent algae, though it’s not clearly understood why. The straw is only effective when applied before the appearance of algae. Depending on the temperature, it can take several weeks for the straw to prevent algae.

Can you put bleach in horse water?

When the weather is hot, it can be difficult to keep algae from growing in a horse’s water. Many horse owners choose bleach as an easy way to prevent this growth and avoid having their horses drink contaminated water that could make them sick or kill them if they ingest too much. While chlorine-based bleaches are not recommended for humans, is it safe for horses?

You can put bleach in a horse’s drinking water in small amounts. Don’t add more than one ounce of bleach to 50 gallons of water. Bleach contains chlorine, and too much chlorine is toxic to horses. Just like with humans, chlorine can have unintended consequences for the horse’s health, and large amounts can negatively interfere with the diet of horses.

Below is a YouTube video about the quality of the pond water horse’s drink.

YouTube video


Why would a horse not drink water?

A horse may not drink water for various reasons such as a physical blockage. Alternatively, there may be something in the water that’s preventing it from drinking. It could also possible be experiencing a medical condition such as colic or laminitis. Whatever is happening with your horse, please consult an equine vet right away!

How long can a horse go without drinking water?

Horses who have lacked access to drinking water only live 3 – 6 days before it becomes fatal. Horses deprived of water for two days begin to deteriorate quickly; on the other hand a horse deprived of feed is capable of surviving 20-25 with just an adequate supply of water.