Horses drink a lot of water! Horses are around 7 times heavier than us, so we know they are going to drink more water than us. Whilst the typical water intake for a 70kg adult is 1-3 litres per day. This can increase with physical activity, in hot weather and with high salt and or protein intake. For a 500kg horse this is likely to be around 25 litres per day. And with exercise and warm weather this may be as high as 70 litres per day (nearly 5 x 15 litre buckets).
If you rely on mains water it could be a significant cost and with water bills set to go up significantly this year, it’s likely that a lot more horse owners may consider collecting rainwater for their horses instead of using mains water. In the wild, horses and ponies clearly survive by drinking from ponds, lakes, streams and rivers, which of course are all fed from rainwater.
When Is Rainwater Safe for Horses?
Fresh rainwater is generally safe for horses to drink, especially when it falls directly into clean troughs, buckets, or natural water sources. Many horses living in pastures naturally consume rainwater without any issues. As long as it is free from contaminants, rainwater can be a suitable and cost-effective source of hydration.
Potential Risks of Rainwater
While rainwater is often safe, there are several factors that horse owners should consider to reduce potential health risks:
- Stagnant Water Issues: If rainwater sits in a trough, bucket, or tank for too long, it can become a breeding ground for bacteria, parasites, and algae, which can be harmful to horses.
- Contamination from Storage Methods: If rainwater is collected from a roof, gutter system, or open tank, it may contain dirt, bird droppings, leaves, or chemicals that could make it unsafe.
- Algae Growth: Warm temperatures and stagnant conditions can promote algae growth, particularly blue-green algae, which can be toxic to horses.
- Acid Rain or Pollutants: In urban or industrial areas, rainwater may carry pollutants that alter its pH, potentially making it less desirable for consumption.
Signs That Your Rainwater May Be Contaminated
Gastrointestinal symptoms
- Diarrhoea or loose droppings – A common symptom of bacterial, parasitic, or chemical contamination.
- Colic symptoms – Signs like restlessness, pawing, rolling, or loss of appetite could indicate gastrointestinal irritation.
- Excessive thirst or refusal to drink – Horses may instinctively avoid water that smells or tastes bad, or they might drink more if dehydrated due to illness.
Neurological Symptoms (Toxicity from algae, heavy metals, or chemicals)
- Muscle tremors or weakness
- Uncoordinated movements (ataxia)
- Seizures (in severe cases, particularly from toxic blue-green algae exposure)
- Lethargy or depression
Skin and Coat Changes (Possible chemical exposure or bacterial contamination)
- Skin irritation or sores – Especially if rainwater contains pollutants, heavy metals, or mould.
- Dull coat or excessive shedding – Could indicate prolonged exposure to harmful substances affecting overall health.
Respiratory Issues (If the water contains fungal spores or mould)
- Coughing or nasal discharge
- Difficulty breathing (severe cases)
Signs of Poisoning or Organ Damage (Long-term exposure to toxins like pesticides, heavy metals, or industrial runoff)
- Weight loss despite normal eating habits
- Jaundice (yellowing of gums/eyes) – Possible liver damage from toxins.
- Dark or reddish urine – Potential kidney or liver problems.
Immediate Actions to Take If You Suspect Your Rainwater May Be Contaminated
✅ Stop providing the rainwater
✅ Provide clean, fresh water immediately to encourage hydration.
✅ Observe symptoms and behaviour closely for any worsening.
✅ Contact your vet if symptoms persist or worsen.
✅ Test the water source for bacteria, algae, heavy metals, or chemicals.
How to Ensure Rainwater Is Safe for Horses
To keep rainwater safe and clean, horse owners should take the following precautions.
- Regularly Clean Troughs and Containers – Wash out water troughs and buckets frequently to prevent debris buildup, algae formation, and bacterial growth.
- Use Covered Storage Tanks – If collecting rainwater, use a covered storage system with proper filtration to keep contaminants out.
- Monitor Water Quality – Regularly check rainwater for unusual odours, discoloration, or floating debris. If the water appears green or cloudy, it may contain algae or bacteria and should be replaced.
- Provide an Alternative Water Source – Always ensure horses have access to a clean, fresh water source, such as well water or tap water, in case the rainwater becomes unsuitable.
- Position Water Sources Properly – Avoid placing troughs under trees or in areas where bird droppings and leaves could easily contaminate the water.
How to test your water and what to look for:
There are many test kits for water quality available online. Some of the important things to test for are as follows.
- Total Dissolved Solids (TDS): The safe upper limit for horses is 6,500 mg/l. Water with less than 1,500 mg/l TDS is considered fresh water.
- pH: The ideal range is 6.5 to 8.5
- Nitrates: Water with less than 400 mg/l of nitrate is generally safe. Water with more than 1500 mg/l of nitrate may be toxic. Nitrates are naturally occurring and soluble, so ponds and shallow wells near fertilised fields can have high nitrate levels.
- Faecal coliforms: These bacteria are commonly found in the intestines of warm-blooded animals. Their presence in water indicates recent faecal contamination.
- Algae: Blue-green algae (cyanobacteria) blooms are very dangerous for horses
Bottom Line
Horses can drink rainwater, and in many cases, it is a natural and safe hydration source. However, to maintain their health and well-being, owners should take steps to ensure the water remains clean and free from contaminants. By monitoring water quality, regularly cleaning troughs, and providing alternative freshwater sources, horse owners can confidently allow their horses to drink rainwater without concern. By following these simple precautions, you can make rainwater a reliable and healthy hydration option for your horses all year round – provided it rains enough!
