Can My Pet Drink From Puddles and Streams?

Hot day with dog. Thirsty yellow labrador retriever drinking water from the plastic bottle his owner.

As the summer starts to heat up and our pups pant the day away, be alert to their hydration and sources of water. Dogs regulate their temperature mainly through evaporative heat transfer/cooling via their lungs. Unlike people they do not have very active sweat glands. Panting releases a substantial amount of water vapor from the body, so drinking water frequently is a necessity, especially when it’s hot.

When out for a stroll in the woods, is it safe to permit your dog to drink water from puddles and streams? Maybe. Unlike their wild ancestors, our domestic dogs aren’t as prepared for the normal bacteria and parasites in natural water sources. The more stagnant the water, the higher the degree of concern. Flowing water tends to have less toxins and a lower bacteria and parasite count. Playing it safe by bringing water from a clean source.

Potential risks / concerns with water from untreated sources include:


In a recent article, we discussed this common bacteria, which is passed in the urine of mammals, including rats, raccoons, skunks, etc. Infection with the leptospirosis bacteria can lead to liver and kidney failure. This bacteria is also transmissible to people. Leptospirosis is found here in the city and also in the suburbs/rural areas. Puddles are of main concern. Clinical signs may include fever, vomiting, lethargy, diarrhea, and muscle pain or weakness.


Common in puppies, giardia is a leading cause of diarrhea. This bug is a protozoal parasite, which may be difficult to eliminate, frequently requiring two medications. It too is water-borne, and is passed from animal to animal via fecal contamination. Dogs with giardia may experience watery diarrhea (or sometimes none at all), vomiting, weight loss, lack of appetite and lethargy.


Cryptosporidiosis, like giardia, has a protozoal causative agent. While carried by most mammals, it is most commonly found in more rural areas near farmland. It may cause intractable watery diarrhea, dehydration, and is quite nasty. Don’t ask how I personally know this.

Escherichia Coli

E. coli, for short, is a very common bacterium found in most mammals. It usually does not cause clinical disease in small numbers, but some virulent strains may lead to vomiting and diarrhea, similar to giardia. Like giardia, E. coli is passed from animal to animal from water contaminated with feces.

Cyanobacateria (Blue-Green Algae)

Found in most water sources, most cyanobacteria are harmless. Toxic strains may be found in ponds and lakes, less commonly in flowing water. This bacteria can rapidly multiply under the right conditions, leading to high levels of contamination. Ingestion can lead to vomiting, liver failure, seizures, and frequently, death. Progression of signs can be quite rapid.  Avoid swimming, drinking, and contact with any water that has visible pond scum, a greenish or bluish sheen, or large amounts of algae present.


Although not winter, combustion engine vehicles will all have antifreeze in their radiators. The main ingredient is ethylene glycol, which tastes sweet. Dogs will lick it off pavement or from puddles on roadways. Ingestion may cause irreversible kidney failure and neurologic disease.

Moral of the story: When out with your dog on an adventure, bring fresh water. And most definitely avoid stagnant ponds and streams.

Dan Teich, DVM, is medical director at District Veterinary Hospitals at Eastern Market and Navy Yard