During years of rain, water is abundant on the Appalachian Trail. However, some water sources can become contaminated with microscopic bacteria and protozoa like giardia. For this reason, it’s necessary to carry a system for purifying your water. Below are tips for locating the best sources of water and ways to purify water.

A hiker getting spring water

Where to Find Water

  • Most shelters are built near water sources that are clearly marked. A notable exception is the Mashipacong Shelter in NJ.
  • Your guidebook (e.g. The A.T. Guide) contains locations of water sources along the trail. Take note of these spots before starting out in the morning.
  • Springs, especially when they are bubbling, are the best sources of water. Sometimes, caretakers will place a pipe in the spring so hikers can collect water more easily.

    Hikers filtering spring water

  • Streams are the next best source of water. Select streams that are small and flowing rather than stagnant.
  • Rivers are not an ideal source for water because they can contain contaminants from places farther up the river.
  • Ponds/Lakes are not ideal as well, especially if they are used for recreation. Additionally, a lot of lakes smell fishy. Sometimes, your only option is a pond or a lake. In Maine, a lot of the shelters’ water sources will be the nearby ponds. Luckily, many of these are isolated from human populations but contamination from other animals is still a concern.

    A hiker filtering pond water

  • Water sources that are located in lower elevation regions have the greatest chance of having contaminates from runoff of roads, sewers, and farmlands. Try to get your water while up in the mountains. If you have limited options, try to draw water from small sources rather than large sources like a lake.

Giardia, A Common Illness on the Trail

Giardia (gee-ahr-dee-ah) is a common ailment of AT hikers who don’t purify or improperly purify their water. It’s an infection of the small intestines caused by an organism found in raw sewage.

The symptoms of giardia are abdominal pain, diarrhea, gas, bloating, headache, loss of appetite, low-grade fever, nausea, swollen abdomen, and vomiting.

If struck with giardia, it’s important to drink plenty of liquids to prevent dehydration and seek medical treatment immediately.

Ways to Purify Water

  • Drops, like Aquamira, are used by many thru-hikers. It’s a good backup to carry just in case your filter doesn’t work. Liquid bleach has also been used by thru-hikers. Bleach is not recommended for long term use, but it can serve as a good backup. Iodine isn’t effective against a common protozoa, cryptosporidium, so it’s not recommended.
  • Pump filters, like the Katadyn Hiker Pro and MSR Miniworks EX, are relatively heavy (11 oz – 1 lb) but effective. Pump filters need to be cleaned especially when water contains a high level of particulates.
  • Ultraviolet light devices, like the SteriPEN, are effective at killing bacteria. However, thru-hikers have reported it failing on the trail. With any system, you should have a backup.
  • Boiling water to a rolling boil is fine if you are going to cook with it anyway. Otherwise, don’t waste fuel in order to purify your water, and use another system instead.

Other Tips

  • After using purification drops or a SteriPEN, remember to clean the threads of your bottle. Turn the bottle upside-down and open the cap a little to let the water run out of the opening to clean it from contaminants.
  • For Northbounders, sparkling springs become more scare past Pennsylvania. In some areas, you might have to draw from stagnant sources. For this reason, individuals might consider using a water pump when getting past Pennsylvania.
  • Read your manuals carefully and test your equipment before getting onto the trail.
  • Before hiking, some hikers ask their doctor for a prescription for an antibiotic for traveler’s diarrhea and then fill it before starting out.