When wilderness camping, hiking and canoeing for more than a day it is not practical to carry enough drinkable water to meet your needs. Often it is necessary to obtain drinking water from a lake, river pond or any available source of water. All water that you drink unless it is rain water, melted snow or dew must be purified to rid it of dangerous bacteria and micro organisms like giardia. This must be done by either boiling or filtering the water.
Several filters are available that make the job of obtaining purified drinking water fairly simple. Most are pump type of filters such as the Katadyn Hiker. Katadyn also makes a gravity fed filter (Katadyn Base Camp) which makes the chore very simple. Just fill the bag and hang it from a tree letting it drip into you water container while you do other things that may be a little more fun than pumping water. The the base camp filter can cost from about $70 to $100 depending on the retailer. A pump filter such as the Hiker can cost about the same. Some pumping systems are even more.
You can make your own filter system for less than $25. These are the parts you need.
Old plastic water bottle
4ft. 3/8” OD – ¼” ID vinyl tubing $2.00
Sawyer water filter $17.50
3/8 in. x 1/4 in. Brass Barb x MIP Adapter 2.80
T shirt cloth
Paint ball O-ring
The first step is to drill a hole in the cap of the water bottle to accept the brass MIP adapter fitting. I used a 1/2" Forstner bit to get I nice clean hole. I then screwed the adapter into the hole.
I cut about a 2" diameter piece of cloth from an old T-shirt and using the O-ring fit it over the brass adapter on the inside of the water bottle lid. This will keep any large debris from clogging the output.
To connect the filter to the brass adapter and for the output line from the filter I used vinyl tubing. Finally I duck taped a piece of para cord to the bottle for a way to hang it.
You could use a larger water bottle if you need to filter more water in one batch, but I think for my own personal use this one liter bottle should be sufficient. If I need more I'll filter another batch. In order for the water to flow the lid on the bottle needs to be loosened so that air can enter to replace the water flowing out, otherwise it will vacuum lock and now water will flow. You could drill a small hole in the bottom of the bottle, and plug it with a make-shift removable stopper. I also add a small paper clip to hole the output line to the pure water container. The filter, tubing and the clip go inside of the water bottle for transport.
I used this filter on a solo kayak trip in Quetico Provincial Park Ontario Canada this year. I ended up boring a small hole in the top of the water bottle to keep a vacuum from forming inside the bottle as water tried to flow out through the filter. That would stop the flow. About a 1/16 diameter hole is all that was needed. I also removed the cloth pre-filter to clean it, when it became clogged with pollen.