Homemade Emergency Water Filter

Prior to moving in I am spending my weekends gathering camping equipment and sundries for the new place.  Being somewhat of a remote location, it is essential to have the basics on hand.  The current economic turmoil has heightened my sense of preparedness.  Becoming prepared is a way to cope with the uncertainty of a collapsing dollar.  A vacation home can serve as a supply cache and base camp.  In the worst-case scenario, our family may take refuge there indefinitely.

High on most survival lists is a safe and adequate source of water.  Many emergency situations can render a public water supply inaccessible.  Electric well pumps become inoperable in the most temporary of blackouts. Fortunately, the river near our property offers an abundant supply if its water can be made potable.  Sunshine and boiling are methods for making water safe, but they take time and, in the latter case, energy.

I saw recently a post on SurvivalBlog.com about making an emergency filter for pond water.  Here I document my adaptation of their design and explain how it differs.  This project costs only about $15 using two 5-gallon buckets, a short section of 3" dia. PVC drainpipe, 2-3 lb. active charcoal, and about 400 cotton balls.  I'm going to assume you can find sand and rocks.  An optional lid for one of the buckets can be used to store the device neatly until it gets used. A large paper filter, like one used in a coffee machine, is not required but further increases the effectiveness of this device.

Active charcoal is sometimes called activated, or active, carbon.  It is said to be active because its tiny particles have an amazingly large surface area that cause it to trap impurities.  One site says that a mere 10 grams has the surface area of a football field.  Active charcoal can be purchased in the aquarium section of big box stores, or on-line from aquarium suppliers.

The only tools required to construct this filter are a jigsaw or hacksaw, a 1/8" drill, tape measure, and marker.  Cut a piece of scrap PVC drainpipe to a length of about five inches.  Set the pipe in one of the buckets vertically so that one opening of the pipe rests against the bucket and the other is up.  Set the second bucket inside the first on top of the pipe.  Draw a line around the second bucket using the top edge of the first bucket as a guide.  In other words, you need to cut down the inner bucket to fit completely inside the outer one.

If you have a lid, you will need to cut the inner bucket a half-inch shorter so the lid does not conflict.  Cut down the inner bucket and test the fit.  Discard the top section of the inner bucket.

Use the drill to make holes in the pipe and both buckets.  In the outer (taller) bucket, drill about 20 drain holes in the bottom, near the center.  In the pipe, drill about 20 holes along the edge of either opening.  (The opening in the pipe with these holes goes down when the filter is assembled.)

Finally, drill holes in the bottom of the inner (shorter) bucket, but not in the center.  Instead, place the pipe against the center of the shorter bucket as a guide, and drill the holes halfway between the pipe and the outside edge of the bucket.  The holes should make a big circular pattern about one-third of the radius of the bucket.

To assemble the filter, lay the pipe in the center of the taller bucket with the hole side down.  Stuff cotton around the pipe to hold it in place.  The cotton should come up roughly half the height of the pipe.  Pour active charcoal on top of the cotton, filling it no higher than the top of the drain pipe.  Insert the shorter bucket into the taller bucket so that it rests on top of the pipe and charcoal.  Fill the inner bucket one third with sand, followed by one third with pebbles, and finally topped with gravel.  If you have a coffee filter, leave a small depression in the layer of gravel.  Place the coffee filter on top to form a shallow dish shape in the center.

To operate, position the filter on top of a catch-basin or large pot.  Pour pond water into the top, about a gallon at a time until you get used to the flow rate.  If I get really bored some weekend I may build a stand for the filter so the pot fits beneath.

When not in use, dry out the parts; put duct tape over the drain holes to keep dirt and bugs out; store a fresh supply of cotton and charcoal inside; and cover with the lid.

The original design called for multiple layers of rocks, charcoal, and cotton, each about one inch thick, whereas my design has only one layer of each.  The problem I have with the repeating layers design is that it becomes difficult to visually check the charcoal, and to replace the charcoal and cotton.  It would be hard to separate the charcoal and cotton from the rocks if they were in multiple layers.  In my design you just remove the inner bucket.  If there is a benefit to having repeating layers I would argue that the same effect can be had by running the water through my design several times.  Of course, if you have any concerns about the quality of water that comes out, boil the water before consuming.

Have fun building the filter and using it.  Hopefully we will never be forced to use it.