Finding a good lining or container to hold the water in the inside of the box as it heats and evaporates can be complicated. The combination of high heat and water containing salt or other contaminents can corrode metals faster than usual and cause plastic containers to break down or offgas, imparting an unpleasant taste to the distilled water. The best liners are glass or stainless steel, although you can also coat the inside of the box with two or three coats of black silicone caulk (look for an F.D.A.-listed type approved for use around food). Spread the caulk around the bottom and sides with a taping knife. After it dries and cures thoroughly, just pour water in—the silicone is impervious to the heat and water.
How to Make a Solar Still
We chose to paint the inside black and use two large glass baking pans to hold the water. Glass baking pans are a safe, inexpensive container for dirty or salty water, and they can easily be removed for cleaning. We used two 10 x 15″ pans, which hold up to 8 quarts of water when full. To increase the capacity of the still, just increase the size of the wooden box and add more pans.
The operation of the distiller is simple. As the temperature inside the box rises, water in the pans heats up and evaporates, rising up to the angled glass, where it slowly runs down to the collector tube and then out to a container.
The runoff tube is made from 1″ PEX tubing. Stainless steel can also be used. However, use caution with other materials—if in doubt, boil a piece of the material in tap water for 10 minutes, then taste the water after it cools to see if it added any flavor. If it did, don’t use it.
View step-by-step photos of how to make a solar still in the Image Gallery as well as this PDF of the DIY Solar Still Plans.
1. Mark and cut the plywood pieces according to the cutting list. Cut the angled end pieces with a circular saw or tablesaw set to a 9 degree angle.
2. Cut the insulation the same size as the plywood base, then screw both to the 2 x 4 supports with 2 1/2″ screws.
3. Screw the first layer of front and side pieces to the base and to each other, then add the back piece. Predrill the screws with a countersink bit.
4. Glue and screw the remaining front and side pieces on, using clamps to hold them together as you predrill and screw. Use 1 1/4″ screws to laminate the pieces together and 2″ screws to join the corners.
5. Glue and screw the hinged door pieces together, aligning the bottom and side edges, then set the door in position and screw on the hinges. Add a pull or knob at the center.
6. Paint the inside of the box with black high-temperature paint. Cover the back and the door with reflective foil glued with contact cement. Let the paint dry for several days so that all the solvents evaporate off.