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Simple Solar Water Distillers

What could be easier than purifying water using the sun? Solar water distillation is an amazingly easy and natural process, and it is fairly inexpensive to build a solar distiller. Stills are FREE to use (using only the sun’s energy), require no electricity to run, plus there are no expensive filters to replace. The distillation process is based on how rain is made—through evaporation and condensation.

solar water distiller

How rain is made–evaporation and condensation.

How does a solar water distiller work?

A solar still is an insulated oblong box with angled glass on the top. The sun shines through the glass and heats the water in the basin, which evaporates and then condenses on the glass. The condensate then rolls down the glass and into a trough and out a tube into your collection jar.

How much water does a solar still make?

Solar water distillers that have about 10 square feet of glass (usually in sizes of 3’x3’ or 2’x4’) will typically produce about 5 liters of water per day in summer, and half of that in winter, on a sunny day. If you have a family you will want to have two distillers instead of one, in order to produce enough for your cooking and drinking needs.

How good is solar distilled water?

Distilled water is not just pure, it is ultra-pure, which means it is completely devoid of anything except pure H2O. In fact, it can be fairly tasteless so some people add minerals back in, or you can shake it up and oxygenate it briefly so it tastes sweeter.

However, solar distilled water naturally tastes better and is around a neutral 7 pH compared to ‘forced-distilled’ water (through boiling), which tastes metallic and is acidic. The reason for the difference is because solar distillation uses the natural slower process of evaporation and condensation rather than forcing it through heating elements (which cost money to run) to evaporate the water, and mechanical fans to cool it so it will condense.

solar still

Solar water distiller

What contaminants are removed?

All contaminants are removed since distillation is a physical process, including:

Particulates: salt, sand, sediment, rust, iron flakes (from old pipes), debris

Pathogens: bacteria (like fecal coliform that causes cholera), and microorganisms (such as E-coli, giardia, or chryptosporidium).

Other contaminants: chlorine, fluoride, arsenic, lead, mercury, salts

The only thing that might get through the distillation process is volatiles like gasoline or kerosene, although just make sure you do not put water into the still with volatiles in it. These will distill out before the water does because they have a low boiling point. However, you can put a small standard carbon filter (available at most hardware stores for a few dollars) at the exit tube on the still and it will render the water safe to drink from any possible volatiles that may have accidentally made their way into the still.

How easy is it to build a solar water distiller?

It costs a few hundred dollars to build a solar water distiller. I have made them out of concrete but it is a lot of work. The best designs are typically wicking or multi-trough stills but they tend to be complicated to make and are higher maintenance. The easiest still to build and to use is by far the single basin still.

solar distiller workshop

Solar still workshop

The single basin style distiller is a box that has insulated walls and bottom, with a piece of glass attached to the top, sloped at about 10 degrees. A water catchment trough runs lengthwise at the bottom edge of the glass and allows the condensate to run out into a silicone tube into your collection vessel, which is usually a glass jar. These stills are excellent because if they freeze in the winter it does not hurt them, and when the sun rises it just heats up and starts working again automatically!

It is extremely important not to use unsafe materials that could gas off or put toxins into your distiller or distillate as it could poison the water or make it taste bad. Plastics should be avoided at all costs. Silicone is often used for the inside of the still, but only a food-grade silicone.

There are also kits available online through SolAqua for those who wish to get the hard-to-find items. See my page regarding solar water distiller kits here.

I also have a free e-book that covers more details here on how to make a solar water distiller:

Have fun with the sun!

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