From GENE LOGSDON
Excerpt from Practical Skills 1985
Where well water is not conveniently available in the country or is so hard that it rusts the plumbing out in only a few years, a cistern is not the old-fashioned impracticality most of us moderns believe. A neighbor, Gerald Frey, who is in the construction business, just finished building himself a new house. He equipped it with a large cistern — not difficult for him to do since he is one of the few builders I know who still builds cisterns commercially. “We don’t get too many calls anymore, except from members of our own family. We’ve all been brought up on cisterns and much prefer the taste of rainwater.
Although a good cistern costs as much as a well, Frey points out that from then on the savings are all on the side of the cistern: no water softener needed, no monthly charging with salt. The cistern pump is far cheaper to run than a well pump. Rainwater requires less soap to get a clean wash and glistening hair. Clothes are not stained yellowish as from hard water. And corrosion from rainwater is far less than from hard.
A cistern can be built of any material that can be sealed against leaks, and in any shape. Frey builds round cisterns out of brick. His is large — 14 feet deep and 19 feet in diameter. The wall needs to be only one brick thick because the earth has the same effect on a round form as a roof has on an arch — the harder the earth pushes in, the tighter the wall. The bricks are then plastered on the inside and then to insure against leaking, a coat or two of masonry paint is applied over the plaster. The first row of bricks is laid right on the hard clay ground; 14 feet down no footer is needed on the hard clay because there will be no frost heaving that far below the surface. The concrete floor of the cistern is poured (4 inches deep) after the walls are up. That anchors the bottom of the wall solid. “I don’t like to lay the bricks right on top of the concrete,” explains Frey. I’m afraid the pressure might crack that juncture between wall and floor and spring a leak.”
Frey employs two different filtering systems. He makes (and sells since they are not commonly available anymore) a tin box that fits on the side of the house. The downspouts from the roof feed into the box. Inside there is a screen of hardware cloth, positioned on a slant, with an opening to the outside of the box at the bottom of the slant. Water falls right on through the slanted screen, but leaves and other large pieces of debris roll down the screen, out the exit and onto the ground. A metal plate at the exit slot swings outward so the dirt can fall out, but not in, and so birds cannot get inside. A second horizontal screen at the bottom of the box catches smaller debris. Below the filter box, the water enters an upside down Y junction, where by shifting a deflector pipe, the water can be diverted out on the ground (or into a barrel) or allowed to go on into the underground tile that takes the water to the underground concrete filter box on its way to the cistern.
After a period of dry weather, when some dirt is bound to gather on a roof, the first few minutes of rainwater is customarily deflected away from the cistern until the roof is washed off. Some cistern users save no water that falls in May, June, July, or August — “save water only in the months that have an R in them,” the old saying goes. The reasoning behind this practice is that warm summer water is likely to become stagnant in the cistern. Frey agrees that snowmelt water is the best for cistern water, but his family saves summer water, too, because they use water up relatively fast. With a good filtering system, they have not experienced problems with stagnant water.
The underground filter box is divided into two compartments, the first taking up about one-third of the box. The downspout feeds into this compartment, which is separated from the rest by a metal screen. The screen sits up on a raised base off the floor so water flowing through it must rise to a certain level first. The partition below the screen acts like a trap. Dirt in the water waiting to flow through the screen settles out there.
On the other side of the screen is a section of charcoal, taking up another one-third of the box, and behind that a section of gravel. Water is purified by the charcoal and further filtered by the gravel. The outflow pipe is also screened, or the water might wash gravel on into the cistern. The pipe is up off the floor of the filter box about 8 inches. This allows water to gather in the gravel below the outlet and again trap out any dirt that might remain in it. The filter box must be cleaned and recharged about every five years.
Filtering water into a cistern is not a standard procedure. There are many methods different from Frey’s. In one kind, the filter box is a very elaborate affair, made up of three compartments about 10 inches square and 5 feet deep. Water enters the first compartment and rises up through the second compartment, through layers of gravel, charcoal, and sand, then into a third compartment where it goes back down again through three more layers of sand, charcoal, and gravel, and then out to the cistern. The drawback in cold climates is that the outlet is already 5 feet below ground level, and so the cistern must be even deeper.
A rare type of filter divides the cistern itself with a brick wall. The brick, being porous, filters the water. Another cistern design incorporates a filter box full of sharp sand, and two well points stuck into the sand draw off the water and relay it to a tank in the basement.
A final caution: it is best not to build a cistern or filter box close to a tree. The roots might wreck it.
More Practical Skills from Gene Logsdon can be found here…