Water Systems For Off-Grid Living
By Dan Fink
A steady supply of drinkable water is the single most important factor in deciding where to settle down and live. It has shaped humankind’s migrations since prehistory, and people suffer when water suddenly becomes scarce. Most of us in the U.S. are used to tasty, unlimited water right out of the tap — until the next disaster strikes and the city water supply is disrupted, or the electricity goes out and the well pump no longer works. This is when a water system for off-grid living can be a life saver.
Living off the grid can actually provide a tremendous amount of water supply security, but it is also often the single biggest hassle. You are both the water company and the power company, and when things go wrong and you can’t fix the problems yourself, the response time when you call for help will be extended and the bill hefty.
System Design Philosophy
The single most critical factor in planning an off-grid water system is to store as much water as you possibly can, right in, under or next to the house. This gives you a tremendous amount of flexibility, as you can utilize multiple methods to fill that cistern, and if your method requires electricity you can choose to run that pump only when you have extra incoming energy to burn. Electrical loads you have no control over are the bane of off-grid living (see Country-side, January/February 2015, for an example of an uncontrollable load: refrigeration) Think of your cistern as a “battery” of sorts, which buys you time until you need to pump again. Even better, compared to electrical batteries, cisterns are inexpensive and last nearly forever. I recommend a minimum of 400 gallons of water storage for a typical off-grid home, with 1,000 gallons or more even better (Photo 1).
Another aspect of this flexibility is that a cistern lets you move water slowly over a longer period of time, so the pumping equipment requirements can be far less expensive. Consider a typical on-grid water system that pumps from a well: Only a few gallons of water are stored in a small pressure tank, and when you take a shower and the pressure drops, the big well pump turns on to both lift the water out of the ground and to pressurize your faucets and shower head. With a cistern, all that turns on is a small pressure pump in the house that has low power needs.
Your choice of water source for an off-grid home will depend entirely on your geographic location and the resources in your area. Each source comes with its own development hassles and expenses, and also with its own equipment requirements. Also, be sure to keep in mind the end use of the water—humans need very pure water for daily life, while livestock and gardens are not so particular. Any type of purification equipment will add expense and complexity to your water system design, and some contamination simply cannot be recti-fied economically.
Local Water Fill Stations
These are the worst possible solution to an off-grid water supply, but most western municipalities and counties operate “ranch water fill stations” that operate from a pre-paid card. The water itself is usually pure and inexpensive, but your time and costs in hauling it are tremendous and unsustainable. Keep in mind that when the back of your pickup truck contains a big water tank, you don’t have much room left for groceries, tools and such. Wear and tear and extra fuel consumption on your vehicle from the tremendous weight of water will also be brutal.
However, if things go wrong with your homestead water system, water fill stations can literally be a lifesaver. You might be grouchy after such an emergency run to town, but you should instead feel happy and smug you have a cistern—those poor townies who don’t are buying up washtubs for sponge baths, buckets for flushing the toilet and water jugs from the camping store for cooking and drinking. All you have to do is back up your truck to your outdoor fill inlet and connect a hose, and your home will be functioning as normal. Incidentally, don’t forget to detach the hose after you’ve filled your cis-tern, and be sure to plug the water fill line with a cap so mice can’t get in. I’ve been there, done that here on both of those.
Wells are by far the most common water source off the grid, as most locations are not lucky enough to have a spring that can be developed (see sidebar) or surface water that is clean enough to economically purify for drinking. Wells—and well pumps and the off-grid electrical equipment needed to run them—are all expensive, but most people have no choice.
When you hire a company to drill your well, they’ll first walk you through the permitting process, if required by your local authorities. Once you’ve cleared that red tape and the crew shows up with their rig, your waiting period begins as you stand back and watch the show. Anxious? You should be, as they charge by the foot with no guarantee that they’ll hit water. There also may be a certain minimum depth mandated by your local authorities. Some people swear by having the well location “witched” by a dowser, but scientific studies have shown no increase in success rate. My belief is that through years of hit-and-miss experience, successful dowsers have simply developed a very good eye for terrain features in their local area that can indicate underground water.
It is possible to dig or drill your own shallow well, depending on your local water table and soil type. But keep in mind that if permits are required, you may not be able to reach the minimum depth, and the home drilling tools you can buy or rent can’t penetrate rock. Also, these systems usually bore only a two-inch diameter hole, which leaves you very limited choices in well pumps and very few feet in lift capacity, com-pared to the big boys who can drill through anything and leave you a 4 inch diameter hole, sized for any standard well pump.
After the drilling crews hit an adequate water supply, they’ll likely take depth and flow measurements, send water samples to be tested, and try to sell you a pump they will later set, wire and plumb. This is a critical juncture for you off the grid, as many companies don’t know anything about the special considerations that are crucial for off-grid electrical systems. They’ll likely want to set a standard 240 volt AC pump, but that can be a real problem. The DC to AC inverter required (Countryside, July/August 2014) will be far larger and more expensive, along with a larger battery bank. If it ends up that you can’t afford all this extra equipment, you’ll be forced to run a gasoline generator every time you need to fill the cistern, and the generator will likely need to be a big one, at least 6,000 watts—and at high altitude or with a very deep well, even larger.
Instead, as soon as you get the well data from the driller, go straight to a local or online renewable energy dealer. They’ll be able to recommend a well pump suitable for your off-grid electrical system (Photo 2) and while it will be more expensive than what the well driller wanted to sell you you’ll save on electrical equipment, whether for a new install or an up-grade. The recommended pump will have a “soft start” feature that drastically reduces the extra surge of power pumps require to start spinning, or it might be a 120 volt model so you don’t have to invest in a 120/240 volt inverter or 240 volt autotransformer. If you are reading this too late, a regular 240 volt pump has already been set, and your inverter won’t start it, don’t despair quite yet. There are new pump controllers available that can simulate soft start features and might enable that old pump to work. These controllers are expensive—around $1,000—but that’s much cheaper than buying and installing a new pump or an inverter upgrade.
If you have a spring on your property, consider yourself both extremely lucky and extremely wise for purchasing that particular piece of land. Springs are simply a terrain feature where the underground water table breaks the surface of the ground. You’ll see a greener area with thicker vegetation, possibly some standing water, and maybe even a little running water below.
To develop a spring, you’ll need to dig it out, set in a containment barrier, cover the bottom with gravel, and then lay both overflow and water supply lines. The standard procedure around here is to locate the head of the spring—the area just uphill from where standing water makes its appearance—and dig down about six feet there with a backhoe. Then, you can use the backhoe to set pre-cast concrete well rings, the bottom one perforated, the top one solid, and a pre-cast concrete lid with an access hatch and handle. The water supply line is run from the bottom of the hole through one of the perforations, and the overflow line from closer to the top. The overflow maintains water flow all winter long without freezing, and lets you set the maximum fill level.
This is all a significant investment, especially if you are not sure if the spring will have adequate flow all year to meet your needs. But you can do a test development at a much lower cost. Dig the hole by hand, and set a food-grade plastic barrel that you’ve cut the bottom out of and pierced a few holes in the sides of, near the bottom. The gravel, sup-ply and overflow lines are run in the same way as in a more major development. The final steps are to insulate the spring box and all of the lines to prevent freezing, and to fence around everything to keep out livestock and wildlife—you don’t want to find a pile of poop or a dead animal near your drinking water supply! Finally, after a few days when the sediment from digging has washed away and the water is running clear, take a couple samples down for mineral and contaminant testing by a water-quality lab. Some counties even offer this service at a reduced cost. You’ll want to take some steps to remove sediment and purify spring water before drinking it; a few of those are discussed later in this article.
The pump required to fill your cistern with spring water will usually be far less expensive and use far less energy than a well pump, unless your spring is located a long ways downhill from your house. Keep in mind that pumps can “push” water up many hundreds of feet, but are limited by atmospheric pressure as to how far they can “pull” up the water. While the theoretical limit is higher and depends on your altitude, the practical limit is only about 20 feet of pull.
My spring water system uses a standard RV pressure/utility pump (Photo 3) that cost under $100, and lifts the water 40 feet over a distance of 450 feet. The pump is located underground in a “manhole” below the spring. Submersible pumps can also be used, but are generally more expensive. In my system, the cost of the backhoe service to excavate the spring, manhole and trench 450 feet of water line four feet deep was far more expensive than everything else combined.
While usually fine for livestock and gardening, surface water is a dicey proposition for human consumption because conditions can change at any time, without warning. Yes, you can purify water, but an upstream spill of agricultural or industrial chemicals, petroleum products, or even a sudden influx of sediment can render your purification system useless and your drink-ing water dangerous without you knowing anything is wrong. A spring technically is “surface water,” but “upstream” is far underground with little chance of contamination. Unless your local surface water supply is a crystal clear mountain rivulet with nothing upstream but wilderness, leave surface water for the cows and garden and get your drinking water elsewhere. Even then, purify it meticulously due to sloppy hygiene habits of wildlife, who can carry giardia and other parasites.
Depending on the results of your water test, you may need to install filtration, purification and condition-ing equipment. Sediment is the first issue to address, as it gives your water an off color, and can quickly ruin water heaters and pumps along with clogging water lines and filters, with larger particles settling on the bot-tom of your cistern in an ugly layer. Many purification systems have strict requirements on maximum particle size that can be passed to them, and failure to follow these requirements will result in unsafe water, rapid system failure, or both. A good sediment filtration system will be based on the size of particles discovered during your water tests, and usually consists of a series of filters that first remove larger particles, working down to progressively smaller sizes. Proper design is essential, as sending big particles to a super-fine filter will quickly clog it. Some filters can be back-flushed to partially clear them, but filter life will still be shortened.
Water filtration makes your water pretty and protects your equipment, while water purification makes it safe to drink. The two primary methods used are reverse osmosis (RO) and ultraviolet (UV) light. RO filters are the most common, and use your system’s water pressure to force impure water into a semi-permeable membrane. Impurities, bacteria, viruses, dissolved minerals and such aren’t passed though and go straight down the drain. Sediment will quickly clog the expensive membrane, so a series of replaceable pre-filters are always included. Be sure to follow the manufacturers recommendations on maximum particle size you send to their first filter; depending on your water source you may need to add additional filters in line before theirs. Because reverse osmosis also removes dissolved minerals, it is effective for “hard water” mineral problems. A whole-house RO system can be very expensive, but more affordable RO systems (Photo 4) are available that mount under your sink and supply purified water to a separate faucet that is included with the system. This can be an economical choice as if your water is reasonably clean to begin with, there’s no need to purify bath-ing, sanitation or gardening water.
UV purification is a newer choice in the home market, and is also very effective. Water is passed through a flow restrictor into a tube containing an ultraviolet lamp, which kills bacteria, viruses and protozoa (Photo 5). It is critical to follow the manufacturer’s instructions on pre-filtering down to a maximum sediment size or your water will not be purified, as nasties can ride along on bigger particles and survive the UV light. UV systems also do not affect water hardness, so you still may need an additional “water softener” conditioning system depending on your water quality. The UV lamp uses electricity, but only at a modest rate, ranging from 30 to 150 watts for a typical home, depending on the system flow rate. Most are designed so that the lamp to stays on at all times, and this constant power draw might be too much for a small, off-grid electrical system. In that case, it’s possible to add equipment to make the lamp come on only when water is being used, and also adding an automatic cut-off valve so there’s no possible chance of un-purified water getting past the UV unit. Most UV systems are designed to supply the entire house instead of individual faucets.
Most off-grid filtration and purification systems are configured with the coarse sediment filters between the water supply and cistern, using the well or spring pump to water through. This prevents sediment buildup at the bottom of the cistern, while keeping reasonably clean water in there. It’s recommended that you disinfect the cistern yearly; this is usually done with a small amount of bleach. Contact your local county extension for the recommended dos-ages and times.
Your home water pressure pump will first pull water from the cistern, and send it under pressure to fill a smaller “pressure tank” (Photo 6) with a bladder inside that maintains steady water pressure for your faucets. These usually range from five to 40 gallons, and the bigger the better—pressure tanks even out surges in water use (like when someone flushes a toilet when you’re in the shower) and extend pump life, as the pressure pump doesn’t have to turn on every time a faucet is opened.
Look carefully at how many Watts of power your pressure pump needs, both to start up and to run. Some models and brands use far less than others, which is important off the grid, and there’s no need to oversize the pump. Mine is an inexpensive RV pressure pump, in fact the same model I used for pumping from my spring to the cistern, and it readily handles any two fixtures being used at one time. You might even consider getting your pressure through your local or online renewable energy dealer, who can recommend a model sized for your needs, but with mini-mum power draw.
I am often asked about using gravity feed pressure—a water tank up on a hill—but I only recommend this for agricultural applications. In a home system, with gravity feed the pres-sure at your taps will vary depending on how full the tank is. On-demand water heaters need steady pressure to maintain even water temperature, and won’t turn on reliably if pressure drops too low. Also, filters and purification systems require extra pressure to operate, which is best provided by a pressure pump.
PV-Direct Water Pumping
We already discussed the basic design philosophy for off-grid water systems: pump slowly to save on expensive equipment, do it only when extra power is available, and pump into the largest cistern you can fit at your home. As it turns out, some water pumps are designed for DC electric supply (Photo 7) and can run directly from solar electric (PV) panels, with no expensive batteries or inverter required. These “set and forget” systems are a joy to work with, and pump away on their own whenever the sun is out. By adding float switches and a pump controller, the system can be designed to shut off when the cistern is full or the water source is getting low.
PV-direct pump controllers (Photo 8) also contain circuitry called a linear current booster (LCB), which senses available power and allows the pump to start up and push water earlier and later in the day, and even on overcast days, though at a slower rate. But with a big cistern of water as your “battery,” the rate is not so important. PV-direct pumping has disadvantages, though. The main one is that the solar panels are dedicated to the pump—they can’t also be used to charge the battery bank in your off-grid home. Also, the higher, faster and farther you have to push the water, the more solar panels are needed. Another disadvantage can come if your cistern is small, usage high, and you get hit by an extended period of bad weather. There you are with an empty cistern, full batteries in your house thanks to the gasoline backup generator, and no way to run the pump. For those reasons, most PV-direct systems are seen in agricultural applications, where they are perfect for remote watering of crops and livestock.
While off-grid water systems can provide a great deal of water security for your family and your homestead, they can be complicated to design and install. It’s no fun spending thousands of dollars on drilling, in-stalling pumps and equipment, and burying water lines only to find out your inverter isn’t powerful enough to start the pump, or your pump isn’t powerful enough to lift water all the way up to your cistern. Even experienced system designers and installers occasionally run into these issues, and I always (secretly) have my fingers and toes crossed when a new pumping system is fired up for the first time.
Fortunately, help is available. Most local and online renewable energy dealers will take the informa-tion you and well driller provide, and design an efficient workable system for you that’s easy to live with. If there are any hitches during or after installation, they’ll also be able to help you solve the problems at the lowest possible cost.
Water Terms And Facts
• A gallon of water weighs about 8.33 pounds.
• It takes 833 foot-pounds (or 0.0003 kilowatt-hours) of energy to lift one gallon of water 100 feet.
• Water is most dense at about 39°F, and becomes less dense as it gets colder. It is one of very few substances where the solid form floats on the liquid form. If it were not for this unusual property, lakes would freeze from the bottom up, killing all aquatic life. The ice also insulates the liquid water underneath from cold air, so the lake freezes more slowly.
• A column of water one foot high exerts a force of 0.433 pounds per square inch underneath it.
• One pound per square inch of pressure will lift a column of water 2.31 feet.
• Head = The vertical distance (and therefore pressure) needed to lift water from your well to your cistern.
• Total Dynamic Head = Head, with the extra pressure needed to overcome friction from all vertical and horizontal pipes, valves, and filters added in.