|This page covers the most-often asked questions about new well installations, and includes a little information about off-grid power systems. It also has some helpful advice about system maintenance. |
What exactly is a submersible pump?
A “submersible” consists of a small-diameter motor mated to a pump. The assembly is installed submerged in the water, down inside the well casing. Most residential wells use a four-inch casing, with the submersible being three and a half inches in diameter. Commercial or high-production wells and pumps are larger diameter. Length of the submersible varies, with higher horsepower, higher-output units being longer. For example, a half-horsepower (HP), five gallons per minute (GPM) submersible is about two feet long, and a 2 HP, 10 GPM submersible is about four feet long. There are many combinations of pump and motors, and the choice of the combination is critical. Obviously the units need to be more powerful for deeper wells, or if higher water production is desired. Special models are sometimes used for off-grid power applications. It's also important to consider the velocity of the water being pushed to the surface. It must move at sufficient speed to carry solids (like sand, if present) to the surface, so that they don’t remain suspended in the water in the pipe string where they might cause problems. Other considerations are any additional distance the water must be moved once at the surface (to a house or distant tank for instance), and the distance to the power supply. Since the choice of motor horsepower, pump output, pipe size, and wire size is dependent on the application, the pump installer needs to know these details before choosing the equipment, or setting the price.
What does the control box do?
Submersibles usually require a separate above-ground, electrical control box to supply the special power needs of the submersible motor. The control box location depends on the individual installation, but it’s often installed at the well head.
Do I need a pump saver?
These are highly recommended devices which monitor the electrical voltage and current used by the submersible. If the current drops, which usually indicates that the water level has dropped down to the pump level, then the device shuts off the submersible to prevent damage. The device will also help prevent damage caused by low voltage or electrical surges, which can happen with any type of power system. Pump savers come in several varieties, and some have additional features.
What other components are required?
The submersible is installed by lowering it down the well on the end of a string of pipe. The pipe is added one length at a time as the submersible is lowered. One-inch diameter pipe is used most often on residential installations, but larger pipe is occasionally required if higher rates of water production are needed.
For smaller submersibles installed to depths of about 500 feet, schedule 80 PVC (plastic) pipe with threaded couplings can be used. This pipe has a thicker wall than similar pipe that you might be used to seeing in irrigation systems for example. The schedule 80 pipe is designed for the task. It's lighter and less costly than steel, and doesn’t corrode. A safety rope is installed alongside the PVC pipe in order to have a means of removing the submersible in the remote event that the pipe should break. A torque arrestor, which is a device to center the pump and minimize its twisting on startup, is installed above the pump.
In some cases, galvanized steel pipe is used. That's because beyond a certain depth, the combined weight of the submersible, pipe, wire, and water contained in the pipe, would be too heavy for PVC pipe. Steel pipe is also used at shallower depths for larger submersibles, where the twisting of the motor when it starts (torque) might damage PVC pipe. Galvanized steel pipe is stronger, but is also heavier, and subject to eventual corrosion. A safety rope is not required in these installations.
No matter which type of pipe is used, one-way check-valves are installed at intermediate distances along the pipe string, to prevent water from draining back down the well when the submersible is shut off. The wire, and safety rope if installed, are lowered at the same time as the pipe string, and securely fastened to the pipe along its length.
The pipe string exits the well casing through a well cap. Surface plumbing varies with each installation, but may include a hose bib (for taking water samples), and a pressure-relief valve to vent excess pressure in case of malfunction.
What is the pressure tank for?
Pressure tanks of various sizes are used to supply water pressure even when the submersible is stopped. A pressure tank is cylinder shaped, made of steel or fiberglass, and is generally about four feet tall and two feet in diameter. Inside is a rubber bladder, which takes up about half of the capacity of the tank. The remainder of the tank (usually the top portion) is air space. When the submersible is running, water is pumped into the bladder. As the bladder fills, it enlarges, causing the air in the space above to become compressed (the water itself cannot be compressed). Once the bladder is full, a pressure switch shuts off the submersible. When a faucet is opened, water flows out of the bladder, pushed by the compressed air. After a certain quantity of water is used, the bladder is near empty, and the pressure switch activates the submersible again to cause the cycle to start over.
What about storage tanks?
Storage tanks come in many types and sizes. Their purpose is to provide a larger supply of water from which to draw. In addition, they ease the burden on the submersible, since it can be controlled to fill the tank at a different time, or during a longer period, than when the water is being used. For instance, with a marginal well, where the well’s output is insufficient to meet peak demand, a storage tank can be filled steadily at a slow rate, and the water withdrawn from storage at a high rate when needed. This strategy maximizes the water production of the well. Another benefit is that stored water is available should the well be disabled for any reason. And, if necessary, water can be delivered from an outside source and stored in the tank.
Storage tanks are occasionally placed at a high elevation. The submersible pump fills the tank, and gravity alone provides water pressure for the house. For example, if the storage tank is 100 feet higher than the house, then the water pressure at the house will be about 43 pounds per square inch (PSI). Since most properties don’t have a sufficiently elevated tank location, the water pressure is instead provided by a separate pressure (jet) pump. The submersible pump fills the storage tank (controlled by a liquid level control in the tank), and the pressure pump (controlled by a pressure switch) fills the pressure tank.
Storage tanks in this area are often plastic, above-ground models. Popular sizes are 1500 and 2500 gallons. These units are long-lasting, relatively inexpensive, and easy to transport to difficult locations. They require about an eight foot diameter space, which need only be flat and rock free. Buried tanks are also available.
How does the well pump know when the tank is full?
A liquid level control turns the well pump on and off. These are usually automatic, float-type switches installed inside the storage tank. When the level of water in the tank drops below the desired setting, the float switch operates an electrical relay switch to turn on the submersible pump. Once the tank is full again, the system shuts off the pump.
I'll be using a generator during construction of my home, can I use it to power the well temporarily?
Yes, that's a common practice. The choice of generator size, type, and fuel will depend on many factors. 5 KW is the minimum size of generator to power residential well pumps installed at moderate depths. Deeper wells, or those with larger, higher-output pumps will need generators of up to 10 KW, and occasionally even bigger. Light-duty generators work well enough for temporary or occasional use. Those intending to use the generator as a permanent part of their power system should consider industrial-duty generators, which are generally designed to be quieter, more fuel efficient, and longer lasting. Electric start is a desirable option for larger generators, or those which will be started by remote control. If it's your preference to use a smaller generator, then we can supply a pump designed to accommodate that.
Are these water systems difficult to operate and maintain?
Most residential water systems require very little maintenance, but there are a few things worth keeping an eye on.
Water quality - Well water should be checked occasionally for bacterial contaminants.
Storage tanks - Take a look inside occasionally to check for sediment building up on the bottom. Excess sediment can end up in your household plumbing, or harbor bacteria in the tank.
Electrical controls - Repair any damage to shelters which might allow water or rodents into controls. A common problem is ants fouling the contacts in pressure switches.
Pressure tanks - These are maintenance free, but you can prolong their life by keeping them out of the hot sun if possible. The only problem is with age they can develop small holes in the bladder that increases over time. This will cause your pump to start and stop often and shortens the life of your pump.
Well head, surface plumbing - Promptly repair any physical damage caused by animals chewing on components or insulation, etc. Fence off the area if necessary. Keep above-ground plastic plumbing shielded from the sun. Check your entire installation before winter to see that insulation is adequate. Marginal wells should have draw-down tests performed occasionally to verify that control timers, etc., are set up properly and functioning. Valves should be operated occasionally to prevent them from becoming stuck in position, especially if the mineral content of the water is high.
Off- grid power systems - Keep insects out of inverters and controls. Keep vents clear of dust and debris. Check batteries often for proper water-level and verify that connections are clean and tight. Prevent batteries from being exposed to freezing temperatures, especially when charge levels are low. If powered by an engine-driven generator, don’t let the generator run out of fuel while the well pump is operating. Check occasionally for proper voltage output.
General advice - Know your system. It’s best to be familiar with the sounds and cycle times of the components. This way you’ll recognize symptoms early, such as too-rapid cycling of pumps. Be sure the system is equipped with a pump saver device if there’s any possibility of low water or faulty electrical supply.
What types of problems arise as these systems age?
Properly installed and maintained systems generally perform well for many years. But here are the most common problems, and their causes.
Early submersible failure - Pumps sometimes fail early if they’ve been sized incorrectly, or have been pumping excessive contaminants. Motors can fail early if they’ve been subjected to poor power supply, such as inadequate wiring or fusing, or being repeatedly allowed to run at low voltage as the generator runs out of fuel. Running the pump dry will also cause premature failure. This can happen if the pump electrical controls are inadequate for use on a marginal well.
Pressure tank failure - Pressure tanks often last a very long time, but occasionally they can be short-lived. The average lifespan is probably about five years. Fewer operating cycles equals longer life, so the tank should be sized to minimize cycling. When pressure tanks fail, the submersible or pressure pump will be cycling much more rapidly than normal, which can in turn cause the pumps to fail as well.
Freezing - Above ground plumbing is subject to occasional freezing, even in our warm climate. Most problems with frozen pipes cure themselves once it warms up. But pipes and valves can split when frozen, resulting in floods when the components thaw out, occasionally causing pumps to run endlessly and fail as a result.
What can I do to reduce service costs?
You can help keep your costs down by considering serviceability when you insulate, enclose, or fence off your system. Anything that impedes access to the components may increase your costs. Enclosures can usually be made removable. Give us a call if you need advice about how to do that. Should it be necessary to have your submersible pulled up for repair, keep in mind that the service truck will need to operate quite close to the well head. The area above the well head should be kept clear of obstructions.