Pumps are measured in GPM (gallons per minute). A normal three to four-bedroom house needs 8–12 GPM. When calculating your home's water requirements, add one GPM for each water fixture. Installing a well pump can increase the yield of your well by at least 10%.

The type of pump you need depends on two factors: how much pressure will you need to lift the water out of the well and **how much flow** will you need from your well. If you plan to use chemical additives or surfactants to help your plants grow better, these products may require **more pressure** than what a hand-powered pump can provide.

You also need to consider **how much power** your pump is going to consume if it is going to be run continuously. Most standard household electric motors are designed to run off of 120 volts alternating current (AC) from the outlet but can handle **15 or 20 amps**. Some higher quality models can run off of solar power or battery backup systems and still deliver good performance. It all depends on how often you want to use it and how long you want it to last without replacing the motor.

Well pumps come in many sizes from small hand-pumps that can lift up to 1 gallon of water per minute to large electric submersible pumps that can lift 50 gallons or more every hour.

For every 10,000 BTU of heat load, the circulator must deliver a 1 gallon per minute flow. Assuming that the system requires 100,000 BTU/hr, a circulator pump should have a minimum flow rate of 10 gallons per minute at a certain pressure drop. For example, if the pump has a 4-inch diameter mechanical shaft, it should be able to deliver 40 pounds per square inch (psi) or more at 10 gallons per minute, which is enough to circulate hot water through an 8-inch pipe.

The sizing process begins with determining the heat load. The easiest way to do this is by using **a thermal couple** and measuring the temperature rise across two different sized copper wires that are connected directly to each side of the couple. Be sure to use thermally rated connectors on the wires leading into the couple tool.

Next, determine the maximum working pressure of the pump. This can be found by multiplying the maximum operating speed of the pump by its delivery head. For example, if the pump runs at 3,600 revolutions per hour (rpm), with a 2-foot delivery head, then its maximum working pressure is 9 inches of mercury (inHg).

The final step is to calculate the required horsepower. This is done by dividing the maximum working pressure by the frequency of operation.

20 GPM is roughly equivalent to If we want to run a 15,000-gallon pool 24 hours a day, we need **around 20 GPM** of flow. Most pools operate on an 8-hour on/16-hour off (stagnant) schedule. This means that for every hour the pool is on, it gets pumped for **about half that time** (4 hours instead of eight). For example, if it took 1 hour to fill the pool to capacity and 0.5 GPM was required, then you would need 10 GPM of flow.

The easiest way to determine how much flow your pump needs is with this simple formula: Flow needed in gallons per minute = Pool size in gallons times 0.6. So if your pool is 15,000 gallons, you will need 20 GPM of flow.

Pumps are rated by their horsepower (HP), which is measured in watts. One horsepower is equal to 746 watts. So, the more horsepower your pump has, the faster it will move the water. Pumps come in **different sizes**, from small 25 HP models that can be used in small pools to large 500 HP units that can lift hundreds of pounds over the side of a boat.

The number that most people get confused with is gpm. This stands for gallons per minute and is the amount of flow that your pump will push through **its outlet pipe**.

Example: Specific Speed for a Pump in Various Units

- US gpm, ft. Ns(US gpm, ft) = (1760 rev/min) (1500 gal/min)1/2 / (100 ft)3/4
- British gpm, ft. Ns(British gpm, ft) = (1760 rev/min) (1249 gal/min)1/2 / (100 ft)3/4
- M3/h, m. Ns(m3/h, m) = (1760 rev/min) (340 m3/h)1/2 / (30.5 m)3/4
- Liter/min, m.

According to the Water Well Board, the minimum water supply capacity for usage inside a dwelling should be at least 600 gallons in two hours, or approximately 5 gallons per minute for two hours. Install one or more of these wells to meet **this requirement**.

The amount of time it takes to pump 600 gallons is dependent on the size of the pump and the depth of the well. A household using less than 10 gallons per day (gpd) could get by with a single well that produces **20 feet** per minute (fps), but if you use more than 10 gpd you'll need another well to meet the board's requirement.

In addition to storing drinking water, wells also provide energy for pumping it. The amount of energy needed depends on how much water is being pumped. For example, it would take 1 hp motor to drive a 30-foot-per-minute pump over **its full range** of movement, but only 0.5 hp for a 6-foot-per-minute pump. Lower speeds require less power. Deep wells require more power because they tend to have **slower flow rates**. A household using 15 gpd would need a well with a flow rate of about 40 fps to meet its energy needs.

Wells can be either open air or closed systems.