The water pump is an often-overlooked piece of equipment that is many times essential for rainwater harvesting practice and systems. Water pumps are regularly needed as many water-using activities and desired ways of using the water require a certain amount of water pressure to properly work. Examples such as lawn and garden sprinklers, irrigation systems, spray nozzles, and soaker hoses, will need a water pump in most cases to sufficiently pressurize the rainwater for use. All systems that will use rainwater to serve indoor applications will absolutely require a water pump to provide the water pressure needed by the fixtures or appliances.
In this article, we will outline several of the top recommended water pump types for rainwater harvesting as well as their engineering, specifications, and other important points.
Top Recommended Water Pumps for Rainwater Harvesting
In brief, there are four types of water pumps commonly recommended for use in rainwater harvesting systems. Top recommended rainwater pumps are the electric diaphragm water pump, the submersible water pump, the booster pump, and the solar powered water pump. Each of these pump types are covered in more detail in the sections below.
All recommended rainwater pumps are engineered to be low noise, quiet in operation, easy to use, easy to install, convenient, consistent, and reliable. Pumps are compact, made of high-quality, long lasting materials. Higher cost models often require a pump controller or feature an integrated controller to provide consistent water pressures and run-dry protection.
Electric Diaphragm Water Pumps
Electric diaphragm water pumps are perhaps the simplest in design, installation and use, are low maintenance, and often the lowest cost option among the different water pump types.
The description of these pumps as “electric” is not to say the other pump types are not also electric, but rather to distinguish from other diaphragm style water pumps that are gasoline, PTO, or hydraulically powered.
Electric Power Options
Electric power diaphragm pumps are often available in different power voltage options. There are 12 volt types that can be powered by car-type batteries or PV solar systems, 115 / 120 volt pumps with standard power cords for use with typical wall outlets, and 230 volt pump types.
Engineering and Design
The “diaphragm” part of this pump option refers to the mechanism and how the pump operates to move water through the pump and plumbing. Like the diaphragm in the human body that moves air in and out of our lungs, a synthetic diaphragm in the water pump moves water in one side of the pump and out of the other, creating water pressure and water flow from inlet to outlet through the plumbing system. In the case of a rainwater harvesting setup, the rainwater would be pumped from the storage container to the lawn sprinklers for watering the grass and landscape.
Electric diaphragm pumps are simple in make and feature few moving parts. This contributes to a lower purchase cost as well as lowers concerns of maintenance and wear-and-tear.
Specifications and Cost
Many diaphragm pumps are available sized to fit common garden hoses or irrigation type pipes and plumbing. Common sizes include 3/8 inch and 1/2 inch. Water pressure outputs for electric diaphragm pumps can range from less than 40 PSI to 60 PSI. Flow rates can range between 1 GPM to 6 GPM (gallons per minute). Most are designed to be turned on for use and then turned off when no longer needed. Prices for diaphragm pumps can range from $90+ to $300+.
Submersible Water Pumps
Submersible water pumps are unique as they are made to be installed on the inside of a rainwater cistern. This pump type is intended for long-term placement and use while being completely submerged within water. They are designed to be safe and reliable. The internal installation eliminates any concern with outdoor weather exposure as well as the need to match up width and diameter sizing of the plumbing system to fit hoses or pipes that will be used with the pump. Submersible pumps are often designed to attach to the outlet valve within the rainwater container, making this the only location where size matching is needed.
Electric Power Options
Submersible rainwater pumps are most often 115 / 120 volt electric powered and feature extra-long power cords for easy setup.
Engineering and Design
The engineering and design of submersible water pumps can vary on make and model. They are available in stainless steel models, all thermoplastic models, or a combination of the two. Submersible pumps are engineered with one of two main designs for water intake. Some pump models feature a floating intake valve (extractor) made to intake water from just beneath the surface of the water. Submersible pump models with floating intakes are often more expensive but are made to supply the best quality water from the cistern. Other submersible water pumps feature intake screens on the body of the pump, so water is pumped directly from the location of the pump.
Specifications and Cost
Power ratings for submersible rainwater tank pumps range from low power 1/6 HP to strong 2 HP models. Common water pressure outputs for submersible water pumps can range from 11 PSI to 135 PSI. Flow rates can range up to 36 GPM and more and will depend on pump engine power, make, and model. Prices for submersible pumps will depend on features, manufacturing materials, and capabilities. Prices can range from $100+ to $1200+.
Further Considerations
There are a couple extra points to consider for submersible water pumps. First, submersible water pumps are often more expensive than other pump options. Second, submersible pumps many times also require what is known as a pump controller. A pump controller is a device that will automatically turn the pump on and off in response to changes in either pressure or water volume. While extremely useful in many rainwater applications, a pump controller adds on an extra cost to a submersible pump and additional setup if not already integrated into the product engineering.
Submersible water pumps advertised with integrated on/off and run-dry protection are models engineered with a built-in pump controller.
Always verify that a submersible water pump is intended for permanent installation. Some submersible pumps are labeled as utility pumps or sump pumps and are not designed for continuous use. While some utility pumps could serve as a cost-effective rainwater pump, many may not be suitable for rainwater setups. Sump pumps are not recommended for rainwater harvesting systems.
Booster Pumps / Jet Water Pumps
Booster pumps, also sometimes called jet water pumps, are electric powered, centrifugal-style water pumps. As their name perhaps indicates, booster pumps are capable of providing high flow rates and high pressures, and many times at values greater than those of the other water pump options. This pump type is sometimes also known simply as an aboveground water pump. The booster / jet water pump type should not be confused with transfer pumps that are designed for very high flow rates but low pressure.
Power Options
Booster pumps are commonly 115 volt electric powered for easy installation and use. Gas powered models are available that are capable of providing even greater pressures and flow rates. Electric powered booster pumps are sometimes designed to be hard-wired. Hard-wiring is more common in higher priced models, those with specialized pump-controller assemblies, and booster pumps and systems intended for handling large volumes of water as with whole-home, commercial, and agricultural scenarios.
Engineering and Design
Booster pumps are centrifugal-style water pumps meaning they use a high-velocity spinning impeller (think airplane rotor) to draw and push water through plumbing. It is this engineering design of centrifugal pumps that allows them to produce the higher flow rates and water pressures they are known for. When an application needs a high pressure or flow rate, such as for multiple activities, fixtures, or larger equipment, a booster pump is an ideal choice.
Specifications and Cost
Plumbing sizes for booster pumps range from small diameter 1/2 inch to larger 2 inch piping sizes. Booster pump specifications and outputs in PSI pressure, GPM flow rate, and total costs can vary significantly and will depend on brand, make, and model. Water pressure outputs for booster pumps range from 30 PSI to 145 PSI and up. Max flow rates can range from 12 GPM to 45 GPM and up. Prices can range from $350+ to $1200+.
Solar Powered Water Pumps
Solar powered water pumps are made to operate on the electrical current, volt, and wattage output that is commonly generated by photovoltaic (PV) solar panels. They are a low impact, high conservation, and green infrastructure option to provide the water pressures and flow rates needed for less intensive rainwater harvesting, plumbing distribution and use applications.
Power Options
Solar powered water pumps are specifically designed to receive the electrical power generated and put out from a PV solar panel. The power output from PV solar panels is often direct current (DC) and frequently either 12 volts or 24 volts. Therefore, many water pumps designed to operate on a 12 volt or 24 volt DC current could potentially work with a solar power electricity generation system.
Engineering and Design
Solar powered water pumps are often diaphragm style pumps. Diaphragm pumps are the preferred water pump style choice for solar power systems as the engineering and operational design of diaphragm pumps need less electrical power overall to operate compared to submersible, booster, and centrifugal style water pumps.
Specifications and Cost
Plumbing sizes, pressure outputs, and water flow rates for solar power water pumps are frequently similar to those of electric diaphragm pumps. The range of these specifications is also often on the lower side due to the lower wattage output common to typical PV systems, making solar powered water pumps best for smaller or singular outdoor applications such as lawn sprinklers, drip irrigation, and garden hoses. Common sizes include 5/8 inch and 1/2 inch. Max water pressure outputs can range from 35 to 55 PSI, and max flow rates from 1 GPM to 6 GPM. Prices can range from $90 to $300 and up.
Takeaways and Final Considerations
When looking for a water pump to use in rainwater harvesting, knowing the plumbing size, pressure and/or flow rates needed for the application or applications will help to select the best water pump for the job to be performed.
When considering water pump types and specifications, there are several different water pump types to choose that are suitable for rainwater harvesting systems and available in various specifications in engineering, design, and capabilities.
Water pumps are often listed with horsepower ratings to describe engine strength and the total power of the pump. Horsepower ratings for rainwater pumps commonly range from 1/6 HP up to 2 HP, with much more powerful pumps available to suit the needs of commercial, agricultural, and industrial applications. In general, a higher horsepower means stronger output capability in terms of water pressure and flow rate.
Water pumps are also available in various plumbing sizes to match an application needs and a water distribution system. Common inlet, outlet plumbing sizes for water pumps include 3/8 inch, 1/2 inch, 5/8 inch, 1 inch, 1.25 inch, and 2 inches. In general, larger plumbing sizes allow for higher GPM flow rates.
If you need further help or have further questions concerning water pumps or rainwater harvesting systems and setup, reach out to our professional, helpful team. You can also review our extensive collection of rainwater harvesting resources, articles, and guides here.