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Water pumps move water from one place to another or create pressure so water can flow through pipes, hoses, filters, and irrigation systems. For most home and rainwater systems, pumps can be grouped into four useful types: centrifugal pumps, submersible pumps, jet pumps, and positive displacement pumps.
The right type depends on where the water is stored, how far it must move, how high it must be lifted, and how much pressure and flow you need.
The Four Main Types of Water Pumps
| Pump type | Where it works | Common uses |
|---|---|---|
| Centrifugal | Usually outside the water | Tanks, irrigation, water transfer |
| Submersible | Underwater inside a tank or well | Cisterns, wells, rainwater systems |
| Jet | Above the water source | Wells and tanks where suction is needed |
| Positive displacement | Usually outside the water | Precise flow, high pressure, special applications |
These categories cover many of the pumps homeowners are likely to encounter. Individual pumps may use different designs within each category.
1. Centrifugal Pumps
A centrifugal pump uses a spinning part called an impeller to move water.
Water enters near the center of the impeller. As the impeller spins, it pushes the water outward and into the pump outlet.
Centrifugal pumps are common because they can move a large amount of water with a fairly simple design.
They are often used for:
- Moving rainwater from one tank to another
- Garden irrigation
- Sprinkler systems
- Household non-potable water supply
- Filling or draining tanks
- Increasing water pressure
Most centrifugal pumps sit outside the water source.
Advantages
Centrifugal pumps are usually well suited to steady water movement. Many models can provide both useful flow and moderate pressure.
They can also be easier to inspect and service than pumps sitting inside a tank.
Limitations
Many centrifugal pumps need to be primed before they can pump.
Priming means filling the pump and suction pipe with water so the pump is not trying to move air.
They also have limits on how far they can pull water upward through a suction line. Long, narrow, leaking, or poorly installed suction pipes can greatly reduce performance.
A centrifugal pump should not be allowed to run dry unless it is specifically designed for that condition.
2. Submersible Pumps
A submersible pump operates while completely or partly underwater.
Instead of pulling water toward itself through a long suction pipe, the pump pushes water from inside the tank, cistern, sump, or well.
This makes submersible pumps a common choice for rainwater storage systems.
They are used in:
- Underground cisterns
- Above-ground rainwater tanks
- Wells
- Sumps
- Drainage systems
- Irrigation systems
- Cabin water systems
Advantages
Because the pump is already surrounded by water, priming is generally not an issue during normal operation.
Submersible pumps can also be quieter because the tank and water help contain pump noise.
They can work well when the storage tank is below the point where the water will be used.
Limitations
Access can be less convenient.
If the pump needs cleaning, inspection, or replacement, it may have to be pulled out of the tank or well.
Electrical connections must also be suitable for the application. Pumps, cables, controls, and connections used around water should be installed according to their instructions and applicable electrical requirements.
Sediment can shorten pump life. Rainwater systems often benefit from keeping leaves, grit, and settled debris away from the pump inlet.
3. Jet Pumps
A jet pump sits above the water source and uses suction to lift water into the pump.
They are especially common with wells, although they can also be used with storage tanks.
There are several jet-pump arrangements. Some are intended for relatively shallow water sources, while others use additional components in the well to work at greater depths.
Advantages
The pump itself remains above ground, making it easier to reach for inspection or repair.
A properly sized jet pump can provide useful household water pressure.
Limitations
Jet pumps depend heavily on the suction side of the system.
Problems can occur from:
- Air leaks
- Poor priming
- Long suction pipes
- Excessive lift
- Restricted fittings
- Clogged screens
- Low water levels
They may also be noisier than a submersible pump.
For a rainwater tank located close to the pump and at roughly the same elevation, a centrifugal or submersible pump is often simpler.
4. Positive Displacement Pumps
A positive displacement pump moves a fixed amount of water during each pumping cycle.
Instead of relying mainly on a spinning impeller, it traps water and physically pushes it through the pump.
Common designs include diaphragm, piston, gear, and rotary pumps.
Small diaphragm pumps are especially common in:
- RV water systems
- Cabins
- Small rainwater systems
- Sprayers
- Misting systems
- Low-flow pressure systems
Advantages
Positive displacement pumps can often produce relatively high pressure even at lower flow rates.
Some types are also good at self-priming.
That can make them useful where water demand is small but reliable pressure is important.
Limitations
They may produce less water flow than a similarly sized centrifugal pump.
Some designs create pulses rather than perfectly smooth flow. A pressure tank or accumulator may be used to reduce these pressure changes.
Because positive displacement pumps can build substantial pressure, the plumbing and controls must be designed for the pump's output.
Which Type Is Best for a Rainwater System?
For most rainwater harvesting systems, the main choice is between a centrifugal pump and a submersible pump.
A submersible pump often makes sense when the water is stored in a cistern or large tank and you want the pump hidden inside the storage vessel.
An external centrifugal pump can make sense when the tank outlet is easy to reach and you want convenient access to the pump for maintenance.
Small positive displacement pumps can work well for cabins, small garden systems, or other applications with modest water demand.
Jet pumps are more commonly associated with wells, though they can be useful when the system requires an above-ground pump to lift water from below.
Flow Rate and Pressure Matter More Than Pump Type Alone
For a suitable water pumps for irrigation systems, first understand inlet conditions needed to protect the pump.
Choosing the right category is only the beginning.
A pump also has to provide enough flow rate and pressure for the intended use.
Flow rate is the amount of water the pump can move in a certain amount of time, such as gallons per minute.
A garden hose may need much less water than several irrigation zones running at once.
Pressure becomes important when water must pass through:
- Long pipes
- Small pipes
- Filters
- Valves
- Sprinklers
- Drip-system regulators
- Fixtures
Each restriction creates resistance to water flow.
A pump that moves plenty of water through an open hose may produce much less flow after filters and long pipe runs are added.
Understand Head Height
Pump specifications often refer to head or head height.
Head describes the amount of resistance the pump must overcome, expressed as a height of water.
Vertical lift is one part of the calculation.
For example, pumping water from a ground-level tank to an irrigation line higher up a hill requires more head than moving water between two tanks at the same elevation.
Pipe friction, fittings, filters, valves, and other restrictions also add to the total load on the pump.
Do not choose a pump based only on its maximum flow rating. Maximum flow is commonly measured under conditions with very little resistance.
The useful question is how much flow the pump can provide at the head your system actually creates.
Consider Where the Pump Will Be Installed
Pump location can narrow the choices quickly.
If the pump will sit inside a cistern, you need a pump designed for submersible operation.
If it must remain outside the tank, an external centrifugal, jet, or positive displacement pump may be appropriate.
Also consider whether the area is:
- Exposed to rain
- Subject to flooding
- Below freezing
- Hard to access
- Close to living spaces
- Far from electrical power
Follow the manufacturer's requirements for weather protection, ventilation, wiring, mounting, and operating conditions.
Protect the Pump From Running Dry
Running a pump without enough water can damage many pump types.
This can happen when:
- A rainwater tank empties
- The suction line loses prime
- An inlet becomes blocked
- A valve is accidentally closed
- The water level drops below the pump intake
For systems where an empty tank is possible, consider suitable low-water or dry-run protection.
A float switch, level sensor, pump controller, or built-in protection system may be used depending on the equipment.
Do not assume that every pump automatically shuts itself off when the tank runs dry.
Keep Sediment Away From the Pump
Rainwater can carry dirt, roofing particles, organic matter, insects, and other debris into storage.
Good collection design helps keep this material away from the pump.
Depending on the system, that may include:
- Gutter screens
- Leaf screens
- First-flush diversion
- Calming inlets
- Floating pump intakes
- Appropriate strainers
- Routine tank maintenance
A first flush device diverts some of the initial roof runoff at the start of a rain event. This first runoff can contain a higher concentration of debris that accumulated on the roof between rains.
Prefiltration can help protect pumps and downstream equipment, but it does not by itself make rainwater safe to drink.
Check the Pipe and Connection Sizes
A good pump can perform poorly when connected to restrictive plumbing.
Check the required inlet and outlet sizes before choosing fittings, hoses, valves, or filters.
The suction side of an external pump deserves particular attention. Undersized suction pipe, unnecessary elbows, restrictions, or air leaks can cause poor performance and pump problems.
Tank outlets may use threaded fittings or bulkhead fittings.
A bulkhead fitting passes through the tank wall and creates a sealed connection for attaching pipe or valves.
Make sure thread type, pipe diameter, pump ports, and tank fittings can actually connect before buying or assembling the system.
Pumps Do Not Make Rainwater Safe to Drink
A water pump only moves water. It does not make roof runoff potable.
Potable means suitable for drinking.
Non-potable water is water that is not intended for drinking and may be used for purposes such as irrigation or toilet flushing where allowed.
If collected rainwater is being considered for drinking, the whole system needs to be evaluated. Collection surfaces, storage, contamination control, treatment stages, maintenance, current laboratory testing, and local requirements can all matter.
A pump should be selected as one part of that system, not treated as water treatment equipment.
Choosing Between the Four Pump Types
A simple starting point is:
- Choose a centrifugal pump for general tank transfer or irrigation where an external pump works well.
- Choose a submersible pump when the pump can sit inside a tank, cistern, or well.
- Choose a jet pump when an above-ground pump must draw water from a well or lower water source.
- Choose a positive displacement pump when you need smaller flows, reliable pressure, or a self-priming design suited to the application.
Then check flow, pressure, total head, pipe size, power supply, controls, water level, sediment exposure, and freeze conditions before choosing a specific pump.
Frequently Asked Questions
What is the most common type of water pump?
Centrifugal pumps are among the most widely used pumps for moving water. They are used in irrigation, water transfer, pressure systems, and many other applications.
What type of pump is best for a rainwater tank?
Both external centrifugal pumps and submersible pumps can work well. A submersible pump is often convenient for a large tank or cistern, while an external pump can be easier to reach for maintenance. The best choice depends on tank location, required flow, pressure, head height, and plumbing layout.
What is the difference between a centrifugal pump and a submersible pump?
"Centrifugal" describes how many pumps move water, while "submersible" mainly describes where a pump operates. In fact, many submersible water pumps use a centrifugal pumping mechanism. In household discussions, however, external centrifugal pumps and submersible pumps are often treated as separate practical categories because their installation is very different.
Can a water pump pull water uphill?
An above-ground pump may be able to lift water through its suction line, but suction lift is limited. A submersible pump pushes water upward instead. The total vertical rise and pipe resistance must stay within the pump's operating range.
Can I connect a pump directly to a rain barrel?
Sometimes, but the pump must be suitable for the available water supply and intended use. Small rain barrels can empty quickly with a high-flow pump. The outlet size, fittings, pump inlet requirements, dry-run protection, and sediment control also need to be considered.
Does a bigger water pump give more pressure?
Not automatically. Pump performance depends on its design and operating curve. A pump may be designed for high flow at lower pressure or lower flow at higher pressure. Choose a pump according to the required flow and total head rather than motor size alone.
Do water pumps need pressure tanks?
Not all systems do. Pressure tanks are commonly used where a pump supplies fixtures or other intermittent demand. They can reduce rapid pump cycling and help stabilize pressure. Simple transfer pumps and some irrigation systems may not require one.
