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For most home water systems, centrifugal pumps are the most commonly used type of water pump. They are widely used because they can move a steady amount of water efficiently through pipes, hoses, irrigation lines, and household plumbing.
In rainwater systems, the exact pump style depends on where the water is stored and how it will be used. An above-ground centrifugal pump is common for rain barrels, tanks, and cisterns that are easy to reach. A submersible pump, which sits underwater inside the tank, is also common for larger rainwater storage systems.
Why Centrifugal Pumps Are So Common
A centrifugal pump uses a spinning part called an impeller to move water. As the impeller turns, it pushes water from the pump inlet toward the outlet.
This design works well for many everyday jobs, including:
- Moving rainwater from a storage tank
- Supplying garden hoses
- Running drip irrigation or sprinklers
- Transferring water between tanks
- Supplying toilets or washing machines in properly designed non-potable systems
- Boosting water pressure around a property
Centrifugal pumps are especially useful when you need continuous water flow rather than very small, exact amounts of water.
The Most Common Pump Types for Rainwater Systems
"Centrifugal pump" describes how many pumps move water. Pumps using this basic design can be installed in several different ways.
Surface Pumps
A surface pump sits outside the water tank, usually on the ground or on a solid platform nearby.
The pump pulls water through an inlet pipe and pushes it toward the hose, irrigation system, or other outlet.
Surface centrifugal pumps work well when the pump can be placed close to the tank and does not need to lift water very far before it reaches the pump.
They are popular because they are usually easy to inspect and service. You do not have to remove the pump from the tank when it needs maintenance.
One important limitation is suction lift. A surface pump cannot pull water upward an unlimited distance. The greater the vertical distance between the water level and the pump, the harder the pump must work.
Submersible Pumps
A submersible pump operates while sitting underwater.
These pumps are often placed inside:
- Cisterns
- Underground tanks
- Large above-ground tanks
- IBC totes, when the specific pump and installation are suitable
Instead of pulling water toward itself through a long suction pipe, the pump pushes water out of the tank.
This can make submersible pumps useful when the storage tank is below ground or when suction problems would make a surface pump difficult to use.
Access is the main tradeoff. If the pump needs inspection or replacement, it usually has to be pulled out of the tank.
Never enter a cistern or other confined storage space to retrieve or service a pump. Confined spaces can contain serious hazards even when they appear safe from above.
Jet Pumps
Jet pumps are another form of centrifugal pump commonly used where water must be pulled from a source.
They are well known in well-water systems, but they can also appear in rainwater installations.
For a simple rain tank next to a garden, a standard surface centrifugal pump is often less complicated. A jet pump becomes more relevant when suction conditions or system design require it.
Booster Pumps
A booster pump is used mainly to increase pressure.
For example, gravity from a rain tank may provide enough water to fill a bucket but not enough pressure for a sprinkler or household fixture. A booster pump can raise that pressure.
Some booster systems include:
- A centrifugal pump
- A pressure switch or electronic controller
- A pressure tank
- Dry-run protection
The parts need to work together. Choosing a pump based only on its maximum pressure can lead to poor performance.
What Pump Is Best for a Rain Barrel?
For a basic rain barrel, the simplest option may actually be no pump at all.
If the barrel is raised above the garden, gravity may provide enough flow for:
- Filling watering cans
- Slow hose watering
- Some low-pressure drip irrigation
Gravity pressure is limited, however. A small height difference produces only a small amount of pressure.
If you need stronger hose flow or want to run irrigation equipment, a small centrifugal or suitable submersible pump may be more practical.
The pump should still be matched to the barrel outlet, hose size, required flow, and available power.
What Pump Is Best for a Larger Rainwater Tank?
For larger above-ground tanks, both surface and submersible centrifugal pumps are common.
A surface pump often makes sense when:
- The tank outlet is easy to reach
- The pump can sit close to the tank
- Easy maintenance is important
- Suction lift is small
A submersible pump often makes sense when:
- The tank is underground
- The water level is well below the pump location
- You want the pump hidden inside the tank
- Suction problems would be difficult to manage
Neither design is automatically better. The layout of the system matters more.
Flow Rate and Pressure Matter More Than Pump Type Alone
Knowing that you need a centrifugal pump is only the first step.
The pump must also provide enough flow rate and pressure.
Flow rate tells you how much water the pump can move during a certain amount of time. It may be shown in gallons per minute, liters per minute, or another unit.
A garden hose may need much less water than several sprinklers running at once.
Pressure describes how strongly the pump pushes the water through the system.
A pump that provides plenty of flow at low pressure may still perform poorly with equipment that requires higher pressure.
Pump specifications should be checked at the pressure or head height your system actually requires, not just at the pump's advertised maximum flow.
What Is Head Height?
Head height describes the resistance the pump must overcome to move water through the system.
Vertical lift is part of it, but it is not the whole story.
The pump must also overcome resistance from:
- Long pipes
- Small-diameter pipes
- Elbows
- Valves
- Filters
- Check valves
- Irrigation equipment
This is why a pump rated for a high flow under ideal conditions may deliver much less water once connected to a real system.
Pump Connections Must Match the System
Use commonly used water-transfer pumps to verify suction-pipe constraints and protective shutoffs.
Before buying or installing a pump, check how it will connect to the tank and downstream plumbing.
Look at:
- Pump inlet size
- Pump outlet size
- Tank outlet size
- Pipe or hose diameter
- Thread type
- Required adapters
- Valves
- Filters or strainers
For example, connecting a large pump to a very small tank outlet can restrict flow before water even reaches the pump.
IBC totes can require extra attention because their factory valves and threads are not always the same as standard household plumbing fittings. An adapter may be needed between the tote valve and the pump plumbing.
Protect the Pump From Debris
Rainwater can carry leaves, roof grit, insects, sediment, and other material into storage.
Keeping larger debris out of the pump helps reduce clogging and wear.
A rainwater system may use several stages before the pump, such as:
- Gutter screens
- Leaf guards
- A first-flush device
- Tank inlet screens
- Pump strainers
A first flush diverts some of the initial roof runoff during a rain event. This early runoff can contain a higher amount of dirt and debris that accumulated on the roof.
Prefiltration does not make roof runoff safe to drink. It mainly helps keep debris out of storage and downstream equipment.
Dry-Run Protection Is Important
Many water pumps rely on moving water for cooling or lubrication.
If the tank runs empty while the pump continues operating, the pump can overheat or become damaged.
A rainwater pump system may use:
- A float switch
- A low-level sensor
- An electronic pump controller
- Built-in dry-run protection
The protection method must be compatible with the pump and electrical system.
For an automatic rainwater system, dry-run protection is usually much safer than depending on someone to notice when the tank is empty.
Pump Location Affects Performance
Keep the distance between the storage tank and pump as practical for the system design.
Surface pumps generally work better when the suction pipe is:
- Short
- Properly sized
- Airtight
- Free of unnecessary bends
Even a small air leak on the suction side can cause poor priming, weak flow, or loss of suction.
Submersible pumps avoid many suction problems because they are already surrounded by water.
Think About Electricity and Outdoor Conditions
Most household rainwater pumps use electricity, so water and electrical safety need to be considered together.
Outdoor pumps and controls must be suitable for their location and protected as required by the manufacturer and applicable electrical rules.
Extension cords, improvised wiring, and electrical connections exposed to rain can create serious hazards.
Have a qualified electrician handle wiring or electrical work beyond simple manufacturer-approved plug-in equipment.
Freezing Weather Changes the Setup
A pump that works well during summer may be damaged if water freezes inside it.
In freezing climates, exposed components may include:
- Pumps
- Pipes
- Filters
- Valves
- Pressure tanks
- Hoses
Some systems are winterized and shut down. Others are installed in protected locations and designed for cold-weather operation.
Do not assume insulation alone will keep a pump or pipe from freezing.
What About Pumps for Drinking Water?
A pump does not make rainwater drinkable.
If collected rainwater will be used as drinking water, the pump is only one part of a much larger system.
Potable means water that is suitable for drinking. Making roof-collected rainwater potable can involve suitable collection materials, debris control, storage management, treatment stages, current laboratory testing, maintenance, and compliance with applicable local requirements.
The pump and every component that contacts treated drinking water must also be appropriate for that use.
A single filter, UV unit, purifier, test strip, or water-quality meter cannot by itself establish that roof runoff is safe to drink.
For potable rainwater systems, professional system design and current local health guidance are especially important.
Choosing Between a Surface and Submersible Pump
A simple comparison can narrow the choice.
| Situation | Often Suitable |
|---|---|
| Small above-ground tank near the garden | Surface centrifugal pump |
| Pump needs easy maintenance access | Surface centrifugal pump |
| Underground cistern | Submersible pump |
| Long or difficult suction lift | Submersible pump |
| Low-pressure gravity system needs stronger pressure | Booster pump system |
| Basic rain barrel used for watering cans | Gravity may be enough |
The final choice should still be based on required flow, pressure, vertical lift, pipe size, power supply, and the pump manufacturer's operating limits.
Frequently Asked Questions
What is the most commonly used water pump?
The centrifugal pump is one of the most commonly used water pumps for homes, gardens, irrigation, water transfer, and rainwater systems. It uses a spinning impeller to move water.
Is a submersible pump a centrifugal pump?
Many submersible water pumps use centrifugal pumping mechanisms. "Submersible" mainly describes where the pump operates: underwater.
Is a surface pump or submersible pump better for rainwater?
It depends on the tank and plumbing layout. Surface pumps are easier to access and often work well beside above-ground tanks. Submersible pumps are often useful for underground tanks or situations with difficult suction lift.
Do I need a pump for a rain barrel?
Not always. A raised rain barrel can supply water using gravity. A pump becomes useful when you need more flow or pressure than gravity can provide.
Can a rainwater pump run a sprinkler?
It can if the pump provides enough flow and pressure for the sprinkler. Check the sprinkler's requirements and compare them with the pump's performance at the actual head and pipe resistance in your system.
What happens if a water pump runs when the tank is empty?
Some pumps can overheat or become damaged when they run without enough water. A float switch, low-water sensor, or compatible dry-run controller can help prevent this.
Does pumping rainwater make it safe to drink?
No. A pump only moves water. Drinking-water safety requires an appropriate collection, storage, treatment, testing, and maintenance system that meets applicable local requirements.
