As an affiliate, we may earn a commission from qualifying purchases. We get commissions for purchases made through links on this website from Amazon and other third parties.
For a residential rainwater system, Grundfos is one of the best all-around aftermarket water pump brands. It has pumps made for rainwater tanks, garden irrigation, pressure boosting, and household water supply. The company also provides pump sizing tools, service information, and replacement parts.
That does not mean Grundfos is always the right choice. Davey can be a better fit for dedicated rainwater-tank systems, especially where its rainwater controls and service network are common. Goulds Water Technology is another strong choice for traditional jet, centrifugal, booster, and submersible pump systems.
The best pump is the one that matches your tank, plumbing, required flow, pressure, lift, electrical supply, and intended water use.
Best Aftermarket Water Pump Brands for Rainwater Systems
As of September 2026, these are three established brands worth considering for residential rainwater and water-storage systems.
| Brand | Best Fit | Main Strength |
|---|---|---|
| Grundfos | Most residential rainwater systems | Broad range of submersible and pressure-boosting pumps |
| Davey | Rainwater tanks and household pressure systems | Strong focus on rainwater management and pump controls |
| Goulds Water Technology | Conventional pump and pressure systems | Wide choice of jet, centrifugal, booster, and submersible pumps |
These are not interchangeable choices. A good brand can still be a bad purchase if the pump is the wrong size or type.
Why Grundfos Is a Good All-Around Choice
Grundfos has several pump types that fit common rainwater systems.
Its SB and SBA submersible booster pumps are designed to sit inside a tank or well. Grundfos specifically lists rainwater harvesting, garden irrigation, and pressure boosting from storage tanks among their applications.
The company also offers surface-mounted pressure boosters. Its SCALA pumps can draw from storage tanks and boost water pressure for household or outdoor uses. Grundfos lists rainwater tanks among the suitable water sources for these systems.
This gives you several ways to build a system.
For example:
- A submersible pump can sit inside a cistern and push water to the garden.
- A surface pump can sit beside an above-ground tank.
- A pressure booster can supply toilets, outdoor faucets, or other approved household uses.
- A variable-speed pump can maintain steadier pressure as water demand changes.
Grundfos also publishes service-part information for some pump ranges. That can matter if you plan to keep a system for many years.
When Davey May Be the Better Choice
Davey is especially worth considering when you want a system designed around rainwater storage.
The company groups several pumps and controls under rainwater management and provides equipment for home pressure, irrigation, water transfer, and rainwater tanks.
Davey also makes rainwater control systems that can manage the change between stored rainwater and another water source. These systems are useful in locations where local plumbing rules allow this type of connection and where the installation is completed correctly.
Davey's pump range includes:
- Surface pressure pumps
- Multistage pumps
- Transfer pumps
- Submersible pumps
- Automatic pump controllers
- Constant-pressure systems
- Rainwater management controls
Davey is particularly established in Australia and nearby markets, so local dealer and service availability can make it a very practical choice there.
Do not choose a pump only because the brand has a strong reputation. Check whether replacement controllers, seals, pressure tanks, and service technicians are readily available where you live.
When Goulds Water Technology Makes Sense
Goulds Water Technology is a good option when you are building a more traditional pump system rather than buying an all-in-one rainwater package.
Its residential range includes jet pumps, centrifugal pumps, pressure boosters, submersible pumps, pressure tanks, and pump controls.
Jet pumps can work well for some above-ground tanks and shallow suction applications. Submersible pumps are useful when placing the pump inside the water storage tank makes more sense.
Goulds also provides pump selection and sizing tools.
That matters because choosing a pump by horsepower alone is a common mistake.
Brand Matters Less Than Pump Sizing
A high-quality pump that is badly sized can perform worse than a less expensive pump that correctly matches the system.
You need to know two main numbers:
Flow Rate
Flow rate is how much water the pump can deliver during a certain amount of time.
It may be shown as:
- Gallons per minute (GPM)
- Liters per minute (L/min)
- Cubic meters per hour (m³/h)
A drip irrigation line may need little flow. Several sprinklers running together may need much more.
Household fixtures can create even higher peak demand when several outlets run at once.
Head Height
Head height describes how much resistance the pump must overcome.
It includes more than vertical height.
The pump has to overcome:
- Vertical lift
- Pipe friction
- Filters
- Valves
- Fittings
- Long pipe runs
- Required outlet pressure
Suppose your tank is near the house but the garden is 100 feet away and uphill. The pump has to overcome both elevation and pipe resistance.
This is why comparing pumps only by their maximum flow number can be misleading.
A pump produces less flow as the required head increases.
Check the Pump Curve Before Buying
A pump curve shows how much water a pump can provide at different head heights.
This is one of the most useful specifications on a pump data sheet.
Do not size your system from:
- Maximum flow alone
- Maximum pressure alone
- Horsepower alone
Maximum flow is normally measured under very low resistance. Maximum head occurs when flow approaches zero.
Your actual system operates somewhere between those two points.
Find the approximate flow and head your system needs. Then check whether the pump can supply both at the same time.
Surface Pump or Submersible Pump?
Both designs can work well with rainwater.
Choose a Surface Pump When
A surface pump may make sense when:
- The tank outlet is close to the pump.
- The pump can stay protected from weather.
- Maintenance access is important.
- You want the motor outside the tank.
- The water level does not create excessive suction lift.
Surface pumps must pull water toward the pump before pushing it downstream.
Air leaks on the suction side can cause trouble. Long or undersized suction pipes can also reduce performance.
Choose a Submersible Pump When
A submersible pump sits inside the water.
It can be a good choice when:
- You have a large cistern.
- The tank is underground.
- You want quieter operation.
- Suction problems would otherwise be difficult.
- The pump needs to push water a significant distance.
Grundfos, for example, specifically markets its SB and SBA submersible pumps for rainwater harvesting and pressure boosting from tanks.
Access matters, however. Pulling a pump from an underground cistern for inspection can be more work than servicing a surface pump.
Check the Connections Before Replacing a Pump
Do not assume a new pump will connect directly to the old plumbing.
Details about comparing brand of pump options help verify available inlet head and safe operating controls.
Check:
- Inlet size
- Outlet size
- Thread type
- Pipe diameter
- Existing check valve
- Pressure tank
- Pump controller
- Filters
- Electrical connection
- Voltage and frequency
A reduction fitting can make two pipe sizes physically connect, but that does not mean the smaller plumbing can handle the required flow.
Very small suction piping can be especially troublesome.
Look for Dry-Run Protection
Running without enough water can damage many pumps.
This can happen when:
- The tank empties.
- The intake becomes blocked.
- A valve is accidentally closed.
- A suction pipe loses its prime.
- An intake float gets stuck.
Dry-run protection shuts down or protects the pump when adequate water is not available.
Some modern pump systems include this feature. Grundfos, for example, lists dry-running protection on its SCALA2 booster.
If your pump does not provide suitable protection internally, an external tank-level switch or pump controller may be needed.
Think About Sediment Before Choosing a Pump
Roof runoff can contain grit, leaves, insects, organic debris, and fine sediment.
Most household pressure pumps are not designed to act as debris grinders.
Keep larger material out of the storage tank with suitable collection and prefiltration. A floating intake can also help draw water away from sediment that has settled near the tank bottom.
Grundfos warns that sand and other impurities can cause pump wear or blockage and recommends suitable inlet filtration or a floating strainer for the SCALA2.
Do not install an extremely restrictive filter ahead of a pump without checking the pump manufacturer's requirements. Excessive suction restriction can create its own problems.
Consider Parts and Local Service
A pump may last many years, so buying the pump is only part of the decision.
Check whether you can obtain:
- Mechanical seals
- O-rings
- Controllers
- Pressure sensors
- Pressure tanks
- Check valves
- Replacement motors
- Authorized service
A brand with excellent specifications but no support in your area may be less practical than another established brand with a nearby dealer.
This is one reason the "best" brand can vary by country.
Do Not Oversize the Pump
A larger pump is not automatically better.
An oversized pump can cause:
- Rapid cycling
- Excess pressure
- More noise
- Higher electrical load
- Unnecessary stress on fittings
- Poor operation with small irrigation zones
A pressure tank, variable-speed controller, or correctly sized irrigation zones can help manage changing demand, but the pump should still be selected around the expected operating range.
Match the Pump to the Intended Water Use
The system for watering vegetables does not have the same requirements as a system supplying a house.
Garden Irrigation
Focus on:
- Required sprinkler or drip flow
- Elevation
- Pipe length
- Irrigation pressure
- Automatic controls
A surface or submersible rainwater pump can both work.
Tank-to-Tank Transfer
Pressure may matter less.
The main concern is often moving the required amount of water through the pipe without exceeding the pump's operating limits.
Household Non-Potable Supply
Toilets, laundry, and other locally permitted uses may require stable pressure and automatic operation.
Local plumbing rules can also require separation from potable plumbing or approved backflow protection.
Drinking-Water Systems
A good pump does not make collected rainwater safe to drink.
Potable means water considered suitable for drinking.
Using harvested rainwater as drinking water is a whole-system water-quality issue involving suitable collection, contamination control, treatment, maintenance, current laboratory testing, and applicable local requirements.
Pump selection is only one part of that system.
Which Brand Should You Choose?
For most homeowners looking for a replacement or aftermarket pump for a rainwater system, Grundfos is a strong first brand to consider because it offers both tank-mounted submersible pumps and integrated pressure-boosting systems specifically suited to rainwater applications.
Choose Davey when rainwater management equipment, automatic controls, and local Davey service are especially strong in your area.
Choose Goulds Water Technology when you want a conventional jet, centrifugal, booster, or submersible pump system and have good local access to its pumps and service.
But make the final decision from the pump curve and your system requirements.
The right order is:
- Decide what the water will supply.
- Calculate the needed flow.
- Estimate the required head and pressure.
- Choose surface or submersible installation.
- Check voltage and electrical requirements.
- Check inlet and outlet connections.
- Check dry-run and pressure controls.
- Compare suitable pumps from established brands.
- Confirm that parts and service are available locally.
That approach is much more reliable than choosing a pump because one brand is commonly called "the best."
Frequently Asked Questions
What is the best aftermarket water pump brand for a rainwater tank?
Grundfos is a strong all-around choice for residential rainwater systems. Davey is also a strong option, particularly for dedicated rainwater management and household pressure systems. The final choice should be based on flow, head, pressure, connections, controls, and local service availability.
Is Grundfos better than Davey?
Neither brand is best for every installation. Grundfos has a broad range of submersible and integrated booster pumps suited to rainwater systems. Davey has a strong range of rainwater management, pressure, and pump-control equipment. Local parts and service can be the deciding factor.
How much horsepower should a rainwater pump have?
Do not select a rainwater pump from horsepower alone. First determine the required flow rate and total head. Then use the manufacturer's pump curve to find a pump that provides the required flow at that head.
Is a submersible pump better for a rainwater tank?
A submersible pump can be an excellent choice for a cistern or large rainwater tank because it pushes water rather than drawing it through a suction line. A surface pump may be easier to inspect and service. Tank design, access, elevation, and required pressure should determine the choice.
Can I replace my existing rainwater pump with another brand?
Often you can, but it may not be a direct replacement. Check the pump's voltage, flow, head, inlet and outlet sizes, thread type, controller, pressure tank, check valves, and electrical requirements before changing brands.
Does a rainwater pump need dry-run protection?
Dry-run protection is highly useful because a rainwater tank can eventually run low or empty. Some pumps include this protection. Other systems use a separate float switch, level sensor, or pump controller.
Will a better water pump make rainwater safe to drink?
No. A pump only moves water. It does not establish that roof-collected rainwater is safe to drink. Drinking-water use requires a suitable collection and treatment system, proper maintenance, current water testing, and compliance with applicable local requirements.
