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A water pump does not always need a check valve, but many pump systems do.
A check valve is a one-way valve. It lets water move toward the outlet but stops it from flowing backward when the pump shuts off.
Whether you need one depends on the pump type, where the pump sits, and how the plumbing is arranged.
When a Water Pump Usually Needs a Check Valve
A check valve is commonly used when backward flow would cause the system to lose pressure, lose prime, drain a pipe, or make the pump cycle more often.
Common examples include:
- Pumps drawing water up from a tank, cistern, or well
- Pressure systems with a pressure tank
- Long irrigation lines that could drain backward
- Pumps installed above the water source
- Systems where water could siphon back into a rainwater tank
- Multiple pumps or water sources connected to the same plumbing
The valve is normally installed so water can flow in the intended direction while reverse flow is blocked.
Why Check Valves Matter
When a pump stops, water in the pipe may naturally try to move backward.
That can create several problems.
The pump may lose its prime
Some surface pumps need their suction line and pump housing to stay full of water.
If water drains back into the source after every pump cycle, the pump may lose its prime. The next time it starts, it may struggle to move water or run dry.
A properly placed check valve can help keep that water from draining backward.
A pressure tank may lose pressure
In a pressurized water system, the pump fills the pressure tank and raises system pressure.
Without a check valve where one is required, stored water can flow backward through the pump after it stops. Pressure may drop even when nobody is using water.
That can make the pump restart repeatedly.
Pipes may drain after each cycle
An irrigation or transfer line may partially empty when the pump shuts off.
That means the pump must refill the line every time it starts. You may notice:
- Delayed water delivery
- Air coming from outlets
- Pressure fluctuations
- More frequent pump operation
A check valve can keep the line full when the system design allows it.
Does a Rainwater Pump Need a Check Valve?
Many rainwater pump systems use one, but the correct location depends on the setup.
Consider a basic system:
Rainwater tank → suction pipe → pump → pressure plumbing
If the pump is above the water level in the tank, keeping the suction line full becomes especially important.
A check valve may be installed at or near the end of the suction line. When a check valve is placed at the submerged intake, it is often called a foot valve.
A foot valve normally combines:
- A one-way check valve
- An intake screen or strainer
The valve helps keep the suction pipe full when the pump stops. The screen helps keep larger debris out of the pipe.
A pump drawing from the bottom outlet of an above-ground rain barrel or IBC tote may have different needs because gravity can keep the pump inlet flooded.
Pumps Below the Water Level May Be Different
If the pump inlet sits below the normal water level of the tank, water naturally flows toward the pump by gravity.
This is called a flooded suction arrangement.
Such systems may not need a suction-side check valve solely to maintain prime.
A check valve may still be useful somewhere else in the system if it needs to:
- Hold pressure
- Prevent reverse siphoning
- Stop water from another source flowing backward
- Prevent a discharge pipe from draining
Do not add valves simply because more valves seem safer. Every valve creates some resistance to water flow.
Some Pumps Already Have a Check Valve
Many pumps or pump controllers include an internal non-return valve.
If your pump already has one, adding another nearby may be unnecessary and can sometimes create problems.
Check the pump manual before installing an extra valve.
Manufacturers may specify:
- Whether an external check valve is needed
- Which side of the pump it belongs on
- Minimum distance from the pump
- Required valve size
- Whether multiple check valves should be avoided
The internal design of the pump matters more than a general plumbing rule.
Check Valve on the Suction Side
A suction-side check valve is mainly used to keep water from draining away from the pump.
This is especially common with surface pumps that lift water from a source below them.
For example:
Underground cistern → foot valve → suction pipe → surface pump
When the pump stops, the foot valve closes. The suction line stays filled instead of emptying back into the cistern.
This makes restarting easier and reduces the chance of losing prime.
Suction-side restrictions matter
The suction side of a pump is sensitive to restrictions.
An undersized check valve, clogged screen, tight fitting, or excessive pipe length can reduce available flow to the pump.
Use a valve that matches the pipe and pump requirements rather than reducing the pipe size just to fit a valve.
Leaks on the suction side are also important. A connection can pull air into the pipe without visibly leaking water out.
Check Valve on the Discharge Side
A check valve may also be installed after the pump.
A common arrangement is:
Tank → pump → check valve → pressure tank → fixtures
The purpose is usually to stop pressurized water from moving backward through the pump.
However, the correct layout depends on the pump and pressure-control design. Some pumps have their required check valve built in.
Follow the manufacturer's plumbing diagram when using a pressure switch, pressure tank, electronic controller, or variable-speed pump.
Do Submersible Pumps Need Check Valves?
Many submersible pump systems use check valves.
A submersible pump sits underwater and pushes water up the discharge pipe.
A check valve can prevent the water column above the pump from falling backward every time the pump stops.
Some submersible pumps contain a built-in check valve. Others require an external one.
Long vertical pipes may involve special valve placement requirements because a large moving column of water can create pressure changes when the pump starts or stops.
For deep wells or large cistern systems, follow the pump manufacturer's instructions rather than adding several check valves without a design reason.
Does a Pump With a Pressure Tank Need a Check Valve?
Reviewing common problems with check valves helps compare upkeep requirements that affect future reliability.
Usually, some form of backflow prevention is needed so pressure stored in the tank does not escape backward through the pump.
The valve may be:
- Built into the pump
- Installed near the pump outlet
- Part of the well or suction assembly
Its exact position depends on the system.
If pressure falls when no water is being used, a leaking check valve is one possible cause. Other possibilities include:
- Plumbing leaks
- A leaking toilet or fixture
- A damaged pressure tank
- A leaking foot valve
- A pump-controller problem
Do not assume the check valve is responsible until the rest of the system has been checked.
Can You Install More Than One Check Valve?
Sometimes, but more is not automatically better.
Multiple check valves may be needed in large or specialized systems. In a simple household rainwater setup, unnecessary valves can add resistance and make troubleshooting harder.
Two valves can also trap pressure between them.
If the trapped water heats up and expands, pressure can rise in that isolated section of pipe. System design may need to account for that.
Use additional check valves only when the pump manufacturer or system design calls for them.
How to Choose the Right Check Valve
The valve must fit both the plumbing and the operating conditions.
Match the pipe size
Avoid creating an unnecessary restriction on the pump inlet or outlet.
A valve should normally match the relevant pipe size unless the pump design specifies otherwise.
Check the flow direction
Check valves usually have an arrow on the body.
The arrow must point in the direction water is supposed to travel.
Installing the valve backward can block flow completely.
Consider opening resistance
A check valve needs some pressure difference before it opens.
This is sometimes called cracking pressure.
A valve with high opening resistance may be a poor choice for a low-pressure gravity-fed system or a sensitive suction line.
Use suitable materials
The valve material should be compatible with:
- The water being moved
- Pipe material
- Outdoor exposure
- Expected pressure
- Expected temperature
For drinking-water systems, every component in contact with the water should also be suitable for that intended use.
Collected rainwater should not be considered potable simply because the pump, valve, or piping uses drinking-water-rated materials.
Common Signs of a Bad Check Valve
A check valve can wear out, clog, stick, or collect debris.
Possible symptoms include:
- Pump loses prime after sitting
- Pump starts when no water has been used
- Pressure drops after the pump shuts off
- Water drains backward into the tank
- Long delay before water reaches an outlet
- Pump repeatedly cycles on and off
- Water hammer or unusual pipe noises
These symptoms can have other causes, so inspect the entire system before replacing parts.
Check Valves Need Maintenance Too
A check valve is a moving mechanical part.
Rainwater systems can carry small amounts of grit, organic material, insects, roof debris, or sediment that passed earlier screens.
That material can keep a valve from sealing completely.
Periodic system maintenance should include checking accessible valves for:
- Debris
- Mineral buildup
- Damaged seals
- Corrosion
- Restricted movement
- Leaking threaded connections
A submerged foot valve may also have a strainer that needs cleaning.
Avoid Putting a Check Valve Where It Creates a Problem
A poorly placed valve can make a pump system worse.
Be cautious if a proposed valve would:
- Significantly restrict the suction line
- Trap pressure between closed valves
- Prevent proper pressure-switch sensing
- Conflict with an electronic pump controller
- Block required drainage for winterizing
- Make freeze protection harder
- Interfere with the manufacturer's required layout
In freezing climates, remember that a check valve can keep a pipe full of water that would otherwise drain. Trapped water can freeze and damage the valve or piping.
Plan winter drainage before deciding where the valve belongs.
A Simple Rule for Rainwater Systems
Think about what happens when the pump stops.
If water can flow backward and that backward movement would make the pump lose prime, drain the system, or release stored pressure, a check valve is probably needed somewhere in the design.
Then check the pump manual to determine whether the pump already has one and where any additional valve should go.
For a simple rainwater pump, that often means one of these arrangements:
Pump above the tank water level:
Tank → screened foot valve → suction pipe → pump
Pump with flooded suction:
Tank outlet → pump → check valve if required by the pressure system
Pressure system:
Tank → pump → required non-return valve → pressure tank and plumbing
The exact arrangement should follow the pump manufacturer's instructions.
Frequently Asked Questions
Can a water pump work without a check valve?
Yes. Some systems can operate without an external check valve, especially if the pump has one built in or if reverse flow is not a problem. Many pressure and suction-lift systems still require one somewhere in the system.
Where should a check valve be installed on a water pump?
It depends on the pump. A surface pump lifting water may use a foot valve at the bottom of the suction pipe. A pressure system may use a check valve after the pump. Some pumps already contain one internally.
Does a check valve go before or after a pump?
It can go on either side depending on its purpose. Before the pump, it can help maintain prime. After the pump, it can prevent pressurized water from flowing backward. Follow the pump manufacturer's plumbing instructions.
Is a foot valve the same as a check valve?
A foot valve is a type of check valve designed for the end of a suction pipe. It usually includes a screen that helps keep larger debris from entering the pipe.
Can a bad check valve make a pump cycle?
Yes. If water leaks backward through the valve, system pressure may fall after the pump shuts off. A pressure-controlled pump may then restart even when no fixture is being used.
Does a rain barrel pump need a check valve?
Not always. A pump fed from the bottom outlet of a rain barrel may stay flooded by gravity. A pump located above the water level is more likely to need a valve that keeps its suction line full.
Can a check valve reduce pump flow?
Yes. Every valve creates some resistance. An undersized, clogged, or unsuitable check valve can reduce flow, especially on the suction side of a pump.
