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The three common types of check valves used in water systems are swing check valves, spring-loaded check valves, and ball check valves. All three let water move in one direction while helping stop it from flowing backward.
For a rainwater harvesting system, the right type depends on where the valve is installed, how much pressure is available, whether debris may be present, and how much resistance the pump can handle.
What Does a Check Valve Do?
A check valve is a one-way valve. Water pressure opens it when water moves in the intended direction. If the flow stops or tries to reverse, the valve closes.
Check valves can help:
- Keep a pump line full between cycles.
- Reduce backward flow from irrigation piping.
- Prevent water from draining back toward a tank.
- Maintain pressure in some pumped systems.
- Keep water moving in the intended direction between tanks or treatment stages.
A check valve is not the same as a shutoff valve. You normally do not open and close it by hand.
1. Swing Check Valve
A swing check valve has a hinged flap, sometimes called a disc, inside the valve body.
Forward-moving water pushes the flap open. When the flow stops or reverses, gravity and backward pressure push the flap closed.
Where swing check valves work well
Swing check valves are common in larger water lines and systems where keeping flow resistance low is important.
They can be useful for:
- Cistern outlet piping.
- Large rainwater transfer lines.
- Some irrigation systems.
- Low-pressure gravity-fed systems, if the valve is designed for the available pressure.
One advantage is that the water has a fairly open path when the valve is fully open.
What to watch for
A swing valve needs enough forward flow to move the flap. The valve may also depend on its installation position to close correctly.
Debris can prevent the flap from sealing. Roof grit, leaves, insects, sediment, or tank debris should be kept out of the valve with suitable screening or prefiltration.
Some swing valves can also close quickly when flow changes, causing a pressure shock known as water hammer.
Always follow the valve manufacturer's allowed installation positions and flow-direction arrow.
2. Spring-Loaded Check Valve
A spring-loaded check valve uses a spring to hold a disc or poppet against a seat.
Forward pressure compresses the spring and opens the valve. When pressure falls, the spring pushes the valve closed.
These valves are also commonly called spring check valves or inline check valves.
Where spring check valves work well
They are often used in:
- Pump discharge lines.
- Pressure systems.
- Irrigation piping.
- Filtration systems.
- Compact plumbing installations.
Because a spring closes the valve, it does not rely as heavily on gravity as a basic swing valve. This can make installation more flexible, provided the manufacturer approves the orientation.
What to watch for
The spring creates resistance.
A spring-loaded valve requires a certain amount of pressure before it opens. This is often called cracking pressure. Cracking pressure is simply the pressure needed to start opening the valve.
That resistance matters in low-pressure rainwater systems. A valve that works well after a pump may perform poorly on a weak gravity-fed line.
The valve can also become stuck or fail to seal if sediment reaches its internal parts.
3. Ball Check Valve
A ball check valve uses a movable ball inside the valve body.
Forward water flow moves the ball away from its seat, allowing water through. Reverse flow pushes the ball back against the seat and closes the passage.
Where ball check valves work well
Ball check valves can work well where water may contain more suspended material than a very clean plumbing supply.
They are commonly found in:
- Pumping systems.
- Wastewater applications.
- Some irrigation systems.
- Water-transfer lines.
Their simple internal movement can make them useful in applications where a hinged flap or small spring mechanism might be more prone to fouling.
What to watch for
A ball check valve can create more flow restriction than another valve of the same nominal pipe size.
Orientation can also matter. Some designs depend partly on gravity, while others are made to work in different positions.
Check the manufacturer's instructions rather than assuming every ball check valve can be mounted the same way.
Swing vs. Spring vs. Ball Check Valves
| Type | How it closes | Common advantage | Main consideration |
|---|---|---|---|
| Swing | Hinged flap swings onto seat | Low flow resistance when fully open | Position and debris can affect closing |
| Spring-loaded | Spring pushes disc onto seat | Fast closing and compact design | Requires pressure to overcome spring |
| Ball | Ball moves onto valve seat | Simple internal mechanism | Can add flow resistance |
None is automatically the best choice for every rainwater system.
Which Check Valve Is Best for a Rainwater System?
Start with the purpose of the valve.
For a low-pressure gravity-fed line, low resistance may be especially important. A swing valve designed for low-pressure service may be more suitable than a strong spring-loaded valve.
For a pump discharge line, a spring-loaded check valve is often worth considering because it closes positively when the pump stops.
For a line that may carry some suspended debris, a suitable ball check valve may be useful, but keeping sediment out of the plumbing is still important.
Alongside comparing check valve options, assess how the decision supports the whole collection process.
The valve must also match the rest of the system.
Check:
- Pipe diameter.
- Connection type and thread standard.
- Maximum operating pressure.
- Allowed installation position.
- Required opening pressure.
- Expected flow rate.
- Water temperature.
- Valve material.
- Manufacturer's intended application.
The nominal size printed on a valve does not always tell you how restrictive its internal passage is.
Check Valve Size Matters
A check valve is normally selected to match the connected pipe, but pipe size alone should not make the decision.
An undersized or restrictive valve can reduce flow. This matters when supplying garden irrigation, transferring water between tanks, or feeding a pump.
A poorly chosen valve on a pump's intake side can be especially troublesome because pumps generally perform better when suction restrictions are kept low.
If you are sizing a pumped system, consider the entire flow path rather than looking at the check valve alone.
Check Valves and Rainwater Pumps
A pump system may use a check valve to stop water from draining backward after the pump shuts off.
Some pump arrangements use a foot valve, which is essentially a check valve installed near the submerged end of a suction pipe. It helps keep the suction line filled.
Do not automatically add several check valves because one seems useful. Multiple valves create additional resistance and more places where debris or mechanical failure can stop flow.
Follow the pump manufacturer's requirements, particularly for suction piping, priming, pressure tanks, and built-in check valves.
Common Check Valve Problems
A check valve can fail even when it is the correct type.
Common problems include:
Sediment in the valve
Small particles can become trapped between the valve and its sealing surface. The valve may then leak backward.
Keeping roof debris and tank sediment out of the plumbing helps reduce this problem.
Valve installed backward
Most check valves have an arrow showing the intended direction of water flow.
Installing the valve backward can block flow almost completely.
Not enough pressure
A spring-loaded valve may not open properly if the system cannot provide enough pressure.
This is especially important with rain barrels and other gravity-fed systems.
Valve sticking closed
Mineral buildup, sediment, corrosion, or damaged internal parts can keep the valve from opening.
Valve not closing completely
A worn seat, trapped debris, damaged spring, or damaged ball or flap can allow water to leak backward.
Check Valves Need Maintenance
Check valves are often hidden in plumbing, so they can be forgotten until flow or pressure changes.
Include accessible check valves in routine system inspections.
Look for signs such as:
- Water draining backward after the pump stops.
- A pump losing its prime.
- Frequent pump cycling.
- Reduced water flow.
- Unusual banging or clicking.
- Pressure dropping when no water is being used.
Before opening a valve or pump line, shut off electrical power where applicable and safely release water pressure. Pump and pressure-system work can involve electrical and stored-pressure hazards.
Frequently Asked Questions
What are the three common types of check valves?
Three common types are swing check valves, spring-loaded check valves, and ball check valves. Other designs also exist, so these are not the only check valve types used in plumbing.
What is the simplest type of check valve?
A swing check valve has a relatively simple design. It uses a hinged flap that opens with forward flow and closes when water tries to reverse.
Is a spring check valve good for a rain barrel?
It depends on the available pressure. A rain barrel produces relatively low pressure, so a spring-loaded valve may create too much resistance if its required opening pressure is too high.
Can I install a check valve vertically?
Some check valves can be installed vertically, while others have orientation limits. Follow the manufacturer's installation instructions because the internal mechanism may depend on gravity or a specific flow direction.
Does a check valve reduce water flow?
Yes, every check valve creates some resistance. Spring strength, internal passage size, valve design, flow rate, and pipe size determine how noticeable the loss will be.
What is the difference between a check valve and a foot valve?
A foot valve is a type of check valve normally installed at the lower end of a pump suction line. Many foot valves also include a screen to help keep larger debris out of the suction pipe.
Can sediment damage a check valve?
Yes. Sediment can wear moving parts or become trapped against the valve seat, preventing the valve from closing completely. Prefiltration and regular tank maintenance can reduce the amount of debris reaching the valve.
