Plastic Non-Return Valves: A Complete Guide

When water flows through your pipes, sometimes it tries to go the wrong way. That's where plastic non-return valves come to the rescue! These simple but clever devices make sure liquids and gases flow in only one direction, protecting your equipment and keeping your systems running smoothly.

In this guide, we'll explore everything you need to know about plastic non-return valves (also called check valves). Whether you're a homeowner, engineer, or maintenance worker, you'll discover how these affordable flow controllers can solve your problems.

What Is a Non-Return Valve?

A non-return valve is like a one-way door for fluids. It opens when liquid or gas flows in the right direction, but slams shut when flow tries to reverse. Think of it as a traffic cop that only allows movement in one direction.

Other names you might hear:

Check valve
One-way valve
Backflow preventer
Stop valve

The "non-return" name tells you exactly what it does - it doesn't let fluid return or flow backward.

Why Choose Plastic Over Metal?

Plastic non-return valves have become incredibly popular, and here's why:

Cost Savings

Cheaper upfront: Plastic valves cost 50-70% less than metal ones
Lower installation costs: They're lightweight and easier to handle
Reduced maintenance: No rust or corrosion means fewer replacements

Superior Corrosion Resistance

Unlike metal valves that can rust, corrode, or pit over time, plastic valves laugh at harsh chemicals. They work great with:

Acids and bases
Chlorinated water
Salt water
Many industrial chemicals

Lightweight Champion

A plastic valve weighs about half as much as a similar metal valve. This makes installation easier and reduces stress on your pipes.

Smooth Interior

The inside walls of plastic valves are naturally smooth, which means:

Less pressure loss
Better flow rates
Reduced buildup of deposits

Types of Plastic Non-Return Valves

Not all non-return valves work the same way. Here are the main types and when to use each:

1. Swing Check Valves

How they work: A hinged disc swings open when flow pushes it, then swings closed when flow stops.

Best for:

High flow rates
Low pressure loss systems
Horizontal or upward vertical installation

Watch out: They can create water hammer (loud banging) if flow stops suddenly.

2. Ball Check Valves

How they work: A plastic ball sits in a cage. Flow pushes the ball up and away from the seat. When flow reverses, the ball drops back down to seal the opening.

Best for:

Dirty water with particles
Systems that start and stop often
Self-cleaning applications

Bonus: Great for slurry and wastewater because particles can't easily jam the ball.

3. Diaphragm Check Valves

How they work: A flexible rubber or plastic disc bends to let flow through, then springs back to seal against backflow.

Best for:

Bubble-tight sealing
Chemical applications
Any installation angle
High-purity systems

Why they're special: They provide the best sealing of all plastic check valve types.

4. Lift Check Valves

How they work: A piston or disc lifts straight up when flow starts, guided by a stem or cage.

Best for:

Quick shut-off
Preventing water hammer
Vertical installations

Trade-off: Higher pressure loss than swing types, but better sealing.

5. Foot Valves

How they work: Basically a check valve with a strainer screen attached to the bottom.

Best for:

Pump suction lines
Keeping pump primed
Preventing debris from entering pumps

Common use: Often seen in irrigation and water well systems.

Plastic Materials: Picking the Right One

The plastic material you choose makes all the difference. Here's a breakdown of the most common options:

PVC-U (Unplasticized PVC)

Temperature limit: Up to 140°F (60°C)
Pressure rating: 150-235 PSI
Best for: Water systems, light chemicals, irrigation
Cost: Most economical choice
Watch out: Not good with hot water or solvents

CPVC (Chlorinated PVC)

Temperature limit: Up to 200°F (93°C)
Pressure rating: 150-235 PSI
Best for: Hot water, chemical processing
Advantage: Handles heat better than regular PVC
Cost: More expensive than PVC but still affordable

PP (Polypropylene)

Temperature limit: Up to 180°F (82°C)
Pressure rating: Around 150 PSI
Best for: Food processing, high-purity applications, acids
Special feature: Very chemically inert and lightweight
Limitation: Can't handle strong oxidizers

PVDF (Polyvinylidene Fluoride)

Temperature limit: Up to 280°F (140°C)
Pressure rating: 150-230 PSI
Best for: Harsh chemicals, semiconductor manufacturing, high-temp applications
Premium choice: Excellent chemical resistance
Cost: Most expensive plastic option

Where Are Plastic Non-Return Valves Used?

These versatile valves pop up in countless applications:

Water Treatment Plants

Prevent contaminated water from flowing back into clean supplies
Protect expensive pumps and equipment
Handle chlorinated water that would corrode metal valves

Chemical Processing

Control corrosive chemicals that eat metal valves
Prevent dangerous chemical mixing
Maintain process purity

Agriculture & Irrigation

Keep irrigation lines from draining when pumps stop
Prevent fertilizer backflow into water sources
Handle dirty water with soil particles

Swimming Pools

Prevent pool water from flowing back through heaters
Keep chemicals from mixing inappropriately
Protect circulation equipment

Residential Plumbing

Stop sewage from backing up into homes
Prevent hot water heater backflow
Protect washing machines and dishwashers

Aquaculture (Fish Farming)

Control water circulation in fish tanks
Prevent system drainage during maintenance
Handle salt water that corrodes metal

Installation Tips for Success

Getting your plastic non-return valve installed correctly is crucial for long-term success:

Direction Matters

Always install with the arrow on the valve body pointing in the flow direction. Get this wrong and the valve won't work at all!

Key Installation Guidelines

Pipe Support

Even though plastic valves are lightweight, support the pipes on both sides. This prevents stress that could crack the valve over time.

Straight Pipe Runs

Install the valve with at least 5 pipe diameters of straight pipe upstream and 10 diameters downstream when possible. This ensures smooth, even flow.

Connection Methods

Solvent welding: Most common for PVC/CPVC. Clean joints thoroughly and use proper cement
Threaded: Use PTFE tape for leak-free connections
Flanged: Great for larger valves that might need future removal

Temperature Considerations

Remember that plastic gets weaker as temperature increases. A PVC valve rated for 235 PSI at room temperature might only handle 50 PSI at 140°F.

Common Problems and Solutions

Even the best valves can have issues. Here's how to troubleshoot:

Problem	Possible Causes	Solutions
Valve Won't Stop Backflow	Dirt on the valve seat Worn sealing surfaces Insufficient back pressure to close the valve	Remove and clean the valve Replace worn parts Consider a spring-loaded valve for low-pressure applications
Chattering or Vibration	Flow rate too low for valve size Turbulent flow from nearby fittings Valve oversized for the application	Use a smaller valve Ensure proper straight pipe runs Check system design
High Pressure Loss	Wrong valve type for application Valve too small Internal damage or obstruction	Switch to swing or ball type for lower pressure loss Size valve properly for flow rate Inspect and clean or replace valve

Maintenance Made Easy

Plastic non-return valves need much less maintenance than metal ones, but a little care goes a long way:

Regular Inspection (Every 3-6 Months)

Listen for unusual noises
Check for leaks around connections
Verify proper flow direction

Cleaning (As Needed)

Remove valve if it has union connections
Clean valve seat and moving parts
Rinse with appropriate solvent
Check seals and gaskets

Replacement Parts

O-rings and gaskets: Replace every 2-3 years
Diaphragms: Check annually for tears or stiffness
Springs: Rarely need replacement but check for corrosion

When to Replace

Cracking in valve body
Persistent leaking after cleaning
Loss of spring tension
Chemical attack damage

Cost Considerations: Plastic vs. Metal

Making the right choice involves looking at total costs over the valve's lifetime:

Cost Factor	Plastic Valves	Metal Valves (Stainless)
Initial Purchase Price	$15-150 for common sizes	$50-500 for similar sizes
Installation Costs	Lower due to light weight and easy handling	Higher due to weight and support requirements
Maintenance Costs (10 Years)	Near zero in corrosive service	Can exceed original valve cost
Energy Costs	Smooth bore reduces pumping costs	May have higher friction losses