15mm 逆止弁の完全ガイド: 知っておくべきことすべて

2025-09-07

Updated on 2025-09-15
William Leo
Directional Valve

If you've ever wondered how to prevent water from flowing backward in your pipes, you need a non-return valve (also called a check valve or one-way valve). Today, we'll focus on 15mm non-return valves – one of the most popular sizes for home and small business use.

What is a 15mm Non-Return Valve?

A 15mm non-return valve is a small but mighty device that allows water or other fluids to flow in only one direction. Think of it like a door that only swings one way – when water tries to flow backward, the valve automatically closes to stop it.

		
			Why the 15mm size matters:
		
				Perfect for standard home plumbing (fits 1/2 inch pipes)
			
				Handles up to 36 liters per minute
			
				Compact enough for tight spaces
			
				Most common size for residential use

Key Benefits

Prevents backflow – Stops contaminated water from mixing with clean water

Protects equipment – Keeps pumps and water heaters safe from reverse flow

Saves money – Prevents costly system damage

Easy to install – Simple DIY project for most homeowners

How Does a Non-Return Valve Work?

The science behind these valves is surprisingly simple:

When water flows forward: The valve opens automatically due to water pressure

When water tries to flow backward: The valve closes tight, creating a seal

No power needed: Works purely on water pressure and gravity

Most 15mm valves open when water pressure reaches just 0.1 to 0.15 bar – that's very little pressure, about the same as water flowing from a height of 3 feet.

Types of 15mm Non-Return Valves

Not all non-return valves are created equal. Here are the main types you'll find:

1. Swing Check Valves

How they work: A hinged flap swings open and closed

Best for: Basic home plumbing, low-pressure systems

Pros: Cheap, simple, easy to install

Cons: Slower response time

Price range: $8-20

2. Spring Check Valves

How they work: A spring pushes a disc to open and close

Best for: Pump outlets, systems with changing pressure

Pros: Fast response, reliable, adjustable opening pressure

Cons: Spring can wear out over time

Price range: $12-25

3. Ball Check Valves

How they work: A ball rolls to block or allow flow

Best for: Washing machines, hot water systems

Pros: Easy to maintain, very reliable seal

Cons: Needs minimum water pressure to work

Price range: $10-22

4. Dual Plate Valves

How they work: Two plates flip open like butterfly wings

Best for: High-flow applications, tight spaces

Pros: Lowest pressure loss, very fast action

Cons: More expensive

Price range: $15-35

Technical Specifications You Should Know

When shopping for a 15mm non-return valve, here are the key specs to look for:

Specification	Typical Range	What It Means
Maximum Pressure	12-25 bar	How much pressure the valve can handle
Flow Rate	Up to 36 L/min	How much water can pass through
Temperature Range	-20°C to +110°C	Safe operating temperatures
Opening Pressure	1.7-2.1 kPa	Minimum pressure needed to open
Connection Type	BSP threads	How it connects to your pipes

Material Options

Brass (Most Popular)

Great for drinking water
Resists corrosion
Affordable ($8-20)
Perfect for home use

Stainless Steel

Industrial strength
Handles high temperatures
More expensive ($15-35)
Best for commercial use

Plastic (PVC/PP)

Lightweight and cheap ($5-12)
Good for chemical applications
Lower pressure rating
Not suitable for hot water

Where to Use 15mm Non-Return Valves

Home Applications

Hot water systems – Prevents cold water from backing into hot water lines
Washing machines – Stops dirty water from contaminating clean water supply
Garden irrigation – Prevents soil contamination of drinking water
Water pumps – Protects pump from damage

Commercial Uses

Building water systems – Prevents cross-contamination
Industrial processes – Controls flow direction in manufacturing
Fire protection systems – Maintains water pressure in emergency systems

Installation Guide: Step by Step

Tools You'll Need:

Adjustable wrench
PTFE tape (thread sealant)
Pipe cutter (if needed)

Installation Steps:

Turn off water supply – Always start with water off!

Choose the right location – Install as close as possible to the equipment you're protecting

Check flow direction – Look for the arrow on the valve body – this shows which way water should flow

Prepare the pipes – Clean threads and apply PTFE tape

Install the valve – Hand-tighten first, then use wrench to secure (don't over-tighten!)

Test the system – Turn water back on slowly and check for leaks

Install horizontally when possible for best performance
Leave space around the valve for future maintenance
Consider a union-type valve for easier removal later

Maintenance and Troubleshooting

Regular Maintenance (Every 6-12 Months)

Check for leaks around the valve
Test that water flows freely in the correct direction
Listen for unusual noises that might indicate problems

Common Problems and Solutions

Problem: Valve won't open

Solution: Check for debris blocking the mechanism. Clean or replace if necessary.

Problem: Water leaking around the valve

Solution: Tighten connections or replace worn seals.

Problem: Valve chattering or making noise

Solution: Usually means the valve is too big for the flow rate. Consider a smaller valve or install a flow restrictor.

Problem: Valve sticking in open position

Solution: Debris or mineral buildup. Remove and clean the valve internals.

Top Brands and Where to Buy

Recommended Brands

Watts APEX

(Premium Choice)

Excellent build quality
WRAS certified for drinking water
Price: $12-18
Available at: Professional plumbing suppliers

Flomasta

(Best Value)

WRAS approved
Easy to find in stores
Price: $8-15
Available at: B&Q, major home improvement stores

RS PRO

(Industrial Grade)

Heavy-duty construction
Long warranty
Price: $15-25
Available at: RS Online, industrial suppliers

Brymec

(Reliable Middle Ground)

Good balance of price and quality
WRAS certified
Price: $10-18
Available at: Online plumbing retailers

Where to Shop

Home improvement stores: B&Q, Home Depot, Lowe's
Online retailers: Amazon, specialized plumbing sites
Trade suppliers: For professional-grade valves
Local plumbing stores: Often have expert advice

Buying Tips: What to Look For

Essential Features

Certification marks – Look for WRAS, NSF, or other water safety approvals

Pressure rating – Make sure it exceeds your system pressure

Temperature rating – Consider your hottest water temperature

Union connections – Makes future maintenance much easier

Red Flags to Avoid

No certification marks – Could be unsafe for drinking water

Unusually cheap prices – Quality issues likely

No flow direction arrow – Sign of poor manufacturing

Limited warranty – Manufacturer doesn't stand behind product

Cost Analysis: What Should You Expect to Pay?

Quality Level	Price Range	Best For	Expected Lifespan
Budget	$5-10	Basic applications, non-critical systems	2-5 years
Mid-range	$10-20	Home plumbing, most applications	5-8 years
Premium	$20-35	Commercial use, high-reliability needs	8-15 years

Money-saving tip: It's usually better to buy one good valve than to replace cheap ones multiple times.

Frequently Asked Questions

Q: Can I install a 15mm non-return valve myself?

A: Yes! It's a straightforward job for most DIYers. Just remember to turn off the water first and don't over-tighten.

Q: How do I know if my valve is working?

A: The easiest test is to disconnect the pipe downstream and see if water flows backward when you turn off the supply. No backflow = working valve.

Q: How long do non-return valves last?

A: With proper installation and maintenance, a good quality valve should last 5-10 years in typical home use.

Q: Do I need a plumber to install one?

A: Not usually, but if you're not comfortable working with plumbing or if the installation requires cutting into main supply lines, it's worth hiring a professional.

Q: Can I use a 15mm valve on a 1/2 inch pipe?

A: Yes! 15mm and 1/2 inch are essentially the same size in plumbing terms.

Conclusion: Making the Right Choice

Protect Your Plumbing Investment Today

A 15mm non-return valve is a small investment that can save you from big problems. Whether you're protecting your home's water supply, keeping your washing machine from contaminating your drinking water, or safeguarding expensive equipment, the right valve makes all the difference.

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