Product Description

Keyplumb 20mm MDPE Coupling – WRAS Approved PN16

Model: K51091

The Keyplumb 20mm MDPE Coupling joins two compatible lengths of 20mm MDPE water pipe. Therefore, it provides a simple way to extend a pipe run or repair a damaged section.

The compression fitting uses an acetal thermoplastic grip ring and a rubber O-ring to create a strong, watertight joint. In addition, the twist-compression design allows quick installation without specialist tools.

This 20mm MDPE pipe connector suits domestic and commercial cold-water systems. Furthermore, its WRAS approval allows use with suitable potable-water applications.

20mm MDPE Coupling at a Glance

• Product: Equal MDPE pipe coupling
• Brand: Keyplumb
• Model: K51091
• Connection size: 20mm x 20mm
• Joint type: Twist-compression
• Pressure rating: PN16 at 20°C
• Maximum stated water temperature: 23°C
• Water suitability: Cold-water services
• Potable-water use: WRAS approved
• Grip ring: Acetal thermoplastic
• Seal: Rubber O-ring
• Pipe liners: Required in both pipe ends
• Application: Domestic and commercial water systems

Key Features and Benefits

• Joins two 20mm MDPE pipes of the same size
• Creates a secure compression connection
• Uses a tough acetal grip ring
• Includes a rubber O-ring for a watertight seal
• Offers a PN16 pressure rating at 20°C
• Supports suitable potable-water applications
• Holds WRAS approval
• Requires no heat, solder or solvent cement
• Needs no specialist jointing tools
• Allows straightforward installation
• Suits underground cold-water services
• Works in domestic and commercial systems
• Offers a strong and durable connection
• Allows future removal where the installation permits access

What Is a 20mm MDPE Coupling?

A 20mm MDPE coupling connects two separate lengths of 20mm MDPE pipe. Both sides of the fitting accept the same pipe size. Therefore, installers also call it an equal coupling or straight MDPE connector.

The coupling fits between the two pipe ends and creates a straight connection. As a result, it can extend a new pipe run or reconnect an existing water service.

For example, you may use the coupling when:

• Joining two coils of 20mm MDPE pipe
• Extending an existing cold-water service
• Repairing a damaged pipe section
• Replacing a leaking or damaged fitting
• Connecting new pipe to compatible existing MDPE pipe

However, use the coupling only with compatible 20mm MDPE pipe. Other pipe materials and sizes may need a specialist adaptor.

How Does the Compression Joint Work?

Each side of the coupling contains a compression nut, grip ring and O-ring seal. Together, these parts hold and seal the MDPE pipe.

First, the grip ring holds the outside of the pipe and prevents it from pulling out. Meanwhile, the rubber O-ring seals around the pipe surface.

Next, tightening the compression nut brings the parts together. As a result, the fitting forms a strong mechanical joint without heat, solder or solvent adhesive.

The connection also allows quick assembly on site. Therefore, installers can use the fitting in locations where hot-work methods would prove difficult or unsuitable.

Always Use 20mm Pipe Liners

Always insert a suitable 20mm pipe liner into each MDPE pipe end before making the joint.

MDPE pipe can compress under pressure from the fitting. However, the liner supports the pipe from the inside and helps it keep the correct shape.

Therefore, pipe liners help the grip ring and O-ring work correctly. They also reduce the risk of:

• Pipe distortion
• Poor grip
• Leaks around the O-ring
• Movement under water pressure
• Joint failure

The coupling does not replace the need for pipe liners. As a result, you will normally need two suitable 20mm liners for one complete joint.

Suitable Applications

The Keyplumb 20mm MDPE Coupling suits a wide range of domestic and commercial cold-water installations.

For example, installers may use it for:

• Underground mains-water services
• Domestic incoming water supplies
• Commercial cold-water pipework
• Garden and outdoor water supplies
• Outbuilding water connections
• Agricultural cold-water services
• Replacement MDPE pipe sections
• New 20mm MDPE pipe runs

However, always confirm that the pipe, fitting and complete system suit the intended water quality, pressure and temperature.

WRAS Approved for Potable Water

The coupling holds WRAS approval for suitable potable-water applications. Therefore, it can form part of a drinking-water installation when the installer follows the approval conditions and current Water Fittings Regulations.

WRAS approval helps show that the product meets the relevant requirements for contact with wholesome water. However, the installer must also use compatible approved pipe, liners and other fittings.

In addition, keep every component clean during storage and installation. Dirt inside the fitting or pipe may affect water quality and damage the O-ring.

PN16 Pressure Rating

The coupling carries a PN16 pressure rating at 20°C. PN16 indicates a nominal pressure rating of 16 bar under the stated test or reference conditions.

However, the safe working pressure of the complete system depends on several factors. These include:

• Water temperature
• Pipe pressure rating
• Installation quality
• Joint condition
• Water-hammer risk
• Local regulations
• Manufacturer guidance

Therefore, never judge the complete system by the fitting rating alone. Instead, use the lowest rating that applies to any pipe, valve or fitting in the installation.

Suitable Water Temperature

This coupling suits cold-water systems with water temperatures up to the stated 23°C limit.

Therefore, do not use it for hot-water or central-heating pipework. Higher temperatures can affect the pipe, seals and pressure rating.

For hot-water services, choose a pipe and fitting system that the manufacturer specifically approves for the required temperature and pressure.

How to Fit a 20mm MDPE Coupling

Always follow the latest Keyplumb instructions. However, the following steps provide a general installation guide:

1. Turn off the water: First, isolate the supply and drain the relevant pipe section.
2. Cut the pipe square: Next, use a suitable pipe cutter to create a clean, straight end.
3. Remove damage: Cut away deep scratches, distortion or damaged pipe.
4. Clean the pipe: Remove soil, grit, moisture and other dirt from the pipe end.
5. Check the fitting: Make sure the nut, grip ring and O-ring sit correctly.
6. Fit the pipe liner: Push a suitable 20mm liner fully into each pipe end.
7. Insert the pipe: Push the pipe into the coupling until it reaches the internal stop.
8. Tighten the nut: Then, tighten the compression nut in line with the manufacturer’s instructions.
9. Repeat the process: Connect the second pipe to the other side.
10. Test the joint: Finally, restore the water slowly and check carefully for leaks.

Do not overtighten the nuts because excess force may damage the fitting. Likewise, do not use unapproved oils, grease or sealants on the O-ring.

Preparing the MDPE Pipe

Good pipe preparation helps create a reliable connection. Therefore, inspect both pipe ends before assembly.

First, make sure each cut sits square to the pipe. An angled cut may stop the pipe from reaching the internal stop.

Next, check the outside surface. Deep scratches may pass under the O-ring and create a leak path. Therefore, remove any badly marked section before fitting the coupling.

Finally, clean away grit and soil. Small particles can damage the seal or stop the pipe from entering fully.

Can You Reuse the Coupling?

The compression design allows dismantling in many accessible installations. However, inspect every internal part before reuse.

Replace damaged, worn or distorted grip rings and O-rings. In addition, replace the complete fitting if the body or compression nut shows cracks, impact damage or heavy wear.

Never reuse a damaged pipe liner. Instead, fit a new liner that matches the pipe size and specification.

Underground Installation Guidance

Follow current regulations and local water-supplier requirements when installing MDPE pipe underground.

First, protect the pipe and fitting from sharp stones and building waste. Next, provide the correct trench depth and bedding material for the installation.

In addition, avoid unnecessary underground joints where possible. A continuous pipe length can reduce future leak points.

If you install the coupling underground, record its location before backfilling. This information can make future maintenance easier.

Finally, pressure-test the connection before covering it. Do not bury a joint until you have checked it for leaks.

Common Installation Mistakes to Avoid

• Forgetting to install pipe liners
• Using the wrong liner size
• Cutting the pipe at an angle
• Inserting dirty or damaged pipe
• Failing to push the pipe fully home
• Overtightening the compression nuts
• Using the coupling on hot-water pipework
• Connecting an unsuitable pipe material
• Burying the joint before leak testing
• Using damaged grip rings or O-rings

Careful preparation takes only a short time. However, it can greatly reduce the risk of leaks and future repairs.

Why Buy from SNH Tradecentre?

• Competitive prices: We offer excellent value across our MDPE pipe and fitting range.
• Matching components: Choose from MDPE pipe, liners, elbows, tees, valves and adaptors.
• Helpful advice: Our team can help you identify compatible pipe and fittings.
• Local collection: Collect eligible stock from our Birchington trade counter.
• UK delivery: Select from the available delivery options at checkout.
• Trade and public welcome: We supply plumbers, builders, contractors and homeowners.
• Established merchant: Buy from an experienced plumbing and heating supplier.

Need help choosing the correct MDPE fitting or pipe liner? Call SNH Tradecentre on 01843 842727. If possible, have the pipe size, pipe colour and required connection type ready.

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Frequently Asked Questions

What does a 20mm MDPE coupling do?

It joins two lengths of 20mm MDPE pipe in a straight line. Therefore, you can use it to extend or repair a compatible cold-water pipe.

What size are the coupling connections?

Both ends accept compatible 20mm MDPE pipe. As a result, this product forms an equal 20mm x 20mm connection.

Can I use it with blue MDPE pipe?

Yes, it suits compatible 20mm blue MDPE water pipe. However, always check the pipe specification before installation.

Can I use it with black MDPE pipe?

It may suit compatible 20mm black MDPE pipe. However, confirm the pipe size, pressure rating and intended water use first.

Do I need pipe liners?

Yes. Insert a suitable 20mm pipe liner into each pipe end. Therefore, one coupling will normally need two liners.

Why do MDPE pipes need liners?

The liners support the pipe from the inside. As a result, they help the grip ring hold firmly and allow the O-ring to create a reliable seal.

Do I need specialist tools?

No specialist jointing tools are normally required. However, you will need a suitable pipe cutter and the tools recommended by the fitting manufacturer.

Does the coupling need solvent cement?

No. The grip ring, O-ring and compression nut create the joint. Therefore, do not use solvent cement.

Can I use PTFE tape on the joint?

The MDPE pipe connections do not normally need PTFE tape. The internal O-ring creates the seal. Therefore, follow the manufacturer’s instructions and avoid unapproved sealing products.

Is the coupling suitable for drinking water?

Yes, the product holds WRAS approval for suitable potable-water applications. However, the complete installation must also meet current Water Fittings Regulations.

What does PN16 mean?

PN16 indicates a nominal pressure rating of 16 bar at the stated reference temperature. However, the lowest-rated part will limit the complete system.

Can I use this coupling for hot water?

No. This fitting suits cold-water applications with a stated maximum water temperature of 23°C. Instead, use an approved hot-water system for higher temperatures.

Can I install the coupling underground?

Yes, it can form part of a suitable underground MDPE water system. However, follow current regulations, protect the joint and test it before backfilling.

Can I reuse the coupling?

You may reuse it if every part remains clean and undamaged. However, replace worn grip rings, seals, liners or damaged fitting bodies.

Can I join 20mm MDPE to 25mm MDPE with this coupling?

No. This equal coupling has two 20mm connections. Instead, use a suitable 25mm x 20mm reducing coupling.

Can I connect MDPE directly to copper pipe?

Not with this equal coupling. Instead, use a suitable MDPE-to-copper transition fitting that matches both pipe sizes.

Who can install an MDPE coupling?

A competent installer should complete the work. In addition, the installation must follow current Water Fittings Regulations and local water-supplier requirements.

Manufacturers can update specifications and approval details. Therefore, check the latest Keyplumb product information before installation.