MDPE Pipes: Water Pipes & Gas Pipes

MDPE pipes for water and gas mains pipework available from stock in sizes 20-90mm we also keep compression fittings for all types of connections. All MDPE systems are approved for use within the UK and are WRAS approved.

Information and guides on MDPE pipe products

Here at EasyMerchant, we carry a huge range of MDPE pipe (medium density polyethylene) products - both for potable water applications, non potable water supply pipe jobs, and gas - and our great prices make all our products ideal, whether you're on a home DIY project or major site work.

Since we often get questions around the use and repair of MDPE pipe, we've answered some common queries here - and provided a couple of handy guides that'll help you decide which type is right for you - and how to tackle any problems you might face with existing installations.

Got a question you can't find an answer to? No problem - we've got a customer service team just an email, instant message, or phone call away!

More about these products

MDPE is short for Medium Density Polyethylene (sometimes known as Alkathene) - a type of thermoplastic that's favoured in the plumbing industry. It's sometimes referred to as poly-pipe - and, in drinking water (potable water) applications it's sometimes called 'barrier MDPE pipe'. 

This kind of polyethylene has a density of between 0.926-0.940 - making it less dense than HDPE - another commonly used polymer that features in building applications. While HDPE and some types of PVC can be sensitive to irregularities (notches) when it is in situ (possibility leading to stress cracking), true MDPE is more resilient to damage or corrosion - giving it a rating value that is perfect for underground water feeds where copper would have once been used.

Different colour - different use

Here, we'll take a detailed look at the different colours of products available - and what that means for their intended use:


what is the difference between blue and black MDPE water pipe?

Blue MDPE is used for below ground drinking water (potable water) supplies under BS EN 12201

Generally, this type comes in coils in sizes ranging from 25m to 150m - and ranges in width from 20mm to 180mm. All the sizes we carry are WRAS approved for use in the UK - each with the appropriate rating value.

Blue poly is inert - meaning it's chemically inactive - as a result, it's resistant to contamination from chemicals (both naturally occurring and man-made) and doesn't harbour the growth of any microbiological life - like bacteria, algae, or fungi.

Blue poly does not contain any chemical agent designed to resist the fading that occurs when the pipe is exposed to UV light (sunlight) - therefore, blue products designed exclusively for underground installation or installation where it is entirely shielded from light.


90mm Black PE100 SDR17 HPPE Water Mains Pipe x6m

Like blue poly, lengths of black MDPE are used to carry water - but strictly non-drinking water - otherwise known as non-potable water. 

So for instance, where blue poly would run from the mains water supply to a house, black MDPE would be used for the installation of water features, irrigation, industrial systems, or waste applications.


Yellow gas mains MDPE

Although yellow poly products are made of the same or similar material to other colours - it's actually used exclusively for gas installations and should never be used to carry water.

We carry a wide range of pipework and fittings here at EasyMerchant - including diameters of 25mm, 32mm, and 63mm.

Water Pipe Size Chart:

MDPE Pipe Size (mm)Avgerage Bore inside diameter (mm)Avgerage wall thickness (mm)Approximate weight per metre (kg)

Repairing MDPE pipes

We often have people get in touch with us to find out how to fix a leaking water supply underground.

Since the leak is underground - there's a fair amount of work involved getting to the problem, but when you've accessed it, carrying out the actual repair is reasonably straightforward. 

Finding the leak

If you're aware that there's a leak but you're not sure where it is, you can spend a lot of time digging and hoping for the best. What many people forget is that buildings insurance often covers 'trace and access' when you're dealing with leaking water - so check your policy carefully before you get the shovel out.

If you are covered for trace and access, a specialist leak detection firm will come and use thermal imaging equipment to track down the problem.

Repairing the issue

When you've got to the source of the problem, you'll need to carefully measure your water feed to make sure you're ordering the right size fittings for your repair. In the UK, the most common sizes are 20mm and 25mm - but if you find a size that's non-standard, don't panic, we'll be able to source exactly what you need - even if it's not on the shelf.

Making the cut

If you find you're working with a length that's cracked, you'll need to cut it out as neatly as possible. It goes without saying that you should make sure the water is turned of before making any cuts.

You can use a hacksaw for this job - but you might find you get a quicker and neater cut using a dedicated plastic pipe-cutter. With the cut made, you should remove any burrs that are left with a fairly fine file.

Installing or replacing fittings

You might open your pipework up and find that a fitting has failed. If this is the case, you can explore our range of fittings/accessories and find the replacement part and swap like-for-like. 

If it is a pipework issue you're dealing with, you'll need to attach a new section using a coupler. You'll need to use inserts to make sure there isn't too much pressure put on the MDPE by the compression fitting - but these are very cost-effective so will add no more than a couple of pounds to the job. 

With the coupler and any new length in place, you'll be able to turn the water supply on again. It's a good idea to leave your access point open until you're absolutely confident that the problem is resolved.

Need any help with parts for the job? Just get in touch with our customer service team!