Plumbing Pipe Buying Guide | Plumbing Pipe Types Explained

Q: What type of pipes are used in plumbing?

Lots of different types are used in plumbing, but plastic (polybutylene, cross linked polyethylene and medium density polyethylene) and copper pipes are the most common. Pipes are separated into waste pipes and supply pipes, and the type you choose depends on where they’re used.

Q: What metal is used for pipes for plumbing in houses?

Copper is the metal used for pipes and plumbing in houses, but plastic is also very commonly used.

Q: Why is copper used for plumbing?

Copper pipes have a number of advantages that make them ideal for plumbing, mainly that they’re highly durable, impermeable, and inhibit bacterial growth.

Q: Which plumbing pipe is best?

For internal plumbing, both copper and plastic pipes have their merits. Plastic pipe, both PB and PEX types, are flexible and durable – but are not UV stable so can deteriorate if used outside. Copper pipes are suitable for external and internal use, inhibit bacterial growth, and are both fire resistant and highly durable – but come with a slightly higher price tag.

Q: How do you hide exterior plumbing pipes?

Exterior plumbing pipes can be hidden in a number of ways – such as covering with plants, a bench or seating area, painting the pipes to help them blend in, or using decorative covers. Just ensure your pipes can be accessed in the event of an issue.

Q: What causes plumbing to make noise?

There are a number of reasons for noisy plumbing, including: loose fittings, copper pipes expanding with heat, high water pressure, trapped air, and blockages or sludge build up.

Q: How do you measure plumbing pipes?

Plumbing pipe size is given in diameter. To determine the size of a plumbing pipe, simply measure the length from one outer wall to the opposite outer wall. For most internal domestic plumbing, this will be 15mm or 22mm, while commercial pipe diameter tends to be 28mm. Soil pipes and underground drain pipes are often 110mm or 160mm, but there are larger options available for different environments.

Q: What size are plumbing pipes?

Plumbing pipe sizes in the UK vary depending on their use. Internal supply pipes in homes are either 22mm or 15mm in diameter, while commercial environments need 28mm pipes to cope with demand. Waste pipes are between 21.5mm and 50mm in diameter, while soil pipes which carry solid waste are usually 110mm. Some underground soil pipes are 160mm when the plumbing to multiple houses is connected, or in commercial environments.

Q: What size are central heating pipes?

In most modern homes, central heating pipes will be standard 15mm pipes. You'll also find 22mm or 28mm pipes connect the boiler to pumps and points where pipes are diverted in the system.

Plumbing Pipe Buying Guide

Renovating your home or workplace? Or simply need to replace some old plumbing pipes? It's important to know the different types of pipe available to you. Plumbing is an essential system that carries fluids through pipes, and choosing the right type of pipe is key to ensuring yours runs smoothly!

External pipes need to be strong enough to withstand increased pressure when underground, brightly coloured so they can be easily seen for maintenance and identification, and flexible enough to be easily installed.

Internal pipes need to be easy to identify so there are no mistakes made with waste and mains water (generally wider pipes are used for waste water and thinner pipes for clean water), discreet so they’re not unsightly, and flexible enough to be easily installed in wall cavities.

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Types of External Plumbing Pipe

External plumbing pipes are used to carry clean water into the property up to the stop valve, and take waste water away from the property.

MDPE Pipe

MDPE pipe, also known as medium density polyethylene pipe, is used externally for supplying water to a property, usually mains water, up to the stopcock of the building. This type of pipe is bright blue so it can be easily identified in the ground.

This pipe is great for long-term use to supply water to a property. It won't corrode or deteriorate underground, so there's a minimal chance that it'll need repairing or replacing. MDPE pipe is also stress-fracture-resistant, meaning it won’t break under pressure when underground.

MDPE pipe isn’t UV stable, meaning it must be run underground – this can make it more difficult to access if it ever does need repairing or replacing. This type of pipe cannot carry hot water, meaning its only use is as a mains supply pipe.

Advantages

Will not corrode or deteriorate underground
Stress fracture resistant

Things to Consider

Not UV stable
Cannot carry hot water

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Underground Pipe

Underground pipe carries greywater and blackwater to the sewers from soil pipes. They’re terracotta coloured so they can be easily spotted underground for maintenance. You’ll find 110mm and 160mm underground drainage pipes, with 110mm most commonly used for domestic properties, whilst 160mm are used for commercial properties where the water volume is greater.

These pipes have a push-fit design meaning there’s no welding or tightening needed to install them. Underground pipes are made of PVC with a smooth finish. This improves water flow and reduces debris, helping to keep the pipes working well.

Underground pipes are not UV stable, and are therefore only suitable for underground use.

Advantages

Push fit design – no welding or tightening needed to install
Smooth finish of PVC improves water flow and reduces debris

Things to Consider

Not UV stable – only suited for underground use

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Soil Pipe

Soil pipes are made from PVC and are used to take black water and grey water from your toilet and sinks to the sewer. They’re big enough to allow solid waste to pass, and are vented near the top of a building to reduce odours and keep harmful gases away from the property. Soil pipes come in a variety of colours, and the colour chosen will often depend on the colour of the guttering.

The simple push-fit design and sealing rings of soil pipes make them easy and quick to install. The PVC is a strong, lightweight material with high chemical and UV resistance, making it ideal for transporting waste and soiled water. This also means soil pipes don't need to be installed underground away from sunlight.

The main consideration with soil pipes is the issue of blockages. These will occur more regularly than other types of pipes because of the purpose of soil pipes – to transport solid and liquid waste to sewers. Additionally, soil pipes make up a complex system called a soil stack with different components that should be installed by a qualified professional, as mistakes could be harmful, costly and smelly!

Advantages

Push fit design makes them easy to install
UV resistant
High chemical resistance

Things to Consider

Blockages are more likely than other pipes
Soil stack systems need professional installation and maintenance

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Types of Internal Plumbing Pipe

Internal pipes carry clean water around your property to taps, showers and toilets.

Plastic Pipe

There are two types of plastic plumbing pipes: PB (also known as polybutylene pipes) and PEX pipes (also known as cross linked polyethylene pipes). Pipe sizes are the diameter of the pipe; 15mm or 22mm are popular for domestic plumbing, whilst 28mm is used for commercial environments.

PEX is often viewed as a sturdier alternative to PB pipe. However, PB is more flexible and easier-to-manipulate. Both are quick and easy to install heat-free, ideal for tight spaces and protecting homes from heat damage. They’re interchangeable with other systems, and won't corrode over time with proper use.

Internal plastic pipes are not as robust as copper alternatives. They also cannot be used outside due to the increased risk of freezing as well as potential UV damage – both could cause the pipe to deteriorate and start leaking. If you have any water supply pipes on show, you may find copper alternatives are also more aesthetically pleasing.

Advantages

Quick and easy installation
Do not corrode over time
Interchangeable with other systems

Things to Consider

Cannot be used outside
Plastic is less aesthetically pleasing when on show
Not as robust as copper pipes

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Copper Pipe

Copper plumbing pipes were the pipe of choice before plastic pipes were invented, and are still used now – both externally and internally, as they’re UV stable. 15mm and 22mm diameter copper piping is used in domestic plumbing, while 28mm is used in commercial environments.

Copper pipes are robust and fire resistant, and prevent bacterial growth within the plumbing system. They’re also easier to recycle than plastic pipes. Copper compression fittings can be used with plastic pipes as they’re a type of flame-free copper fitting, making them reasonably flexible.

Copper pipes can be more difficult to install and repair than plastic pipes – although this shouldn’t be a problem for experienced plumbers. You'll also find copper pipes can't withstand acidic water. These pipes also come with a slightly higher price tag. Standard copper fittings cannot be used with plastic pipes as heat is required to connect them – making them less flexible than plastic plumbing unless you use compression fittings.

Advantages

Fire and UV resistant & inhibits bacterial growth
Recyclable
Compression fittings can be used with plastic pipes

Things to Consider

Can be difficult to install and repair
Come with a higher price tag
Can’t withstand acidic water

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Key Plumbing Pipe Features

Size

Plumbing pipes are typically measured by their diameter. For instance, internal supply pipes in domestic properties are commonly 22mm or 15mm in diameter, while commercial plumbing often uses pipes with a diameter of 28mm. Larger pipes are needed for commercial environments due to the greater volume of water that will be flowing through them every day.

Additionally, soil pipes and underground pipes are much larger in diameter than supply pipes, as these will carry solid waste that would otherwise get clogged. Waste pipe sizes are usually 110mm in diameter.

Colour

Plumbing pipes are colour-coded to make it easy to identify their purpose and locate them underground. For example, blue MDPE pipe and terracotta underground pipe can be easily spotted. However, soil pipes are often chosen to match the guttering – commonly black, brown or white.

Internal fittings will be either white or grey. White fittings are demountable, which means they can be removed without damaging the pipe. Grey fittings are non-demountable – ideal in rented properties so tenants aren't tempted to fix a problem themselves.

WRAS Approval

WRAS approval is an accreditation recognised by all of the UK’s water suppliers. This accreditation states which products have been through rigorous testing by an independent laboratory to meet set standards and ensure they're safe for use.

WRAS approval protects the water supply from contamination by toxic chemicals, or creating environments in which bacteria can grow. It also ensures the taste, colour and odour of the water is not being negatively affected by the plumbing element – whether that’s a tap, fitting, or pipe.

British Standards

The British Standards Institute sets the base level that plumbing pipes and fittings must reach before they are used in domestic or commercial environments. The BSI kitemark ensures both the products and the water they're supplying are safe for use.

The BSI standards will also confirm the pipes and fittings can be used in the way they’re intended. For example, they ensure central heating pipes can carry hot water without posing a danger or damaging the rest of the system.