Gas Pipe Upgrade Explained Re April 29, 2021

Gas Pipe Upgrade Explained

Engineer repairing a boiler

When we think about buying a new or replacement boiler, we often forget about the other elements that are needed, like the gas pipework. It’s even worse when we get told by our engineer that we need to upgrade our pipework before your boiler is even installed.

Without gas pipework, your boiler becomes an ugly ornament. Many boilers need to be supplied with a certain gas pipe size for them to comply with building regulations. For example; most gas combi boilers require a standard 22mm supply pipe, which will connect the boiler to the gas meter. However, the gas pipe size may need to be upgraded to a 28mm or 35mm in sections depending on bends and turns in the route from the boiler to the meter. If you have any concerns about how safe your current boiler is, we have a blog that covers boiler safety. 

Upgrading is also recommended if you are installing a larger output boiler as more gas is required. For example, if your existing boiler is a 24kW combi and you are installing a 30kW in its place, your gas pipework should also be upgraded due to higher hot water output. 

If you install a combi boiler and the gas pipe is not the required specification, you will be contravening Gas Safe regulations and the manufacturer’s instructions; the boiler will never perform to its full potential and you’ll be breaking the law.

It is known that a lot of older, open vented boilers and system boilers were fitted with 15mm gas pipes. This was because all they needed was to heat the water via the hot water cylinder within an hour or so. For those who would like to understand more about vented and unvented systems (why wouldn’t you?), we have a blog on this as well.

A gas pipe upgrade may not always be needed, depending on your existing pipework. If you are replacing a combi boiler with another combi boiler and your pipe is already 22mm from the meter to the boiler, it will be unlikely to need an upgrade. When you order a boiler from WarmZilla any gas pipework upgrades that may be required are included as standard.

However, issues can arise meaning that it will need to be. One of these issues could be that your pipework is not providing adequate pressure at the boiler, this could be due to carbon deposits in the pipework. It may look like nothing’s wrong, however, this can cause problems for your boiler and heating system in the future.

As the colder months come around, we all start cranking up the heating to keep us nice and warm. However, if your gas pipes are not the correct size, or need upgrading, this could not only make your heating system less efficient but could also put you and other members of the household in danger. 

If you think your gas pipework requires an upgrade, or if your Gas Safe heating engineer has mentioned to you that you will need to upgrade your pipework to have your new boiler fitted, you might be a little confused.

This next section is going to discuss everything you need to know about gas pipework, from how to check it, different piping materials, the cost to upgrade your pipework, and problems that may arise.

What is gas pipework?

When speaking to your Gas Safe heating engineer, they might have mentioned building or branch lines when discussing your gas pipework. Any idea what these are? Don’t stress, we’ve got your back. 

The piping inside your home is often referred to as the gas supply line or a building line. 

Branch lines are the pipework that runs to your appliances. Your branch line ends in a drop line, which is a vertical pipe that drops down to the appliance. You may hear your engineer refer to the drop line as a riser if it carries gas up to an appliance.

Which gas pipes are affected?

To ensure that all gas appliances fitted can operate at their highest output with the correct gas pressure, the appliances must be gas-rated by your Gas Safe heating engineer. Your heating engineer will test each appliance, such as your new boiler, fire or cooker, if the pressure required can not be achieved with your existing pipework, they will need to be upgraded.

How to know if I need to upgrade my pipework

Over time, pipes suffer from the elements, resulting in corrosion, rust, and eventual disrepair, which can directly affect the efficiency of your heating system or appliances.

Unless your home is under 5 years old, there may be a high chance that your gas pipework may need upgrading. But what are the signs to look out for to know if it needs upgrading for sure?

  • Strange smells – If your house has a strange stench, it could be the cause of a leaking gas line.
  • Hissing sounds – If there are hissing noises coming from your walls, there may be gas lines that are faulty or leaking and should be checked as soon as possible.
  • Line repair – As old lines can corrode over time, it is essential to replace them if they are old.
  • Corrosion – Gas lines can corrode at joints in the lines. This can cause leaks over time.
  • Deteriorating plant growth – If there are gas lines outside your home underneath the ground and the grass above it does not want to grow can indicate a leak in the line.
  • Building – If you build new items on your property, you need to make sure that you do not damage any of the lines.

The cost of upgrading your gas pipework

The price of upgrading your gas pipework can vary depending on the complexity involved whilst replacing the pipework. Other factors such as the current set-up of pipework and circumstances can also affect the price. 

When purchasing a new boiler with WarmZilla, you won’t have to worry about paying additional costs for a pipework upgrade as this is included in the price. 

When looking for a price to upgrade your gas pipework, it is always best to get multiple quotes from Gas Safe engineers to ensure that you are getting the best price. 

As mentioned, the more complex the upgrade, the more expensive it is likely to be. For example, if you live in a bungalow that has space under the floor, it will be more simple and cost-effective to upgrade than if you had to lift the floorboards. 

On average, upgrading your gas pipework can cost between £50 and £800. It is also important to note that the price of copper can fluctuate, which could affect the overall price.
The price of a gas pipe upgrade is included in the price when purchasing a new or replacement boiler with WarmZilla. 

Gas piping materials

The most common material used for gas piping is black steel. Galvanized steel, copper, brass or CSST (Corrugated Stainless Steel Tubing) can also be used in some areas. However, some utilities specifically prohibit the use of copper. 

In other areas, the use of copper is widespread. You should know what is acceptable in your area. Steel piping typically is black with malleable iron or steel fittings. Galvanized steel is used in some areas as well.


Have you heard your Gas Safe heating engineer talk about flex connectors? 

Flexible connectors are needed to connect appliances to the gas piping. It is essential to have a shut-off valve at the connection point of the rigid piping, this is kept in the same room as the appliance it is connected to. The flexible connectors can’t go through walls, floors or ceilings, nor can they be concealed. 

Thread seal tape

Thread seal tape (often mistakenly referred to as Teflon® tape) that is white is not recommended as a joining compound for steel gas piping. This is because cutting oils that remain on the pipe threads from the manufacture may prevent the tape from sealing.

In some areas, yellow thread seal tape is allowed however, pipe dope sealant is preferred and may be all that is allowed. If you are unsure, you may want to check with the gas utility and ask whether you should report as a defect any piping installations with thread seal tape of any colour.

Bonding gas piping

Most authorities do not allow the use of gas piping as a grounding means for the electrical service.

Bonding the gas piping to the electrical grounding system is a requirement, however, in many jurisdictions. Often, this is done by attaching the gas piping to the supply water piping (assuming it is grounded) frequently near the water heater. To prevent an electrical potential buildup within the gas piping that could lead to arcing, which might ignite the gas, we want to keep the gas piping at zero electrical potential by bonding it to the grounding system.

Problems that may arise as a result of gas piping

The following problems are typical on gas piping:

  • Leaks
  • Inappropriate materials
  • Inadequate support
  • Rusting
  • No drip leg
  • Missing shut-off valve
  • Improper connections
  • Plastic pipe exposed above grade
  • Piping in chimneys or duct systems
  • Copper tubing not properly labelled

The implications of all of these problems are possible gas leaks and explosions.

This blog has discussed some of the basics of gas piping which has hopefully helped you to understand your gas pipework a little more in order to identify when your gas pipework may need upgrading, as well as potentially unsafe situations. If you are unsure about anything regarding your gas pipework, we recommend contacting your local heating engineer.

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