13 August 2025
Repairing a pipeline doesn’t always require a total shutdown of the entire system, or closing of valves. Not only would it be costly to get it back up and running, but it could lead to further network issues, service interruptions for asset owners and customers. It could also lead to potential transient pressure effects or water quality issues.
For many situations, it’s much more efficient to temporarily isolate sections of a live pipeline instead.
At Hy-Ram, we understand the critical importance of keeping pipeline systems both operational and well-maintained. That’s why we manufacture and distribute specialist tools and equipment for line stopping – proven solutions for pipeline maintenance. They can reduce downtime by up to 40%, and allow work to be carried out safely and efficiently.
In this guide, we will cover everything you need to know about the line stopping procedure.
What is line stopping?
Line stopping (also known as flow stopping) is defined as a method of temporarily isolating a section of pipeline. This allows for maintenance, repairs, additions, inspections or general changes to be made to the pipeline.
First and foremost, line stopping is specially designed to prevent the shutdown of an entire pipeline system. This method significantly reduces disruption to customer supply, as well as saving costs for re-pressurising, re-testing and restoring the system. Line stopping is a far more cost-effective and practical solution and avoids the operation of mechanical network valves, which could affect a larger section of pipelines or be a significant distance away from the working area.
Flow stopping also keeps workers and operators safe while they carry out these essential repairs and upgrades. This method aims to ensure that there is little to no loss of fluids or gases, with most systems incorporating a bypass to alleviate pressure and maintain customer supply.
Line stopping is most commonly used in the water and gas sectors. The process can be utilised in many applications of infrastructure maintenance or enhancements, such as valve replacement, fire hydrant upgrades, air valve maintenance, district meter installation, PRV implementation, mains replacement programmes, network resilience works, developer services operations… and many more.
Line stopping methods
There are various methods to choose from when it comes to line stopping. Choosing the right one depends on the specific application, medium/matter (gas, water), pipe material, operating pressure and more.
Let’s break down each method:
Gas Bagging off
“Bagging off” is one of the most commonly used line stopping techniques, and originated in the gas sector due to increasing demand to expand or replace sections of gas networks, whilst maintaining supply with the highest levels of safety.
The WASK 312 Gas Bagging off equipment and WASK Teeset drilling and tapping machine in conjunction with the Sarco Resistra GIS/E4 350mbar high visibility yellow self-centring gas bag with BSI product quality Kitemark accreditation, are the most commonly used equipment to perform the operation.
They are used for low-pressure gas applications, typically on metallic pipelines such as Cast Iron, but sometimes on plastic pipe systems such as PE.
The equipment facilitates the insertion of four specialist gas bags into the hose main, with the use of an integral bypass system.
Once inside the pipe, the bag will then be expanded to form a tight seal against the pipe wall and stop the flow of gas.
There are dedicated equipment variants for both gas and water, with specific line/flow stopping bags for each.
This is a simple, cost-effective method that requires minimal equipment, making it a practical choice.
Squeezing off
A pipe squeeze-off tool is typically used with plastic pipes, primarily polyethylene (PE) for gas distribution networks, but has been used on clean/potable water mains successfully for many years.
Squeeze off is an excellent option for low cost and emergency response, due to the ease of applying the tool and speed of installation. You can view our PE pipe squeeze off tools here.
The process can involve setting up a bypass to ensure continuous flow to end users while the work is performed, depending on the project and pipe size. This normally involves fusing EF top tees or saddles to the pipe and connecting, once pressure tested correctly.
Next, a suitable squeeze off tool can be correctly applied to the PE pipe, and a manual or hydraulic feed then compresses it to temporarily stop flow. Squeeze off stops are manufactured to stringent tolerances, in Hy-Ram’s dedicated in-house CNC machining centre, to ensure that correct pipe wall compression is achieved.
Depending on the pipe size and SDR, Hy-Ram offers different tools with single applications or modular designs that can facilitate four simultaneous squeeze points.
View our PE pipe squeeze off range, approved to GIS/PL2-7 by Cadent Gas for use on PE80 and PE100 pipelines from 16mm to 630mm.
To resume the flow and allow the PE pipe to regain its shape, release the squeeze off tool. Where required, pipes can be given mechanical support to re-round.
This method is very effective for PE pipes, by allowing a controlled, complete shut-off of the system. It is also a relatively simple process to carry out. However, again the operatives should be suitably trained in the application and operation.
Pipe freezing
The line freezing method isolates a section of the pipeline by using liquid nitrogen to create an ice plug. This freezes the fluids in the pipe and halts their flow while repairs and maintenance are being carried out. After the work is done, the ice plug can be carefully thawed out in a controlled manner. This will allow normal flow to resume without damaging the pipe.
This freezing method can be effective for emergencies, where immediate repairs are needed without shutting down the system. Pipe freezing is usually operated by specialist contracting companies, when it comes to larger water distribution mains, however Hy-Ram do offer some smaller domestic and commercial equipment, for use on pipes up to 100mm.
However, line freezing is not suitable for all water pipes, it is important for skilled operatives to assess each project accordingly. It is also not recommended for pipes under high pressure or extreme temperatures.
Hot tapping and line stopping
When we discuss line stopping, hot tapping usually comes into the conversation too. They are two pipeline maintenance techniques that can be used without shutting down the whole system. Let’s dive into their synergistic relationship.
While line stopping temporarily halts flow through the pipe, hot tapping is used to create new connections branching off the main live pipeline.
The hot tapping process involves drilling a hole into the pipeline using a specialised cutting tool. Then, a new pipe section or valve can be attached. This procedure can be carried out while the pipeline remains under pressure and in service, ensuring that flow will not be disrupted.
Hot tapping and line stopping are two different processes for different purposes, but can be used in conjunction. Often, hot tapping is the enabler for the line stopping process. Starting with hot tapping to add another connection to the pipeline creates an access point for line stopping equipment to be applied.
These processes are often complementary; they work hand-in-hand to achieve simple pipeline repairs. Flow stopping requires an opening to get the tools into the pipeline safely. Hot tapping provides that safe, live access without flow disruption.
How can Hy-Ram help with line stopping?
Line stopping for pipeline maintenance is such a crucial process that requires high-quality tools and equipment. It’s essential that the pipes won’t be damaged, operate efficiently, and maintain flow while repairs can be carried out smoothly.
From pipe squeeze-off tools to pipe freezing kits, we offer a wide range of specialist flow stopping products at Hy-Ram. Each tool and piece of equipment is of high-quality and meets industry standards to ensure safe and effective use.
Need support with training for your teams? No problem – reach out to us and we can discuss further.
WASK Hydrant Wizard
Hy-Ram is a proud distributor of WASK equipment, a highly reputable developer of technical utility products.
The WASK 4” Hydrant Wizard is designed to flow stop water in 80mm/3” and 100mm/4” bore pipes, at up to 8 bar working pressure, without de-pressurising the main system. There is also now a 2” adaptor kit, facilitating the use on smaller assets.
The Hydrant Wizard is the ideal tool for line stopping hydrant risers where an isolation valve, such as our Sandwich Valve, isn’t present.
The Hydrant Wizard is robust, simple and efficient to use, and its secure connection ensures minimal water loss and disruption.
Aquastop
At Hy-Ram, we also stock WASK Aquastop equipment, a direct solution for line stopping. It’s designed to flow stop water in 80mm/3” to 200mm/8” nominal bore pipes. The Aquastop is best suited to cast iron, ductile iron, steel, PVC, PE and asbestos cement.
Aquastop equipment is user-friendly, with a proven track record since the early 2000’s and is now used globally. It uses specialist bag technology with Aqua Hydro® Bags which inflate using pressure from the host water main, in conjunction with the integral pressure pots, which are self-regulating for operator safety.
Overall, the Aquastop is a fantastic tool for planned maintenance on water networks, offering what is often described as a soft-close application due to the gentle inflation of the Aqua Hydro® Bags, taking shape around commonly occurring tuberculation or calcification within water mains, offering a strong and reliable alternative to fixed line stopping products such as stopple systems.
This brings a significant advantage to the water network, as the soft-close offers a significantly reduced transient effect on the network when compared to mechanical line stopping. This reduction/eradication of transient pressure effects can result in less network issues such as leaks, and other detrimental occurrences.
This soft-close design feature applies to both the Hydrant Wizard and Aquastop due to the innovative design of the equipment and bag technology.
Key takeaways
Line stopping is a fundamental aspect of pipeline maintenance and repair. It boasts many benefits – keeping workers safe and the system running without disruption. This is why it’s of critical importance that the equipment you choose should be high-quality and user-friendly.
With decades of experience, Hy-Ram is an industry-leading provider of quality line stopping equipment. Contact our expert team to learn more and discover which tools are right for you.
