D is for... Double Containment

  • March 9, 2021

Double Containment

Double containment piping is by no means a new concept to process piping applications.  Systems using a carrier pipe with secondary containment have been installed using metal pipes for many years.  

DuoSafe® PVC-U and PVC-C double containment systems are designed for ease of installation.  

DuoSafe® FLEX is manufactured for dosing applications.  

Poly-Flo is a unique system using specially extruded twin wall pipes and injection moulded twin-wall fittings.  

AGRUSAFE double containment is a fabricated system produced in a wide range of sizes and in a variety of material combinations.  

Durapipe P-LX fuel systems are designed to safely convey petrol, diesel and fuel oil in below ground applications while ensuring harmful emissions cannot escape into the environment. 

AGRUSAFE Sure Grip® liners can be used to form single or twinwall linings for concrete structures and tanks.  

Application Guide  

√ Piping systems in the nuclear, gas, petroleum & chemical industries

√ Transporting dangerous fluids

√ Protecting ground water

√ Above or below ground use

√ Choice of materials including PVC-U, PVC-C,  PE, PP and PVDF 


duosafe tee

DuoSafe systems are manufactured from rigid PVC-U or rigid PVC-C, with containment pipe options including grey or clear PVC-U, PVC-C, ABS or Polyethylene.

They are ideal for above or below ground double containment such as applications found in chemical dosing lines, or to handle a wide range of acids, alcohols, salts and halogens. They are lightweight, rigid and easy to support. DuoSafe PVC-U is suitable for working temperatures up to 60°C. DuoSafe PVC-C may be used at higher temperatures - up to 100°C.

DuoSafe systems are designed for easy installation. Easy access is given to make the first joint on the inner (carrier) pipe, before making the final joint on the outer (containment) pipe. Assembly is faster and joints are more secure. DuoSafe systems are also assembled using a unique solvent cement - Weld-On 724 - which guarantees strong integrity with a wide range of aggressive chemicals.

A second significant benefit is the ease by which pipe cut lengths can be determined using a simple calculation based on the face-to-face measurement between the fittings to be connected. Installation becomes quick and easy. 

Several options on pipe pressure ratings are available - up to a maximum 16 bar. For reasons of economy it is usually also possible to reduce the pressure rating of the containment piping without affecting the system integrity.

Systems are available in PVC-U using inch sized piping. It can be specified in the standard dark grey colour, or with a clear PVC-U containment pipe to provide continuous visible monitoring of the system. Additional containment pipe options include ABS, for improved strength on above ground systems.

DuoSafe PVC-C is manufactured in inch sizes in light grey with the option of a clear PVC-U containment pipe.

DuoSafe® Flex

duosafe flex

DuoSafe FLEX is engineered for applications where long, continuous lengths of small diameter pipe is required. It is ideal for dosing applications such as in water treatment where there may be multiple dosing points drawing from a single chemical storage unit. 

DuoSafe FLEX is developed in conjunction with Copely Developments - one of the pioneers in the development of flexible pipe systems, and the inventors of the first open mesh PVC hose in 1950.

The system uses high quality flexibles that are manufactured as double contained products in a single extrusion process. They are supplied either in standard coil lengths of up to 300 metres, or may be cut to specific shorter lengths or specially manufactured in longer coils should the job require it. Connections between lengths or at termination points are made using a special range of rigid PVC-U fittings.

There are two types of flexible carrier hose available - Aquachem and Hydrachem - each offering strong resistance to a wide range of dosing chemicals. The carrier (dosing) tube is manufactured in sizes from DN 6mm up to DN 38mm, with a maximum working pressure of 10 bar.



The Poly-Flo system is a unique product. Manufactured in a patented process, it uses rigid pipes that are extruded as a twin-wall product together with twin-wall fittings that are injection moulded as a single item. 

The first benefit from this process is the minimisation of the space required for the containment pipe. Unlike all other rigid systems - that require the size of the containment to be large enough to pass through the carrier pipe and fittings - the unitary construction allows for a significant overall reduction in size.

Poly-Flo is also extremely easy to cut and weld, making installation relatively inexpensive. The carrier pipe and the containment pipe are butt-fusion welded in a single, simultaneous process that gives reliable joints between pipes and fittings.

The Poly-Flo range also includes a number of fittings that are not available in other double containment systems - most notably flanges to enable systems to be prefabricated or to be disassembled.

Manufactured from black Polypropylene and black PE100-RC, this system is ideal for applications such as laboratory waste systems or pressurised transfer lines. Typical installations are in waste treatment, carrying sulphuric acid or caustic soda, for bulk storage chemicals such as sodium hydroxide and aluminium nitrate; and in semi-conductor plants, handling sulphuric, nitric, and hydrofluoric acids for wet stations. The black Polypropylene and Polyethylene materials also offer a high level of resistance to UV when installed outdoors.

Poly-Flo is available in carrier pipe sizes 32mm, 63mm and 110mm. The assembled system has a fully pressure rated carrier pipe and containment pipe, suitable for use at working pressures of up to 6 bar.



AgruSafe double containment is fabricated from seperate pipes, and is available in Polypropylene, PVDF, Polyethylene and ECTFE (Halar). It is manufactured by AGRU - using the latest production and fabrication techniques to ensure maximum system integrity.

The systems may be assembled using the same carrier and containment materials, or they may also be ordered with dissimilar materials for reasons of economy or perhaps to suit a particular application.

AgruSafe is available with carrier pipe sizes as small as DN 25mm, however it is especially suitable for larger diameter systems. The standard range features carrier pipe diameters in sizes up to DN 250mm, but it is commonly manufactured in larger sizes up to DN 600mm. It is ideal for industrial and process waste lines as well as for pressurised transfer piping. Typical applications are found in pharmaceutical and semi-conductor plants, steel mills, plating shops, or in the chemical and nuclear industries.

There are two separate welding techniques used for AgruSafe systems: simultaneous welding and cascade welding.

Simultaneous welding uses the standard butt-fusion welding technique and is used where carrier pipes and containment pipes of the same material are used. The twin walls of the pipes and the fittings are welded together during the assembly process so that they can be clamped as one piece in the butt-fusion welding machine. Welding of the carrier and containment pipe takes place simultaneously.

The cascade welding technique is required when the carrier and containment pipes are from different materials. Cascade welding requires a specially adapted butt-fusion welding machine with a split welding plate so that the carrier pipe can be welded first. Once this is done, the outer shell of the welding plate is moved into position so that the containment pipe can be welded. Welding machines for both systems are available for sale or for hire.

AgruSafe systems are available in a variety of pressure ratings - up to PN16 - to suit the application. Using the wide range of pressure rated pipe and fittings - for example PN 3.2, PN 6 or PN 10 - it is possible to optimise the cost effectiveness of the system. 



Durapipe PL-X is a high performance, fusion welded, multi layered PE pipe system, supplied as a Secondary Containment product range specifically designed for safe transfer of fuel based liquids.

All products are made from virgin polyethylene of high density (PE80 or PE100). The pipe is a composite material co-extruded with a polyamide liner using the latest extrusion technology, resulting in consistent and technically superior performance.

The tough outer layer of Polyethylene provides excellent resistance to abrasion, mechanical and physical abuse and is corrosion and maintenance free. The highly visible bonded polyamide bore layer completes the composite pipe structure ensuring permeation, low absorption and dimensional stability. Impermeable to diesel, fuel oils and their vapours, Durapipe PLX exceeds the requirements of international standards and provide complete security against fuel loss.

Additional security against accidental fuel loss is achieved by using Durapipe PLX pipe systems. durapipe PLX exceeds the industry requirements regarding secondary containment of pressurised fuel delivery systems and provides an opportunity for continuous interstitial monitoring.

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