Light curing in property drainage

Market overview and state of technology

The market for the rehabilitation of building and property drainage is developing dynamically. Especially due to the complexity of construction sites, the demands on sewer rehabilitation companies have increased enormously. In addition to the established curing processes (ambient temperature, steam and water) in the rehabilitation of property drainage pipes, curing with light has also established itself on the market in recent years. The rehabilitation companies are especially convinced by the short curing times and the associated economic advantages. But what are the real advantages of this system and what are the disadvantages?

Light curing for the rehabilitation of the property drainage

Frequently there are pipeline networks with many bends, differing dimensions and numerous inlets. As a rule, the exact course of the pipeline is not known prior to the measures, meaning that sewer rehabilitation companies must act with a high degree of flexibility. In addition, specified time windows, during which the rehabilitation must take place, are on the increase. Four different curing methods are available for the rehabilitation: light, steam, hot water and curing at ambient temperature. The experts agree – light curing is a perfect complement to the curing methods already in use, as the process offers some significant advantages.

Curing with light, ex. BRAWOLINER®
Curing with light, ex. BRAWOLINER®
Light curing in use
Light curing in use

Particularly noteworthy is the almost unlimited processing time. The result is a high degree of installation safety, as the vinyl ester resins used only cure when exposed to UV or LED light. Another advantage is that pre-impregnation of the liner is possible without any problems. The retraction speeds of the light sources can range from 0.5 to 1 metre per minute depending on the nominal diameter (e.g. DN 150 up to 0.5 m per minute). A 30-metre pipe can thus be cured very quickly in 30 to 60 minutes, which under certain conditions can significantly reduce the construction time.

Fields of application for light curing

Curing with the aid of light is particularly suitable on construction sites for property drainage where there are no or only a few inlets and branches at the connecting sewers. Good accessibility in the area of the starting point and ideally also of the destination point (e.g. shaft, inspection opening) are advantageous in order to be able to protect the connection area against penetration of water behind using e.g. collars or epoxy resin spatulas after completion of the shrinking process.

Figure shows area of the property drainage

Practical example – light curing in use

Rehabilitation task: Several road inlets, which were rehabilitated from the lateral sewer inlet to the main sewer.
Duration: approx. 1 hour
Material: BRAWOLINER® 3D DN 100-150
Curing method: light curing (UVRelining)
Brief description: A preliner was installed before the actual rehabilitation. The liner was then blown in and cured with the light curing unit within a few minutes. Afterwards the drain inserts were cut flush and integrated with fibreglass moulding.
The advantages of light curing are obvious here: the time window for flushing the pipe, installing the preliner and liner and curing was approx. 1 hour.
Executing company: PKT – Pader Kanal Technik – Rohr Frei GmbH & Co. KG

Disadvantages of light curing

Yet besides the economic advantages of light curing, there are also negative side effects.

With the systems currently available on the market, a (minimal) annular gap is created in a large number of rehabilitation projects. This is due to shrinkage processes caused by the resin used (e.g. vinyl ester resin), which means that the resin does not form a positive connection with the old pipe. The annular gap can allow water to get in behind. For example, groundwater and roots can penetrate between the outside of the liner and the inside of the old pipe. This can jeopardise the success of the rehabilitation.(see expert report "Support for sample construction sites - testing for freedom of penetration of water behind on different house connection systems" issued by the accredited testing laboratory for plastics in hose lining, Siebert + Knipschild GmbH 1)

Therefore, according to the generally accepted rules of technology, the integration of hose liners in the case of annular gap formation with e.g. liner end collars, swelling tapes or reaction resin systems is required.
(see DWA-M 144-3)

The resins used, such as vinyl ester resin, only cure on contact with light. This means that the resins do not harden in the soil and can therefore enter the groundwater when escaping into the soil. At the forefront of the hose liner process is a clean, safe and environmentally friendly rehabilitation. Environmental pollution should be avoided in any case. Against this background, the use of a preliner is particularly recommended when using light-curing equipment and light curing. This prevents uncured resin from entering the groundwater via damaged areas.

1) Expert report: support for sample construction sites – Testing for freedom from penetration of water behind on different house connection liner systems,
Report No. 19-210-02264-SB

Übersicht der vom DIBt – Deutschen Institut für Bautechnik zugelassenen Schlauchliner und der mit dem jeweiligen Schlauchliner verwendbaren, am deutschen Markt gängigen Lichthärteanlagen
Hose liner DIBt-approved Light system Light source
BRAWOLINER® 3D Z-42.3-566 UVRelining Ultraviolet light, LED
BRAWOLINER® 3D Z-42.3-566 BRAWO® LumCure/Ikarus Ultraviolet light, gas discharge lamps
BRAWOLINER® 3D Z-42.3-566 Sewertronics Ultraviolet light, LED
BRAWOLINER® 3D Z-42.3-566 other systems e.g. Star-Light 1) other Star-Light 1) Ultraviolet light, gas discharge lamps
PAA-F Liner Z-42.3-528 Blue-Light Blue light, LED

1) Possible applications and retraction speeds still have to be tested

PDF file "Overview curing process" for download

BRAWOLINER® – A hose liner for all curing methods

Today, sewer rehabilitators face great challenges on building and property drainage construction sites. Flexibility and speed are required to ensure that no construction time is lost. The choice of installation technique and curing method depends on the structure and condition of the sewage pipe, the drain pipe and the pipe network as well as the constraints on site. The requirements of the construction site determine the installation technique – not vice versa. With a hose liner for all curing methods, BRAWO® SYSTEMS offers its customers this required great flexibility, as every situation and requirement can be individually addressed on site. The BRAWOLINER® is a seamless textile hose with seamless film coating. Due to a special loop construction, all BRAWOLINER® hoses are extremely flexible, making them the ideal rehabilitation solution for defective pipes with dimensional changes and bends of up to 90°. Due to its high longitudinal and transverse expansion capability, the BRAWOLINER® adapts to the pipe run optimally and almost crease-free. Thanks to the approvals, all systems offered by BRAWO® SYSTEMS – including light curing – have been tested and approved by the DIBt (German Institute for Structural Engineering) and their high quality and safe use has been verified.

·        DIBt approval Z-42.3-362: "Hose liner method with the designation "BRAWOLINER®" for the rehabilitation of underground damaged waste water pipes in nominal widths of DN 100 to DN 250"

·        DIBt approval Z-45.3-499: "Hose liner with the designation "BRAWOLINER®" for the rehabilitation of damaged sewage, rainwater and collecting pipes inside buildings in the nominal diameter range DN 50 to DN 200"

·        DIBt approval Z-42.3-566: hose liner method with the designation "BRAWOLINER®" for the rehabilitation of damaged underground waste water pipes in the nominal width range from DN 100 to DN 225 with LED or UV light curing



The sewer rehabilitation companies agree: light curing is an economically viable addition to the existing portfolio of curing methods used in property drainage.

To ensure the environmental compatibility of light resins, the use of a preliner is recommended. This is the only way to ensure that any impact on the body of groundwater/soil is avoided.

The challenge is to further develop the technology so that the disadvantages of the curing method are minimised. For example, light-curing, styrene-free vinyl ester resins allow significantly faster curing times than cold/temperature-curing epoxy resins, but epoxy resins have proven themselves over more than 20 years with regard to avoiding penetration of water behind and due to their good mechanical properties.

Ultimately, the requirements of the construction site still determine the choice of the rehabilitation method.


Your contact person:
Candida Heinrich-Piras
Head of Marketing & HR
67659 Kaiserslautern
Tel.: +49 631 20561 - 280