Retrospective Evaluation of Cured-in-Place Pipe - (NEPIS)(EPA ...

with infiltration, whereas the driver in Singapore is to eliminate exfiltration. Whereas both use CIPP,
they have different views on its application and effectiveness.
Singapore makes extensive use of CIPP, alongside PVC spiral lining and PE fold and form lining. It has
stipulated epoxy-based CIPP for its smaller sewers and for laterals. More than 80% of the lining
undertaken to date is CIPP and this is expected to continue to be the case in current and future phases of
work. The specifics of the methods used have evolved to meet the needs of a tropical climate and the
rigorous performance requirements of PUB. As a result, PUB considers CIPP to be a viable, long-lasting
means of achieving a watertight sewerage system.
Göttingen’s city council decided in 1990 to make serious investments in the wastewater system with the
aim of achieving a watertight and maintenance-free system by 2035, including the privately-owned
laterals. Göttingen’s aim is a watertight system and, after 15 years of using CIPP, and some 15,000
watertightness tests, they consider that it is an excellent long-term repair method but will not provide a
permanent watertight system. This is due to problems of sealing ends at manholes and of sealing the
openings at lateral connections. CIPP can give a watertight pipe but not a watertight system. Göttingen
has switched its strategy to achieve complete system watertightness to aiming for a 100% PE system, with
welded joints throughout. When installing new pipe, only materials approved by the German Technical
and Scientific Association for Gas and Water (Deutscher Verein des Gas- und Wasserfaches e.V. -
Technisch-wissenschaftlicher Verein [DVGW]) for gas use are allowed to be installed. This is the reason
that since 2006, PE rehabilitation technologies have replaced CIPP at Göttingen.
Of the 36 km (22 mi) of CIPP installed in main sewers in Göttingen, 7 km (4.4 mi) has already been
replaced with PE and eventually all but approximately 10 km (6.2 mi) will be replaced. Taking the
DVGW approach means that the system is effectively being redesigned as a pressure-capable system
based on zero infiltration or exfiltration. As stated above, Göttingen now considers CIPP to be an
excellent long-term repair technology with a service life of 50 years and that can make individual pipes
watertight. But it does not meet their requirement of achieving a permanent, watertight network.
Thames Water is satisfied that its established system, using preferred contractors, delivers value for
money. This experience is considered important in eliminating installation defects which are the main
source of performance problems later on. Thames Water believes that in its geology the use of leaktight
systems is important to minimizing infiltration and accordingly epoxy resin linings may be required for
small diameters prone to leakage. It does not plan to change its policy on the use of CIPP.
The experience of Severn Trent Water has been generally good. They report some problems with liner
stretch, missed connections, and some wrinkling. They have also experienced problems in re-rounding
severely deteriorated pipe prior to lining. As with Thames Water, they do not plan to change their policy
on the use of CIPP.
The Agglomeration de Chartres uses CIPP to reinforce sewers where there is high risk of root penetration.
For structural problems, and even I/I, open cut replacement with ductile iron pipe is preferred. The
condition of lateral connections and frequent displaced pipes means that CIPP is considered ineffective in
combating I/I. CIPP is considered a maintenance activity rather than capital expenditure/asset renewal.
Nevertheless, Chartres expects to increase its usage of CIPP in the coming years, and to increase
rehabilitation at the expense of replacement in order to improve the network within its limited budget.
The Agglomeration des Hauts-de-Bièvre considers CIPP to be a reliable method that will remain the main
one used for sewer rehabilitation works. Good planning and pipe preparation are essential and nothing
should be left to chance. Experienced and knowledgeable consultants and contractors are also necessary
for successful installations. They now enter into annual contracts with one contractor only to ensure
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