THE LONG TERM MIGRATION OF
SUBSTANCES FROM IN-SITU APPLIED EPOXY RESIN COATINGS
Trials of epoxy resin relining for the rehabilitation of water mains in
the UK started in the late 1970s and by the late 1990s epoxy lining had
become the most popular nonstructural rehabilitation method. Currently
five manufacturers hold approvals for epoxy resins for the in-situ
lining of water mains.
The Committee on Products and Processes for use in Public Water Supply
(the CPP)1 noted that there is a lack of
leachate data from in-situ relined pipes after varying periods of time
in service. Whilst the use of epoxy resins for mains rehabilitation is
declining, the long service life of these products (of the order of 30
years or longer) means that applied linings have the potential to
affect water quality for decades. To fill this gap in leachate data,
DWI appointed WRc-NSF to examine the leaching of chemicals from
existing epoxy resin in-situ relined water mains based on samples taken
from consumers’ taps. (1
The CPP was disbanded in March 2007.)
Initially the existing information on leaching from epoxy resins was
reviewed. The review covered pre-approval test results, audit test
results and any other relevant information.
Water companies were contacted to attempt to identify suitable zones
for sampling covering all combinations of: five epoxy resins; hard and
soft water; low and high free chlorine concentration; and three ages of
linings – 1-2, 3-6 and 7-10 years. It was not possible to
identify sampling sites covering all possible combinations. A sampling
plan was devised to cover as many combinations as possible –
this included eight water undertakers’ areas of supply. Two
sets of samples were taken – the first during April to May
2006 and the second during August to September 2006, when water
temperatures were warmer. Most of the locations sampled in the first
phase were included in the second phase of sampling. A total of 120
samples, including field blanks, were taken.
Suitable streets for sampling were identified in consultation with
water company staff. Samples were taken from domestic drinking water
taps. The tap was fully opened and the water run to waste for at least
three minutes to flush water that had been standing in the domestic
pipework. Samples were taken for Total Organic Carbon (TOC) and general
survey Gas Chromatography – Mass Spectrometry (GC-MS)
analysis. After the samples had been taken the free chlorine
concentration was determined using a test kit and the water temperature
was measured using a digital thermometer. These readings, together with
the address of the property and other pertinent information, were
recorded. In each water supply zone, at least one field blank sample
was taken. The blank samples were
taken upstream of any relining.
The average water temperature
during Phase 1 was 11 °C and during Phase 2 this had risen to
16.5 °C. Samples were assigned to the
‘High’ and ‘Low’ chlorine
category in relation to the median chlorine concentration.
There was no technically or statistically significant difference in TOC
results between the samples and the field blanks for either phase of
sampling. This suggests that any leaching from the pipe linings is at a
The GC-MS results for Resins A, B, D and E did not show any evidence of
leaching of components of the resins. The chemicals detected were those
that are commonly found in drinking water samples; i.e. disinfection
by-products and environmental contaminants such as phthalates. Overall,
there does not appear to be a real difference between the results for
samples and field blanks in the case of these resins. Repeat sampling
during warmer water temperatures did not indicate any substantial
change in leaching characteristics.
Evidence of leaching of 4-t-butylphenol (4-TBP) from Resin C was found
– 4-TBP and various halogenated derivatives were detected in
some (but not all) samples taken from taps fed from mains
lined with Resin C. The highest concentration of 4-TBP found was 2.2
μg/l. Resin C is the only one of the five resins considered that
contains 4-TBP as a component.
Comparison of the review of results from laboratory tests and the field
survey indicates that laboratory test results may overstate the
leaching of components from epoxy resins.
Copies of this report may be available as an Acrobat pdf download under the 'Post 2000 Reports' heading of the Research Page on the DWI website.