Is water main renovation a more sustainable alternative to replacement?
By Gareth Harris – WRc Approved Manager
In the AMP8 draft determinations, Ofwat asserted that they want to triple the rate of main replacements and proposed an extra £297 million of funding to accomplish this. This means water companies should be aiming to replace nearly 8,000 kilometres (4970 miles) of mains from 2025 to 2030.
However, rehabilitation of exiting water mains could be a viable alternative that is up to 50% cheaper, emits up to 40% less carbon and can be completed up to 25% quicker, according to data from Yorkshire Water who completed a lining programme in AMP7.
In situ resin lining of water mains is not a new concept. In fact, water mains rehabilitation has been happening for over 50 years, but the development of the resins and lining equipment means that the process today is much quicker than it used to be. The early epoxy coatings required 16 hours to air cure, whereas today’s 1-hour cure resins allow a water main to be returned to service in a matter of hours following application.
But why do we need to rehabilitate water mains?
Many of our water mains were built in the 19th century. Although there is no ideal measure of asset health available, the data 
suggests that the age of mains in the water industry in England and Wales is, on average, around 60 years old. Furthermore, there is a long tail of assets that are considerably older than this, with nearly 25% of assets being more than 80 years old; and over 13% of assets being more than 100 years old, and even up to 150 years old.
Historically, one of the primary reasons for water main rehabilitation was water quality – using a non-structural lining to remove discolouration from drinking water. However, with water companies focusing on preventing leakage, modern semi-structural linings can increase an asset life by up to and beyond 50 years.
So, how does mains re-lining work?
The modern lining materials are a two-component polymeric resins, made up of a base and an activator, which are mixed on site and spray applied. The water main must first be thoroughly cleaned before the resin lining can be applied. The Drinking Water Inspectorate (DWI) must approve the resins and their Instructions for Use (IFU). The approved lining contractor must comply strictly with the IFU and Water UK’s Water Industry Specification, WIS 4-02-01, when applying the material. The resin lining can then be applied at the desired thickness, and, if necessary, in more than one layer to achieve the required thickness.
So, who can undertake in situ water main lining?
The operational and legal requirements for the in-situ resin lining of water mains are set out in Water UK’s Water Industry Specification, WIS 4-02-01. The WIS requires that only an approved contractor, who has been certified by a Nominated Certifying Body (NCB), undertakes the lining.
WRc is Water UK’s Nominated Certifying Body for WIS 4-02-01. This means that any contractor wishing to become an Approved Contractor for the in-situ resin lining of water mains must go through the UKAS accredited process. This involves evaluating the installation team’s knowledge, assessing the resin and rig combination and completing lining trials.
Once approved, the contractor will be subject to further lining rig performance audits (to be conducted at the start of each lining programme) to ensure the rig continues to apply the approved resin in accordance with the WIS.
To find out more about WRc’s role as the NCB, please visit WRc Certified service page. https://www.wrcgroup.com/services/wrc-certified-in-situ-resin-lining-of-water-mains/