Report No DWI0785

Oct 1988

To identify the nature of water quality problems caused by in-situ cement mortar lining with ordinary Portland cement (OPC), and to identify the areas where these problems arise.

II REASON

Cement mortar lining is widely used to rehabilitate corroded water mains throughout the United Kingdom. In some instances pH and aluminium levels of water passing through newly lined mains can be elevated above the EC directive maximum limits. The Department of the Environment has commissioned WRc to investigate the effect that cement mortar lining has on water quality.

III CONCLUSIONS

The use of OPC as a material for lining small diameter dead end mains with low flows can give rise to problems with the conveyed water quality. These problems vary in degree and duration depending on the type of water in the distribution system. In very low alkalinity waters (around 10mgl^-1 CaCO₃) pH levels can be elevated above 9.5 for several years and aluminium levels can be above 0.2mgl^-1 for between 1 and 2 months. In low alkalinity waters (around 35 mgl^-1 CaC0₃) the water quality problem is restricted to an increase in pH levels above 9.5 for up to a month. In waters with an alkalinity greater than 55mgl^-1 CaC0₃ there is no adverse effect on water quality after the first week following relining.

IV RESUME

A series of field trials were carried out throughout the UK in areas of differing water qualities. These trials were designed to investigate the effect that lining mains with ordinary Portland cement had on the conveyed water quality.

Copies of this report may be available as an Acrobat pdf download under the 'Find Completed Research' heading on the DWI website.