Report No DWI0131

DETERIORATION OF ASBESTOS CEMENT WATER MAINS (MSS 9731 SLD)

Final report to the Department of the Environment

DWI0131

Dec l988

SUMMARY

I OBJECTIVE

The objectives of the investigation are:

  1. To determine the amount, size, age and geographical distribution of asbestos cement pressure pipe conveying potable water in the UK water supply system.
  2. To estimate the population supplied by water which has been conveyed through asbestos cement mains.
  3. To determine the rates of deterioration of asbestos cement pipe occurring in UK waters and the potential for release of asbestos fibres into the water supply.
  4. To assess the efficacy of measures which could be taken to reduce the deterioration of asbestos cement pipes or prevent further release of fibres.

II REASON

The recent interest in asbestos in the environment has resulted in questions being raised over the suitability of asbestos cement pipes for conveying potable water. A recent study commissioned by the Department of the Environment has concluded that asbestos cement pipes may contribute to the numbers of asbestos fibres in the conveyed water in the distribution system, and suggests that the aggressiveness of the water and the length and age of the pipes are contributory factors.

III CONCLUSIONS

  1. Asbestos cement usage
  2. Deterioration
  3. Failures/Degradation rate
  4. Protection

IV RESUME

Water utility records have been examined to determine the amount of asbestos cement pipe in use in the UK water supply system. The data has been analysed to identify the size, age and geographical distribution of AC pipes. An assessment of the population served has been made. Failure data from four selected areas were analysed and show a failure rate below the national average for all pipe materials. Various trends have been identified in the failures from each of the areas, and possible reasons for these trends have been proposed.

Examination of pipes exhumed from a wide variety of environments showed attack to be non uniform due to the presence of a bitumen coating. Because of this non-uniform attack no simple model could be determined to explain the deterioration, although reasonably good correlations could be made for low pH, low alkalinity waters. It is thus not possible to accurately predict potential rates of release of fibres into the water supply.

Cement mortar and epoxy resin protective linings were successfully applied to asbestos cement pipes in various conditions of degradation. Accelerated corrosion tests were developed to determine the efficacy of these protective linings. The tests provided an acceleration of approximately 10 compared to the most severe degradation observed from exhumed pipe samples, thus 12 months exposure to the accelerated tests approximates to a 10 year service exposure.

Short term tests examining the effect of modifications to the chemical characteristics of the water were undertaken to assess whether protection could be afforded by treatment of the conveyed waters.

Copies of this report may be available as an Acrobat pdf download under the 'Pre 2000 Reports' heading on the DWI website.