Report No FR0076

A SURVEY OF SCOTTISH WATER QUALITY
AND ITS CORRELATION WITH 'PEPPER POT' PITTING

FR0076

Mar 1990

SUMMARY

I OBJECTIVE

To collect and statistically analyse retrospective water quality data from various sources in Scotland and attempt to correlate any changes with the recent outbreak of pepper-pot pitting.

II REASON

Since the early 1980'5 the copper piping in a number of large properties in Scotland have been suffering from a new form of corrosion known as 'pepper-pot' pitting. As part of a larger research programme to identify the causes and to help give advice on preventative measures, WRc has undertaken to determine the role, if any, of water quality.

As part of WRc's programme a survey of the waters feeding various Scottish pitting and non-pitting properties has been undertaken.

III CONCLUSIONS

  1. Due to the limited amount of data available in Scotland for the time period of interest, it is only possible to examine in detail the effect of a few water quality parameters on copper pipes.
  2. No change in any water quality parameter examined could be consistently correlated to the pitting behaviour of copper pipework in Scotland.
  3. There are no obvious discontinuities in the data which might account for the initiation of copper pitting, although any transient changes may have been missed due to the nature of the survey.

IV RECOMMENDATIONS

Until a clearer idea as to the mechanism of pepper pot corrosion is developed, it is recommended that no further survey is undertaken.

V RESUME OF CONTENTS

The report gives analytical results obtained from waters supplied to various hospitals for up to 15 years. Some of these hospitals are now experiencing copper pitting. The significance of any changes in water quality in promoting this attack is discussed.

Copies of the report are available from FWR, price 25.00, less 20% to FWR Members.