Private water supplies are still a source of concern - and disease - David Clapham claims the time has come for a fresh approach to the problem and invites other environmental health practitioners to join the call for change

Private water supplies are often contaminated with human or animal waste several times during the year. More than 70 per cent of domestic private supplies are found to be contaminated when tested correctly and this can lead to outbreaks of illness. Reported illnesses are much lower than actual cases and there are a number of reasons for this. Even households with treatment are still at risk, as existing in-house treatment will not remove Cryptosporidium. In addition, many treatment systems do not work, generally due to a lack of maintenance.

The Private Water Supplies Regulations 1991 have been in force for over eight years. When they were introduced, they attempted to improve the testing of private water supplies by local authorities through the introduction of sampling uniformity across the country. There is no indication that they have been effective and they are now outdated and subject to routine criticism. With the introduction of a new European Directive on Water (the first since 1980) and in view of the body of useful research that has been carried out since the regulations were introduced, the time has come for new regulations. In addition, local authorities have to examine everything they do within the context of best value and the real value of the work they are doing with private water supplies needs investigating.

Existing sampling is inadequate and inconclusive, it underestimates the number of failures and increases "false positives". This leads to contaminated water supplies being given a clean bill of health. This in turn stops necessary water treatment being put in and reduces the number of supplies being connected to the mains. Any attempt at drawing conclusions from national sampling will be doomed to failure due to this problem of inconclusiveness with sampling. The results can only be used to note trends or confirm information that is already well known. They cannot be used to give an accurate picture of what is happening.

UNRELIABLE
Nil results from present day sampling of private water supplies cannot be a reliable indicator that a water supply is free of pathogens. There are three reasons for this:

• False positives because the sample was taken at the wrong time, ie sampling was not allied to rainfall.
• A "high risk zero". This is where there is a good likelihood that another sample taken just before or after the one analysed or taken at the same time from a different part of the water supply would be positive. Research has shown that this is statistically highly likely to occur in private water supply sampling.
• The main indicator organism (faecal coliform) does not correlate to the presence of Cryptosporidium and other pathogens. Due to their longevity, these may be present when the faecal coliforms have died off.

Results of sampling from a private water supply change from hour to hour, and day to day. Different results will be achieved when sampling at the source, the inlet, the outlet, at the tap and within a storage tank. Results will be different if the sample is taken from different places in the storage tank. How can any of them therefore, be representative of the supply itself?

Bacteriological contamination is not an abstract concept. Over 70 per cent of people using domestic private water supplies are drinking diluted animal or human faeces at some time during the year. Studies have shown that where treatment is installed, fitting and maintenance is so poor that 12 per cent fail the standards for bacteriological contamination. Twelve per cent of supplies with treatment are therefore potentially infected due to containing diluted animal or human faeces that have not been inactivated by treatment.

BAD TRIP
Holiday homes and campsites are often on private water supplies. When people are constantly drinking contaminated water from private water supplies, they may become immune to the micro-organisms in the water. They will only become ill when they drink a new organism from a new animal in the field or a new illness breaks out among the herd grazing near the source. Campsites contain transient populations who do not have this immunity and are therefore more likely to become ill. Often the supply may not be associated with an outbreak of disease.

The population will move on before the illness starts or blame something else, such as different foodstuffs or "holiday tummy" for the illness. This is exacerbated if only part of a group is affected (children drinking cordials diluted with water rather than adults drinking boiled water beverages). Even so, Category Two supplies, such as campsites are most often associated with outbreaks of waterborne illness.

The other point to make is that even if the sampling results were made known, the information we have on the efficiency of sampling regimes would not guarantee that the water was safe to drink. A new approach to private water supplies is needed. One that moves away from a local authority trying to show that the supply fails the standards for cleanliness, using deeply faulted methodology, to one that accepts that supplies will contain faecal material at some time during the year to a greater or lesser degree.

What do we propose?
With this in mind, a conference for environmental health officers has been organised to look at the state of the present knowledge and past experience. It should work towards detailing the necessary contents of a new and improved set of regulations. The new European Water Directive requires that these regulations be ready by the end of this year. Rather than just waiting for a consultation document, we should decide what we consider would be best and what is necessary for the safety of users of private water supplies and let the DETR know.

The conference will be held in Leeds on the 18 July 2000 by Aqua Enviro Technology Transfer, the University of Leeds-based environmental health organisation. Sponsorship has been obtained from the Drinking Water Inspectorate to reduce admission costs to a minimum (£65.00 plus VAT) in order to encourage a large number of delegates. The timetable includes adequate space for a detailed discussion in order to obtain the views of participants. After the conference, the ideas brought forward will be pulled together and forwarded to the DETR and the CIEH.

If you are interested in attending please contact Sarah Hickinson at: AE Technology Transfer, School of Civil Engineering, The University, Leeds, LS2 9JT. Telephone 0113 2332308; fax 0113 2603881; e-mail: sarah.hickinson@aquaenviro.co.uk

For more information on Cryptosporidium, visit the CIEH website at www.cieh.org.uk/crypto/