Summary of Findings
It is understood that the Council is considering the removal of the water tanks at the allotments on the basis that they constitute a health hazard, presumably that they are a potential cause of legionnaires disease? In the opinion of the plot holders, while there is evidence that water butts can potentially pose a threat to health, water tanks do not.
Removing them is not only unnecessary but would significantly affect plot holders and increase water usage (and hence the cost) by the much greater use of hosepipes.
Scope
This note deals with the four originally deployed tanks. The small tank near plot 7a is dealt with in the appendix.
Terminology Used
A water butt is a container on an allotment plot which is typically used to collect rainwater, although on some allotment sites it may also be fed by mains water. In either case, the water in the butt is for the sole use of the plot holder whose plot it sits on.
A water tank, as deployed at our allotment site, is fed by chlorinated mains water and is shared by multiple plot holders. It is sometimes called a dipping tank.
History
The water tanks were first installed around 1990. The Council has never carried out any work on them with respect to hygiene. Around 2008/9 the plot holders emptied and cleaned them. They were all fairly disgusting: the worst by far being the tank near the seat which had at least six inches of silt / soil in the bottom, along with pieces of brick and other assorted objects.
From memory, each tank has been emptied and cleaned over the winter period on a total of five occasions. In intervening years, they have been dredged to remove any silt, although plot holders are encouraged to clean crops and tools in a bucket of water, not in the tank.
The plot holders have also installed covers on each tank which helps to stop: birds getting at them; leaves et cetera from falling in; and the potential growth of algae.
Understanding of Legionella
Legionella is present in most soil and aquatic environments and generally causes no harm. Studies have shown that it has been found to be present in many water butts, particularly if the water is stagnant and notably when the temperature of the water is between 20C and 40C. The danger occurs if a hosepipe is used to extract the water from the butt when it is possible to inhale droplets which can get into the lungs and potentially result in legionnaires’ disease. However, using a watering can, rather than a hosepipe, significantly reduces this risk.
I have not been able (so far) to find any studies which cover the situation where shared water tanks that are fed by chlorinated mains water are in operation rather than water butts. Possibly, they are not considered to be an issue?
Our Site
Observations include:
- Shared water tanks, filled by chlorinated mains water, are used, not water butts
- The tanks are used to fill watering cans quickly and easily
- Hosepipes, when used, are fed directly from the pipe; that is the water does not go via the tank
- The water could not be described as stagnant during the growing season, as the tanks are shared and in fairly constant use. From late October to late March when the water supply is turned off, the chlorine level will be effective against any bacteria given the modest temperatures
- The covers on the tanks improve hygiene.
Effects of removing the water tanks
They include:
- More plot holders will resort to using a hosepipe, leading to a significantly greater use of water (and hence cost)
- A greater use of hosepipes will lead to reduced water pressure when multiple plot holders are watering. In this situation, existing standpipe users will probably suffer more for the simple reason that their taps are furthest their away from the pipe that brings the water into the site from Church Road
- Greater queuing for a standpipe .. how long is a typical hosepipe session?
- No water will be available during the winter. There is occasional need for water during the period when the supply is turned off. Examples include: the watering in of newly planted bushes and the like; and dry conditions which sometimes occur in early spring or late autumn when the water in the tanks helps to fill the gap
- Hosepipe bans, becoming ever more likely, will make watering extremely difficult, if not impossible for some. Growing on a sandy soil is difficult enough as it is
- And finally, holding a watering can under a tap can be difficult. We have (and had in the past) plot holders with tendon problems, arthritis and “weak arms” (a phrase employed by one ex-plot holder) who can struggle to hold a watering can while it fills. Dunking a can quickly into a tank is more bearable for them.
Legionella Assessments
There are professional organisations that carry out legionella reviews. Has such a review been carried out here? If so, can we please have sight of the report? It would of course be useful to know of any improvements that can be made at our site.
Advice to plot holders
As mentioned in some of the links that are given below, it is recommended that hosepipes should be emptied after use, primarily so that water which may otherwise collect at either end, does not have a chance to heat up.
As previously recommended, plot holders should clean crops and tools in a bucket of water, not in a tank.
Links
Here are some relevant links that we have located. Has the Council found any others?
Are Garden Water Butts Contaminated with Legionella Bacteria? (legionellacontrol.com)
Minimising health risks in the garden / RHS Gardening
HSE – Legionnaires’ disease – Are there Legionella risks in my workplace?
On further investigation, here are some additional links which might loosely be described as general guidance on health and safety on allotments. It also includes a useful article on water usage from the National Allotment Society.
National Allotment Society – Health and Safety on Allotments
National Allotment Society – Water Use on Allotments.
Hart Allotments – Health and Safety Guidance – General Safety for Plotholders
Clophill Parish Council – Health and Safety Guide to Allotments
Social Farms and Gardens – Allotments Management Toolkit: Health and Safety on Allotment Sites
National Allotment Society – Water .. What do you need to know? (scanned copy)
Appendix – Small tank near plot 7a
A larger second-hand tank with no cistern was installed near plot 7a in 1990. Perhaps the available funds ran out? It quickly developed some holes due to rust, and it was therefore rendered useless.
As part of a project in 2008 to extend the water supply round to plot 2/2a where a standpipe was installed, the Council replaced this tank. Unfortunately, a much smaller tank was installed which only holds 200 litres, whereas the other four tanks each hold approximately 400 litres.
A cover was added by plot holders, although it appears to have gone missing. Notwithstanding the cover, the water in this tank tends to go green with algae. This may well put plot holders off from using it, thus making it even greener.
Possible solutions here include:
- Ideally, replace the tank with one that is similar in size and capacity to the others
- Fit a cover (either the existing one or a replacement)
- Periodically apply a water cleaning product, e.g. Envii.
BK
Version 1.2 – February 8th, 2024
Version History
| Version | Date | Notes |
| 1.0 | June 26th, 2023 | First official version, following on from several drafts. |
| 1.1 | July 2nd, 2023 | Added links to health and safety info from NAS and others. |
| 1.2 | February 8th, 2024 | Link to generally useful article on water regulations in NAS Allotment Gardener Magazine issue 1 2024. |
BK .. This and That 