---
title: "Temporary events and festival sites: portable water systems"
source_url: https://legionella.io/articles/temporary-events-and-festival-sites-portable-water-systems/
canonical_url: https://legionella.io/articles/temporary-events-and-festival-sites-portable-water-systems/
pillar: "Building Types & Use Cases"
summary: "Legionella at temporary events is a budgeting call: the cost drivers behind tankered storage, sun-warmed water and showers, and where spend pays back."
primary_keyword: "event site Legionella"
date_published: 2025-12-26
date_reviewed: 2026-06-26
author: "Legionella.io editorial team (REMOTE TECH LTD)"
reviewed_against: "HSE L8 and HSG274 guidance"
region: "United Kingdom"
license: "(c) REMOTE TECH LTD. Quote freely with attribution and a link to source_url."
---

# Temporary events and festival sites: portable water systems

A festival turns the usual Legionella problem on its head. Instead of forgotten water sitting still for months in a permanent building, you get freshly delivered water warming up in the sun, temporary showers that go from never-used to thousands of uses in a single weekend, and the whole system torn out a few days later. The control measures are not the expensive part. The expensive part is delivering them on a field, against a build deadline, with kit you hired.

So the honest way to budget water safety for a temporary site is to price the field conditions, not the kit list. That reframing changes which numbers matter.

## What the temporary set-up is actually fighting

Strip a festival water system back and it is a chain of warm-water reservoirs joined by hose. Water arrives by tanker or temporary mains connection, sits in bowsers, IBCs and storage tanks, then runs through long temporary pipe runs to standpipes, hand-wash stations, catering points and, at camping events, banks of temporary showers. Add the misting and cooling fans that appear the moment a heatwave is forecast, and you have assembled most of the aerosol-producing kit HSE flags as creating foreseeable risk [1].

Two conditions make Legionella a problem: warm, still water for it to multiply in, and a fine spray that lets it be breathed in. The illness comes from inhaling contaminated droplets, not from drinking the water [2]. A summer event delivers both halves at once. Hoses lying across an open field and tanks standing in direct sun drift into the growth range even though the water was wholesome when it left the depot, and the showers and misting fans turn that water into a breathable mist aimed straight at people's faces. The broad expectation is to keep stored cold water genuinely cold and any hot water genuinely hot - roughly below 20C and above 60C, with the temperature band in between being the part to design out [3].

The timeline makes it worse. Systems are filled and pressure-tested during the build, then stand full for days before the public arrives. Breakdown leaves water sitting in pipework and tanks while the crew is busy elsewhere. Both periods are easy to leave off the plan because nobody is technically "using" the site - which is precisely when the water is warming and going nowhere.

## Where the money actually goes

Price the budget in three buckets. The common mistake is funding the first, underfunding the second, and assuming the third will never happen.

- **Planned control cost - predictable, the part that gets approved.** A site-specific risk assessment for the temporary system, a competent water provider, potable-certified tankers and bowsers, insulated or shaded storage, pre-opening flushing and disinfection of the filled system, temporary shower units supplied with serviced and disinfected heads, and someone competent to take temperature checks across the event rather than only on the day it opens. This bucket scales with the number of outlets, the length of temporary pipework and how hot the forecast is.

- **Friction cost - the field tax, and the bucket nobody writes down.** None of the above is hard in a plant room. It is hard at 2am in a muddy field with no mains, a tanker that can only reach half the site, three different contractors who each think water is someone else's job, and a welfare crew of volunteers rotating every shift. Refill cadence has to be scheduled and chased so storage actually turns over. Records get written on a clipboard in the rain. This friction, not the kit, is where temporary sites quietly lose control.

- **Failure cost - low odds, severe landing.** An event is a mass gathering. If illness is linked back to your water, attendees have already scattered across the country, which makes the public-health investigation slower, wider and more public [4]. Expect investigation time, emergency action, scrutiny of your event licence, and reputational damage that outlives the line-up. You cannot put a credible single figure on that without inventing one, so do not - but its sheer asymmetry against the planned cost is the entire argument for funding the first two buckets properly.

The decision rule that falls out of this: **spend first where warm water, aerosol and crowds overlap.** A bank of showers and a row of misting fans in a heatwave is all three at once. That is your priority pound - ahead of, say, a third water sample on a constantly-running catering tap that is effectively flushing itself.

## Where the spend earns it back

The payback at an event is rarely a tidy percentage. It is avoided disruption and a defensible position if a case is ever traced to your site. Three moves give the best return for the money.

First, attack heat and stagnation by design instead of by chilling everything. Shading and insulating storage and keeping water turning over through scheduled refills is far cheaper than refrigerated bowsers, and it does more to keep the temperature out of the growth band. Capping or removing the dead legs and unused spurs that always appear in a hand-built system cuts the flushing burden for the whole show - the same root-cause logic that drives permanent-building failures, covered in [on stagnation](https://legionella.io/articles/neglected-water-systems-the-danger-of-stagnation/).

Second, treat the build as a commissioning job, not a plumbing job. A temporary system is effectively commissioned from scratch every event, so a documented fill, flush and disinfection before the gates open earns back its cost the first time you can show it was done. The thinking transfers directly from [on commissioning new systems](https://legionella.io/articles/commissioning-new-water-systems-preventing-legionella-from-day-one/).

Third, write the showers into the contract. Specify that hired shower units arrive with serviced, descaled heads and get a flush before public use, and the highest-aerosol, highest-exposure point on site stops being the one nobody owns.

## The site-specific call you still have to make

This is general guidance, not a control scheme for your event. The temperatures, refill rates, disinfection regime and monitoring frequency that are right for your site depend on your water source, the kit you hire, who is exposed and the weather - and a wet October beer festival in a hall is simply not the same risk as a 30C August camping weekend with open-air showers. Treat any figure here as a prompt to confirm with a competent person through a risk assessment of the actual temporary system, signed off before the build, not a number to copy across. That assessment should also name who makes the call on site when a reading drifts.

## Your next move before the next build

Pull last year's site plan and mark every point where water is stored or sprayed - tanks, bowsers, standpipes, hand-wash stations, catering, showers, misting fans. For each one, write the single sentence that turns a task into a control: why it exists, what reading or check is acceptable, and who acts when it is not. Take that marked-up plan to whoever signs the water budget, and to the contractor who fills the system, before the kit is booked. If even one spray point has no name against it, you have found this year's priority pound. The pitfalls that catch teams who skip this step are gathered in [on why control plans fail](https://legionella.io/articles/why-legionella-control-plans-fail-common-pitfalls/).

## FAQ

### Does Legionella control really apply to a system that only stands for a long weekend?
Yes. The duties under the ACoP L8 follow the water system and the people exposed, not the building's permanence [5]. A few hot days are enough for water to warm and sit, and a temporary system has more new joints, hose and aerosol points than most permanent ones. Short-lived is not the same as low-risk.

### The water was certified wholesome when the tanker delivered it - isn't that enough?
No. A clean delivery tells you the water was fine at the depot, not what happens once it sits in a sun-warmed tank or a hose lying across a field for two days. Legionella control is about the conditions after delivery - temperature, turnover and aerosol - which is why monitoring through the event matters more than the certificate at the gate [6].

### Do misting and cooling fans for the crowd count as part of water safety?
Treat them as a high-risk aerosol source, because that is exactly what they are - a spray of fine droplets aimed at a crowd. They belong in the risk assessment alongside showers, with control over the water that feeds them and how often the system is refreshed [1].

## Related reading

- [Commissioning new water systems: preventing Legionella from day one](https://legionella.io/articles/commissioning-new-water-systems-preventing-legionella-from-day-one/)
- [Why Legionella control plans fail: common pitfalls](https://legionella.io/articles/why-legionella-control-plans-fail-common-pitfalls/)
- [Neglected water systems: the danger of stagnation](https://legionella.io/articles/neglected-water-systems-the-danger-of-stagnation/)

## Sources

[1] HSE, "Systems most likely to create legionella risk". https://www.hse.gov.uk/legionnaires/risk-systems.htm
[2] CDC, "How Legionella Spreads". https://www.cdc.gov/legionella/causes/index.html
[3] HSE, "Hot and cold water systems". https://www.hse.gov.uk/legionnaires/hot-and-cold.htm
[4] UKHSA, "Investigation of Legionnaires' disease: cases, clusters and outbreaks". https://www.gov.uk/government/publications/investigation-of-legionnaires-disease-cases-clusters-and-outbreaks
[5] HSE, "Legionnaires' disease. The control of legionella bacteria in water systems - Approved Code of Practice and guidance (L8)". https://www.hse.gov.uk/pubns/books/l8.htm
[6] HSE, "Testing and monitoring your water system for legionella". https://www.hse.gov.uk/legionnaires/testing-monitoring-water-system.htm