---
title: "Electric showers and Legionella: risk, cleaning and what landlords should know"
source_url: https://legionella.io/articles/electric-showers-and-legionella-risk-cleaning-and-what-landlords-should-know/
canonical_url: https://legionella.io/articles/electric-showers-and-legionella-risk-cleaning-and-what-landlords-should-know/
pillar: "Building Types & Use Cases"
summary: "Electric showers heat cold mains on demand, so storage risk is low - but the head still sprays warm aerosol. How to clean, flush and assess it proportionately."
primary_keyword: "electric shower Legionella"
date_published: 2026-03-28
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."
---

# Electric showers and Legionella: risk, cleaning and what landlords should know

An electric shower has no hot water tank behind it. It heats cold mains water as it passes through, on demand, only while someone is using it. That removes the thing most people picture when they think of Legionella: a warm stored reservoir sitting at growth temperature between uses. On that count an electric shower is genuinely lower-risk than a shower fed from a cylinder or a calorifier — much like a combi boiler, there is no large body of tepid water waiting to be colonised.

But the risk that matters with any shower is not where the water is heated. It is what comes out of the head.

A showerhead breaks water into a fine spray, and that breathable aerosol is the route by which Legionella reaches the lungs and causes disease — you have to inhale it, not drink it [1]. The electric unit itself never gets near a disinfection temperature; it warms cold water to something comfortable and pushes it straight into a head and hose where scale and biofilm can settle. So the heater is the reassuring part of the picture. The head, the hose, and the cold supply feeding them are where attention belongs.

## Why the showerhead is the focus, not the unit

Start with how the bacteria reach a person. Legionella does not make anyone ill by being swallowed. It has to be inhaled as an aerosol — the cloud of tiny droplets a running shower throws into the air and that drift far enough to be breathed deep into the lungs [1]. A bath tap filling a tub barely aerosolises. A showerhead is engineered to do exactly that. This is the same reason a domestic shower is the one outlet worth taking seriously even in a low-risk home, a point covered in [Can you catch Legionnaires' disease from your home shower?](https://legionella.io/articles/can-you-catch-legionnaires-disease-from-your-home-shower/).

Now think about what an electric shower actually delivers. It blends to a pleasant temperature at the head, often somewhere around 38-42°C — squarely inside the 20-45°C band where Legionella multiplies most readily [2]. The flow is brief and intermittent: a few minutes a day at most, sometimes far less in a spare bathroom or a flat sitting empty between lets. Between uses, the water trapped in the head and the flexible hose sits still and warm. Add the limescale that electric showers throw off freely in a hard-water area, plus the biofilm that clings to that scale, and you have a small, sheltered surface for bacteria to settle on at the exact point where water becomes breathable.

That is the whole mechanism. The unit cannot disinfect what passes through it, and the warm spray it produces is the hazard. So the controls are simple to state: keep the head and hose clean, and keep the cold water behind them moving and cool.

## Cleaning and descaling the head and hose

Because the head and hose hold the risk, they are what you clean. Dismantle the showerhead, soak it to shift the limescale, brush out the individual nozzles where scale and slime collect, and rinse it through before refitting. The flexible hose matters too — a kinked or sagging hose holds a slug of standing water, and the rubber-lined bore is a comfortable home for biofilm. Where a hose is heavily furred or perished, replacing it is cheaper than fighting it.

How often? Frequency is set by your risk assessment and the local water, but cleaning and descaling roughly every three months is the common benchmark for showerheads, brought forward in hard-water areas where scale builds fast [4]. The descaling schedule and the practical method are set out in more detail in [Showerhead cleaning and descaling schedules](https://legionella.io/articles/showerhead-cleaning-and-descaling-schedules/). The honest point is that in a soft-water flat used daily, a clean head and a habit of running the shower may be the entire control regime — and that is fine, because it matches the actual risk.

## The void between tenancies: the classic risk window

The single most important moment for an electric shower is not when it is in use. It is when it has not been used.

A property standing empty between tenancies is the textbook scenario. The mains supply to the flat carries on warming gently to room temperature, the cold feed to the shower stops being cold, and the water sitting in the head and hose drifts into the growth band and stays there for days or weeks. Then a new tenant arrives, turns the shower on, and the first thing it does is aerosolise whatever has been multiplying inside it.

The fix is undramatic and effective: before anyone uses a shower that has been standing, run it. Run the cold supply through first to displace the stagnant water, then run the shower itself to clear the head and hose, ideally with the head removed or held low so the run does not generate a spray of the very aerosol you are trying to flush away, and the room well ventilated. The aim is to push the still water out and pull fresh, cool mains water through before the outlet is used normally [3]. This is why "flush before re-letting" appears on every landlord checklist worth the name.

## Landlord duties: proportionate, not over-engineered

Landlords have a legal duty to ensure the risk of exposure to Legionella for tenants and visitors is assessed and controlled [3]. That sentence frightens people into buying things they do not need, so be clear about what it actually requires.

It requires a risk assessment. It does not require, for most domestic rentals, an elaborate one. The HSE is explicit that in many residential settings a simple assessment will show the risks are low and no further action is necessary beyond keeping the system in good order [3]. A small flat served by mains-fed electric showers, used regularly, with no stored hot water, no cold-water storage tank, and no long dead legs, is close to the lowest-risk water system a building can have. The proportionate response is a written assessment that records those facts, sensible cleaning, and flushing after any void — not a quarterly contractor visit and a sampling regime designed for a hospital.

There is no legal requirement for a "Legionella certificate", and no requirement to use an external consultant if you are competent to assess a simple system yourself [3]. The wider duty-holder framework for rented homes is covered in [Landlord responsibilities for Legionella in rental properties](https://legionella.io/articles/landlord-responsibilities-for-legionella-in-rental-properties/), and the practical control measures across a let portfolio in [Legionella control in residential rental properties](https://legionella.io/articles/legionella-control-in-residential-rental-properties/).

The pragmatic call, in my view: assess once, properly; record it; then make the recurring actions — the descale and the void flush — routine and visible, rather than commissioning expensive work the risk does not justify.

## A practical checklist for electric-shower properties

Three short lists for three different moments. Treat each item as something to do and then record.

**Routine cleaning (every property with an electric shower)**

- Dismantle and descale the showerhead on a set frequency, commonly quarterly, sooner in hard-water areas [4].
- Brush out the individual spray nozzles; replace a head that no longer cleans up.
- Inspect the flexible hose for kinks, sagging and perishing; replace if heavily scaled.
- Encourage tenants to run an unused en-suite or spare shower weekly so it does not stagnate.

**Void recommissioning (before any re-let or after the flat has stood empty)**

- Run the cold supply to displace stagnant water before touching the shower.
- Flush the shower through with the head removed or held low, room ventilated, to avoid generating aerosol.
- Confirm the cold supply runs genuinely cold (below 20°C) at the outlet [2].
- Record the date the property was emptied and the date it was flushed and recommissioned.

**Tenancy handover**

- Walk the new tenant through running a long-unused shower before first proper use.
- Note any second bathroom or rarely-used outlet and put it on a flushing prompt.
- File the current written risk assessment and the cleaning record together so the next void is handled the same way.

## A necessary caveat

This is general guidance to help you think about electric showers, not a risk assessment for your building and not legal or medical advice. The right cleaning frequency, the right controls, and whether your property's risk is genuinely "low" are decisions for a competent person working from a current, site-specific assessment under the ACoP L8 framework. Where a property has stored hot or cold water, vulnerable occupants, or shared communal systems, the simple picture in this article no longer applies and the assessment must reflect that.

## What to do next

Pick one property and write down three facts: when the shower head was last descaled, whether the flat has stood empty in the last month, and whether the cold supply at the shower runs properly cold. If you cannot answer all three, you have just found the gap. The descale and the void flush are small recurring tasks — exactly the kind of thing that slips when it lives in someone's memory and stays under control when the dates are logged and visible. Start with that one property today, then make the same three facts a standing record across the portfolio.

## FAQ

### Can you get Legionnaires' disease from an electric shower?

It is possible but uncommon, and the route is the same as for any shower: inhaling the aerosol the head produces, not the way the water is heated [1]. The electric unit's lack of stored hot water lowers the overall risk, but a head and hose that are scaled, dirty, or full of water that has stood through a void can still spray contaminated droplets. A clean head and a flush after any empty period address the realistic risk.

### Do landlords need a Legionella certificate if the property only has electric showers?

No. There is no such thing as a mandatory Legionella certificate for domestic rentals, and no requirement to hire a consultant for a simple system [3]. What the law requires is that the risk is assessed and controlled. For a flat with mains-fed electric showers and no stored water, that usually means a brief written assessment showing the risk is low, plus sensible cleaning and flushing after voids.

### How often should an electric shower head be descaled?

Your risk assessment sets the exact figure, but cleaning and descaling roughly every three months is the common benchmark, brought forward in hard-water areas where scale forms quickly [4]. The hose deserves the same attention, since it holds standing water between uses. In a soft-water flat in daily use, a clean head and regular running may be the whole regime.

## Related reading

- [Can you catch Legionnaires' disease from your home shower?](https://legionella.io/articles/can-you-catch-legionnaires-disease-from-your-home-shower/)
- [Showerhead cleaning and descaling schedules](https://legionella.io/articles/showerhead-cleaning-and-descaling-schedules/)
- [Landlord responsibilities for Legionella in rental properties](https://legionella.io/articles/landlord-responsibilities-for-legionella-in-rental-properties/)
- [Legionella control in residential rental properties](https://legionella.io/articles/legionella-control-in-residential-rental-properties/)

## Sources

[1] CDC, "How Legionella Spreads". https://www.cdc.gov/legionella/causes/index.html
[2] HSE, "Hot and cold water systems". https://www.hse.gov.uk/legionnaires/hot-and-cold.htm
[3] HSE, "Legionella and landlords' responsibilities". https://www.hse.gov.uk/legionnaires/legionella-landlords-responsibilities.htm
[4] HSE, "Legionnaires' disease: Technical guidance (HSG274)". https://www.hse.gov.uk/pubns/books/hsg274.htm