Legionella and little-used taps, showers and outdoor outlets

Most homes have at least one outlet that hardly gets used: a guest shower, a basin in a spare room, an outdoor shower that only runs in summer, or a whole holiday let that sits empty between bookings. Water that sits still in pipes for a long time is a hygiene concern, and legionella bacteria are the reason most often given.

This page explains the idea in general terms and points you to the official guidance. It is not medical advice, and it is not a method for an employer's or a landlord's formal risk assessment.

What legionella is

The Health and Safety Executive (HSE) explains on its page about legionella and landlords' responsibilities that Legionnaires' disease is "a potentially fatal form of pneumonia caused by the inhalation of small droplets of contaminated water containing legionella", and that "all man-made hot and cold water systems are likely to provide an environment where legionella can grow."

The key words are "inhalation of small droplets". HSE's page explains that showers create and disperse water droplets that may be inhaled, which is why showers come up so often in this guidance.

If you are worried about your health or have symptoms, this page cannot help. Read the NHS page on Legionnaires' disease and contact a GP or NHS 111.

Why little-used outlets matter

HSE's simple summary for domestic water systems is to "keep the hot water hot, cold water cold and keep it moving." Little-used outlets break the last part. Water sits in the pipe leading to them, slowly warms or cools towards room temperature, and stops being refreshed.

HSE describes the risk in most homes as generally low, because water is used every day and turns over. Where that stops happening, the picture changes. Common examples:

• Spare bathrooms and en suites that are rarely used.
• Showers in particular, because they make spray. HSE advises that showerheads are cleaned regularly. Our guide to shower heads and hoses covers removing and descaling a head.
• Outdoor outlets, such as an outdoor shower or a garden tap that stands unused over winter.
• Pipes that go nowhere, sometimes called dead legs, left behind after an old basin or appliance was removed. HSE lists making sure redundant pipework is removed as one simple control.
• Stored water. A loft cold water tank should have a tight-fitting lid, which HSE mentions, and a hot water cylinder should be kept at the temperature its installer set.
• Empty properties, such as holiday lets, second homes or a house left empty for a long time.

What HSE says about outlets that are not used

HSE's landlord page says that "as a general principle, outlets on hot and cold water systems should be used at least once a week to maintain a degree of water flow and minimise the chances of stagnation." That sentence is HSE's, written for properties left vacant; we have not added to it.

For properties left empty for long periods, the same page says "consideration should be given to implementing a suitable flushing regime or other measures such as draining the system". It does not give a single method for every home, and neither do we. If you look after an empty property or a holiday let, read HSE's guidance in full and get advice from a plumber or a water hygiene specialist if you are unsure.

Landlords and holiday lets

HSE explains that landlords have legal duties to assess and control the risk from legionella for their tenants. It says that in most homes this "does not require an in-depth, detailed assessment", and that "health and safety law does not require landlords to obtain or produce a 'legionella test certificate'". It also says many landlords can assess the risk themselves.

We do not summarise all of a landlord's duties here, and this is not legal advice. Read the HSE page and its links. If you rent, our guide to tenant vs landlord plumbing repairs covers who usually deals with what, and HSE says tenants should tell the landlord if the hot water is not heating properly or there are other problems with the system.

Employers and others in control of premises have their own duties under HSE's approved code of practice. This page is not a guide to that.

Practical, low-risk habits at home

Without going beyond what the official sources say, a few habits make sense:

• Use the outlets you have. Run little-used taps and showers from time to time, rather than leaving them for months.
• Keep shower heads clean. Limescale and grime in a head or hose are worth dealing with.
• Remove what is not needed. If a basin, outside tap or shower has been taken out, ask a plumber to remove the pipe that fed it rather than just capping it at the outlet.
• Leave the hot water settings to the installer. Do not turn a cylinder thermostat down without asking the person who set it.
• Plan for long absences. If a home will be empty for a long time, think about it before you leave and ask a plumber how best to manage the system.

A pumped hot water loop keeps water moving in some larger homes; see secondary hot water returns.

Is legionella a problem in ordinary homes?

HSE describes the risk in most residential settings as generally low, because water is used and turned over every day. Little-used outlets and empty properties are where it deserves more thought.

Should I get my home tested for legionella?

HSE says testing is not usually required for domestic hot and cold water systems and is only needed in very specific circumstances. If you are a landlord or have a particular concern, read HSE's guidance.

I feel unwell after using a shower that had not been used for a while. What should I do?

This page is not medical advice. Read the NHS page on Legionnaires' disease and contact a GP or NHS 111 for advice.