Quick answer
Sudden low water pressure in a commercial property is usually caused by a failed booster pump or booster controller, a low cold water storage tank, a closed or failed valve, a leak, or a problem with the incoming supply. If only upper floors are affected, suspect the booster set; if mains-fed ground-floor outlets are also low, check with the water supplier for local outages.
First, map the problem
| Observation | Likely cause |
|---|---|
| Whole street or area affected | Water supplier network |
| Ground floor fine, upper floors low or dry | Booster set failure |
| Booster panel shows alarms | Pump, sensor, drive or low-level protection |
| Storage tank low | Float valve, incoming supply or leak |
| One riser or area affected | Valve, local leak or airlock |
Booster set failures
Booster sets have pumps, a controller, pressure sensors and protection against running dry. If the tank is low, protection may stop the pumps. If the controller or sensor fails, the pumps may not start.
Safe checks
- see whether the booster panel shows alarms (do not open it)
- check whether the cold water tank level indicator, if fitted, is low
- ask whether any work has recently been done on the system
Do not open panels or change pressure settings. Too much pressure can damage fittings and pipework.
Water hygiene
After interruptions and repairs, follow your legionella risk assessment and water hygiene procedures when restoring supply.
See water pressure failures or call 020 7998 9005.
Frequently asked questions
Who is responsible for low water pressure?
The water supplier is responsible for the public network up to the property. Booster sets, tanks and pipework inside the building are the building owner's or occupier's responsibility.
UK guidance and references
Primary and industry sources relevant to this subject. Always check the current edition and how it applies to your building.
- Legionnaires' disease (ACOP L8) Health and Safety Executive
- Water Supply (Water Fittings) Regulations 1999 legislation.gov.uk
This guide is general information for commercial building operators. It does not replace an assessment by a competent engineer. If you smell gas or a CO alarm sounds, leave the area and call 0800 111 999; if there is a risk to life, call 999.