How to disable a fire sprinkler head

In sprinklered buildings, fire sprinkler heads are installed to discharge water in the event of a fire. They are reliable devices, and sprinkler activations, other than due to a fire or mechanical damage (for example manufacturing defects), are uncommon.

Irresponsible or unplanned isolation of a fire sprinkler head may render the fire sprinkler system inoperable or reduce the effectiveness of the system in the event of a fire and put buildings and lives at risk.

Isolation of a fire sprinkler head in operation

When a fire sprinkler head is in operation (water flows through the open sprinkler), the water being discharged from the operating sprinkler will be flowing from a water supply such as a town main or dedicated sprinkler pumps and tanks. Turning off the water supply will be determined by the Fire and Rescue Service and under no circumstances should anyone else turn the water supply off in the event of a fire.

The relevant fire departments will determine when it might be safe to do so. In the event of mechanical damage, the system water supply must only be isolated by a person who has the authority to do so. In order to remove the sprinkler head, the person performing the task must be trained and competent. Water to the system will be isolated when the installation control valve (sometimes known as a shut off valve, or isolation valve) is closed.

Modification to a system

When alterations are made to a building, it may be necessary to modify the fire sprinkler system to suit the new layout. This may require the isolation of fire sprinklers in order to prevent water damage, minimise accidental discharge, and stop water from flowing. This work should only be carried out by a competent sprinkler contractor.

The design of sprinkler systems is a complex process involving a number of criteria including selection of the correct type of sprinkler head, the correct spacing and location of individual sprinkler heads, the diameter of the pipework, and the location of brackets. In some cases, a full hydraulic calculation may be required. Sprinkler design work can only be carried out by a competent design engineer.

The system may not operate correctly if it has not been designed and installed (or modified) by a competent sprinkler contractor, and any changes may need to be recorded on the system documentation (such as the LPS 1048: Requirements for the approval of sprinkler system contractors in the UK and Ireland Certificate of Conformity, As-Built Drawings and Sprinkler Block Plan).

The system may need to be drained down prior to carrying out the works and may require the isolation of fire alarms and other equipment such as air compressors. The system will need to be refilled, flushed, and tested afterwards. These works should also only be carried out by a competent sprinkler contractor.


Carrying out modification work on a sprinkler installation cannot be undertaken lightly, and a competent sprinkler contractor should be appointed for the task. Works should be planned in advance and should include contingency plans in the event that difficulties may arise.

Prior to any work, the insurer and stakeholders should be notified, and agreement sought from the authorities having jurisdiction. The duration of the works should be kept as short as possible and – if possible – only the affected zones should be isolated.

Alternative fire protection measures

Whilst the sprinkler system is drained down, alternative fire protection measures should be put in place. This may include appointing personnel to keep watch while the system is off, and the use of temporary appliances and extinguishing equipment. These measures may be required out of hours as well as during the normal working day, and at weekend and holidays. Personnel must be competent and fully trained.


The competency of the sprinkler contractor may be demonstrated on third party approval schemes such as those offered by BRE (LPS 1048,, and FIRAS.

The FPA is the UK’s national fire protection association. Find out more about our sprinkler head testing services here.