Frozen water in the system can cause damage to the equipment, including the fire pumps, sprinkler tanks, valves, pipework, fittings and sprinkler heads - and may cause the system to become inoperable.

Arrangements should be made to check that there is no danger of freezing to any part of the sprinkler system. This may be reasonably clear to establish in areas such as external loading canopies or unheated loading docks and stores, but may not be as apparent in areas such as (but not limited to):

  • buildings normally heated but not heated, for example over shutdown periods or holidays
  • unheated ceiling voids
  • sprinklers adjacent to openings, such as delivery doors and hatches or louvres

Maintenance of sprinkler systems

It is vital that sprinkler systems are maintained and tested throughout the year - not just during the summer months but also during the winter. It is important to plan ahead, as inclement weather causing ice and snow may make access to the site more difficult, with conditions such as ice hindering deliveries and maintenance.

Some simple measures such as providing grit (salt) may be helpful in keeping access routes clear.

Sprinkler systems must continue to be maintained at all times in accordance with BS EN 12845: 2015 + A1: 2019 Fixed firefighting systems. Automatic sprinkler systems. Design, installation and maintenance(specifically clause 20), and the LPC Rules for Automatic Sprinkler Installations 2015 (the Sprinkler Rules), incorporating BS EN 12845’s technical bulletin TB 203.

Types of sprinkler system

The main types of sprinkler system are:

Wet pipe systems - permanently charged with water at all times

Dry pipe systems - charged with compressed air - In the event of operation, the air is forced out of the pipework by sprinkler water under pressure

Alternate wet and dry pipe systems -charged with water during the summer months and compressed air during the winter months,in the UK they are changed over from air to water in the spring, and from water to air during the autumn (the Sprinkler Rules no longer permit the use of alternate wet and dry systems in new installations, although there are many of these types of systems in existing use, and there is no requirement to replace them)

Pre action systems - normally charged with air and operated in conjunction with a detection system

Tail end systems (or subsidiary pipe systems) - extensions to wet pipe systems, these are normally used in places such as loading canopies or unheated loading docks.

Trace heating systems - trace heating and lagging is applied to sprinkler pipework where there is a possibility of freezing (such as loading canopies), and where trace heating has been installed, this should be checked and serviced by a specialist contractor -it is important to check that trace heating is working, and this should be checked on a weekly basis as required by the Sprinkler Rules technical bulletin TB (also refer to the Sprinkler Rules Part 3, RC38 Recommendations for Frost protection measures for sprinklers). It is also a requirement of TB203.3.2.3 that the adequacy of the frost protection measures should be checked quarterly as part of a review of hazard, and at least once per year, this should be conducted by an independent third party, such as the Fire Protection Association. Find out more about our independent sprinkler inspection service

Duplication of trace heating elements

There should be duplicate elements to protect the pipework from freezing.

Each circuit should be separately monitored, and the systems should be checked to see that the signals are working correctly.

As with all electrical circuits, precautions must be taken to avoid overheating and prevent fire. All electrical components should be checked by suitably qualified electricians, including electrical overload devices and residual current devices (RCD).


Where sprinkler pipework has been lagged, the condition of the lagging should be checked and replaced where damaged or worn. Lagging should meet Euroclass requirements, and specialist suppliers should be used.


Check that enclosures containing sprinkler equipment such as pumps and installation control valve sets have been fitted with adequate heating. Heating should be automatic, and thermostats should be checked for correct operation alongside whether they are set to the correct temperatures.

If there are louvres, these should be suitable. Check that automatic louvers operate correctly and have not become locked in the open or closed position.

Sprinkler pumphouse

Where the system is served by fire pumps, the sprinkler pumphouse must be maintained at the correct temperature at all times. Pumphouse heating must be maintained at a temperature of at least 4° C for pumphouses containing electric motor driven pumps, and at least 10°C for pumphouses containing diesel engine driven pumps.


The ball valves on the sprinkler tank must not be allowed to freeze. This is normally achieved by a special immersion heater installed by the tank manufacturer, which ensures that water around the ball valves does not freeze. Tank Immersion heaters should be tested.

Check that the water supply pipework into the tank and the suction pipework from the tank are adequately protected by trace heating and lagging.

Check that the pump test return pipework has been drained and cannot freeze. Pressure tanks and houses should be maintained at 4°C or above.

Tank infill pipe flow meter

Where a flow meter is installed on the incoming infill pipe (for verifying the flow rate into the tank), trapped sections of trim pipework should be drained, and the manufacturer’s recommendations should be followed.

Drain valve on sprinkler tank

If exposed to freezing conditions, this should be protected against freezing and should be lagged and if necessary trace heated.

Fuel supplies to diesel pumps

Where the pumps are diesel engine driven, ensure sufficient diesel fuel is available at all times. Consideration should be given to delivery and storage of diesel fuel. Access to the pumphouse must be maintained. Routes should be cleared and gritted.


Ensure there is an adequate supply of spares. Stocks should be available at all times.


The building owner/occupier should review the potential consequences of severe weather which may continue for several months.

This should include planning for carrying out routine weekly testing as well as planned maintenance procedures.

Where weekly tests are carried out in house, arrangements should be made to ensure staff are able to attend the premises, and consideration should be given to training more than one person to perform these tasks. It is important to make sure the system is tested and maintained regularly as required in the Sprinkler Rules.

Inclement weather

When testing, water is normally discharged into drains. These drains should be cleared so that water does not spill over and potentially form icy surfaces.

Where water is discharged on to surfaces such as hardstanding, this should only be carried out when safe to do so, and arrangements should be made to avoid the build up of ice and slippery surfaces.

Dry, alternate, pre action and tail end air valve compressors

Ensure the compressors have been serviced and are in good condition, as the systems may be “on air” for several months over the winter period (or permanently if the system is a dry pipe system).

Complete drainage

Before winter, wet pipe , alternate wet and dry pipe and tail end air systems must be thoroughly drained to ensure there is no water trapped in the pipework. Pipework should be checked for signs of damage. Where for example the brackets have been damaged and the pipework no longer has the drainage slopes required in the Sprinkler Rules, water may become trapped and therefore be subject to freezing.

Below ground pipework

Below ground pipework should be at least 750mm below the surface.

Find more sprinkler system maintenance and testing guidance here.

Please be aware that considerable efforts have been made to ensure the accuracy of the information contained within this article at the time of publication, however any legislative (or other) changes that come into effect after this may render the information out of date until it is reviewed and updated as part of the FPA’s content review cycle.