Sprinklers before the first frost, and the pipework in the cold spaces

On 26 November 2020 the sprinkler threshold for new blocks of flats in England dropped from 30 metres to 11 metres. Since then, almost every new block of four storeys or more built to the guidance in Approved Document B has gone up with a sprinkler system, usually to BS 9251, and in mixed-use and commercial parts often to BS EN 12845.

So a lot of residential managers now look after a system they did not have five years ago. Most of it sits inside heated flats and corridors, where it is not much trouble in winter. The parts that cause trouble are the ones in the cold.

Where the cold gets in

A wet sprinkler system is full of water all the way to the heads. If any part of it freezes, two things can go wrong. The ice blocks the pipe, so that section will not deliver water in a fire, and the expansion can split a fitting or a pipe, so when it thaws the system floods whatever is underneath.

In a typical block the vulnerable places are predictable:

• The tank and pump room. Often at basement or ground level, sometimes in an outbuilding. The Fire Protection Association's guidance, drawing on the LPC Sprinkler Rules, says a pumphouse with electric pumps should be kept at 4°C or above, and one with diesel pumps at 10°C or above.
• The car park. Open or naturally ventilated car parks are cold for months. Car park sprinklers are normally designed to BS EN 12845 and are often dry or protected with trace heating for exactly this reason.
• Bin stores, cycle stores and plant rooms with louvres to the outside.
• Pipework through roof voids, soffits and external walls, especially where a refit has moved insulation.
• Drain valves, test lines and small trim pipework, which hold standing water and are easy to forget.

What the checks look like

The FPA's winter guidance is a good working list, and most of it is cheap:

• Check that heating in the pump room and the valve enclosure is automatic, working, and set to the right temperature. Check that louvres open and close and are not jammed.
• Where pipework is trace heated, check it is working. The LPC technical bulletin TB 203 asks for a weekly check, with the adequacy of frost protection reviewed quarterly and at least once a year by an independent third party.
• Look at the lagging. Insulation slows freezing but does not stop it in a long cold spell, and damaged or wet lagging does very little.
• Test any tank immersion heater, and make sure the tank ball valve and inlet are protected.
• Drain the pump test return line and any exposed drain valves so they cannot hold water.
• If the system has alternate wet and dry sections, which are changed over to air in autumn, book the changeover now. The Sprinkler Rules no longer allow alternate systems in new installations, but older ones are still in service.

None of this replaces the routine servicing to the relevant standard. It sits alongside it, and it is seasonal, which is why it tends to be the first thing missed.

Where it usually goes wrong

The annual service is normally in hand, because a contractor owns the date. The frost checks are not. They fall between the sprinkler contractor, the M&E contractor who looks after the heating and the site team who walk the building, and in many blocks nobody has written down whose job they are.

The other gap is records. If a pipe splits in January, the insurer and the fire risk assessor will both want to see what was checked before the cold arrived, when, and by whom. "The heating was on" is not a record.

What to do this month

Before the first hard frost, walk the system from the tank and pumps outwards and list every part of it that sits in an unheated space. For each one, note the frost protection, whether that is heating, trace heating, lagging or a dry section, and who checks it. Put the weekly and quarterly checks on a calendar with a named owner. And make sure the last service report and any outstanding remedials are filed with the building, not only with the contractor.

Where SAMRISK puts it

SAMRISK holds the building and the land it sits on across thirty connected systems, twenty for the building and ten for the land.

The sprinkler installation is held in the fire safety register, with the tank, pumps, valve sets and trace heating circuits recorded as items against the building and marked on the building plans, so a cold spot has a location. The weekly, quarterly and annual frost checks sit on the compliance calendar alongside the routine service, each with an owner and a pass or fail history. A failed heater or damaged lagging raises a maintenance job, the sprinkler and M&E contractors are recorded through contractors and permits, and their reports are filed in documents.

Sources: GOV.UK, Approved Document B May 2020 amendment, circular letter, threshold for sprinklers in new blocks of flats reduced from 30m to 11m with effect from 26 November 2020; Fire Protection Association, how to winterise your fire sprinkler system, citing BS EN 12845:2015+A1:2019 clause 20 and the LPC Rules for Automatic Sprinkler Installations 2015 incorporating TB 203; BS 9251:2021 Fire sprinkler systems for domestic and residential occupancies.