Fire sprinkler leaking? What causes it and how it gets fixed

A fire sprinkler leaking in your building usually shows up in one of three places: a sprinkler head that drips, a wet spot under a pipe joint, or water around the valves in the riser room. It is something we find and repair regularly on wet, dry and pre-action systems. This is where leaks come from, what the code says about a leaking head, and who to call to get it fixed.

Where sprinkler leaks come from

Most of the leaks we find on sprinkler systems start in one of these places:

• Sprinkler heads. Water dripping from the head itself.
• Pipe and fittings. Water at a joint, a coupling or a fitting along the pipe.
• Valves in the riser room. A valve that does not seal fully when it is closed, or a test or drain valve that drips.
• Low-point drains. The small drains at the low points of a dry or pre-action system.

On a dry or pre-action system the pipes are filled with air or nitrogen rather than water, so a leak can also show up as a compressor that keeps running instead of as a drip — that is covered on our page about air and nitrogen leaks on a pre-action sprinkler system. A leak at the backflow preventer is a separate job, handled under backflow preventer repair.

What causes leaks in fire sprinkler piping

Corrosion inside the pipe is a common cause. Research by the property insurer FM Global found that corrosion occurs in every type of sprinkler system — wet, dry and pre-action — and that corrosion leaks can come from several causes, alone or together. Here are three of them:

• Air trapped in a wet system. A wet system's pipes are kept full of water, and corrosion forms near any pockets of air left inside.
• Water left in a dry system. A dry system's pipes are meant to hold air, not water. Water left standing in them corrodes the pipe from the inside.
• The water itself. Treated city water causes less corrosion than untreated water, and fresh water added during maintenance brings oxygen into the pipe.

What builds up inside the pipe does not show on the outside, which is why sprinkler systems get a five-year internal sprinkler inspection that opens the pipe and looks inside. The same research points to ways of slowing corrosion: nitrogen in place of compressed air on dry and pre-action systems, a vent that lets trapped air out of a wet system, and treated water as the supply.

What the code says about a leaking fire sprinkler head

NFPA 25, the code sprinkler systems are inspected and maintained to, says any sprinkler head that shows signs of leakage is replaced. The same goes for a head that has been physically damaged, or one whose glass bulb has lost its liquid. Corrosion or a build-up of dust and debris on a head can lead to replacement too.

What to do when you find a leak

Call your fire sprinkler contractor and tell them where the water is coming from — a head, a pipe or a valve — and how much of it there is.

Whether any part of the system should be shut off while the repair is arranged is a decision to make with us when you call. A valve closed to stop a leak has to be reopened once the repair is done, which is why valve position is checked at every inspection. Our article on a closed sprinkler control valve explains more.

How inspection finds leaks

On a wet system, sprinklers and piping get a floor-level visual inspection once a year, and the code says the pipe and fittings should be free of leaks, damage and corrosion. Many of the leaks we write up are ones you would not notice day to day — a valve in the riser room that does not close tight, or a small drain that drips.

If a sprinkler head or pipe in your building is dripping, or your last inspection report lists a leak that has not been repaired yet, tell us where it is and what you are seeing. Our fire sprinkler repair work covers heads, pipe, fittings and valves on wet, dry and pre-action systems across New Jersey, Pennsylvania and Delaware, and our emergency line is answered around the clock.