Why did my sprinkler pipes crack over the winter?

Freezing water did it. When water is left inside your sprinkler lines, valves or backflow device, it freezes and expands. That pressure can split or crack pipes, even those buried underground.^[1] Rain Bird says the same thing in plain terms: if any water freezes in your sprinkler pipes, it will expand, which can cause them to break or burst.^[4]

Why buried pipes are not safe

Many people assume sprinkler pipes sit below the frost line. Richmond Public Utilities warns that in most yards, sprinkler lines are not buried deep enough to be protected from the cold.^[1] Sprinkler pipe is laid shallow, so a hard freeze reaches it.

The damage depends on where the water sat. Richmond's guidance is blunt: water left inside pipes is the main cause of winter damage.^[1] The usual culprits are a zone that was never fully drained, a low spot in the pipe run where water collects, a valve that still held water, and a backflow device left uncovered above ground.

Sometimes the system was never drained at all, and sometimes a drain valve was stuck or an air blow-out missed a section. Either way, you find out in spring.

Finding the damage in spring

Winter does not leave a clear signal. Rain Bird puts it this way: pipes may have frozen, seals may have cracked, and your backflow preventer may need close inspection.^[2] A quiet crack can run for weeks before you see it, which is why Richmond lists higher water bills from unnoticed damage as one result of failing to winterize.^[1]

Start at the backflow device. Look for visible cracks or damage from the winter freeze.^[2] Then bring the water back slowly. Rain Bird advises opening the valve slowly and gradually to pressurize the system to avoid unnecessary wear and tear.^[2] Opening it fast can turn a hairline crack into a blowout.

Run each zone for a minute or two and walk it. Water pooling at a head or along a line, a head that mists, or a zone with weak pressure points to a split pipe or a cracked fitting. If you want the full spring routine, see how to turn a sprinkler system back on in spring.

One caution: high pressure causes similar damage on its own. Rain Bird notes that a system with too much pressure will result in cracked pipes, busted valves, sprinkler head leaks and inefficient watering.^[3] If a pipe cracked in a mild winter, pressure may be part of the story.

What a repair involves

A cracked head or riser near the surface is a small job; see how to replace a broken sprinkler head. A split in buried pipe means digging, cutting out the damaged section and splicing in new pipe and fittings, and it may mean several breaks in one zone, because ice rarely cracks only one spot. A cracked valve or backflow device is a different matter again. For cost drivers, see what a sprinkler repair costs in Virginia.

Stop and call a pro if

• Water keeps running after you close the mainline valve. That points to a valve or a leak on the house side of the system.
• The backflow device is cracked. It protects the drinking water, and ask your water utility who may test and replace it; see what a backflow preventer is and how it is tested.
• You find more than one wet spot in a zone. Several breaks mean a longer repair, and a contractor can pressure-test each section.
• The leak is near the house, driveway or a utility line. Do not dig there yourself.
• The water bill jumped and you cannot find a wet spot. A hidden leak needs a professional.

Preventing a repeat

Drain the system before the first hard freeze, every fall. How to winterize a sprinkler system walks through the options, and when to winterize in Virginia covers timing. If you would rather pay for it, read whether to hire someone to blow out your lines. Browse more irrigation answers or irrigation businesses.

When you are ready, describe the sprinkler damage once and licensed local contractors can quote it.