Irrigation: watering the lawn without watering the house

Restoration Pros have a name for the wet basement, the rotten window sill and the peeling paint on the one wall that is always failing: the sprinkler wall. An irrigation system runs at five in the morning when nobody is watching, and a head that has turned toward the house, or a schedule that never changed since it was installed, delivers hundreds of gallons of water a week to exactly the wrong place.

Walk it while it runs

Once a month in the season, run each zone during daylight and walk it. You are looking for:

• Heads spraying the house, the windows, the foundation, the fence or the driveway. Adjust the arc or the nozzle, or move the head. Every bit of water that lands on the house is water the house has to shed.
• Heads that do not pop up, are stuck up, are broken off, or spray a mist instead of a stream. A mist means the pressure is too high; a regulator fixes it and saves a great deal of water.
• Puddles, especially near the house. A puddle at a head after the zone shuts off is a valve that is not closing or a broken lateral line leaking underground.
• Water running down the sidewalk and the street. That is a schedule running longer than the soil can take in.

The schedule

Most lawns need about an inch of water a week, including rain, delivered in two or three deep soakings rather than every day. Daily short watering grows shallow roots and fungus. Water in the early morning, before the wind and the sun; evening watering leaves the grass wet overnight, which is how lawn disease spreads.

A controller with a rain sensor or a weather-based smart controller adjusts on its own and pays for itself in one summer. The alternative is a person who remembers to change the settings in July and again in September, and that person is rare.

The backflow preventer

The device where the irrigation line leaves the house plumbing keeps fertilizer, pesticides and standing water from being drawn back into the drinking water if the pressure drops. Most cities require it, and many require a yearly test by a certified tester. If yours is above ground, it has to be protected from freezing in winter and from the mower all summer. If you do not know whether you have one, a plumber or an irrigation Pro can tell you in a minute, and adding one is not optional.

Beds and drip

Sprinkler heads in a shrub bed water the leaves and the mulch and miss the roots. Drip lines under the mulch put the water where the plant is, use a fraction of the volume, and keep the foundation dry. Converting a bed zone from spray to drip is a morning's work.

Fall and spring

Blow the system out with compressed air before the first freeze in cold climates; a line that freezes full of water splits, and the break shows up as a wet spot in May. In spring, open the valve slowly, check the backflow device, and walk every zone before setting the schedule.

When the wall is already wet

If one wall of the house has peeling paint, soft trim or a damp basement corner, look at the sprinklers before anything else. Fix the heads, then let the wall dry for a few weeks, then see whether the problem was ever anything but the water.