Smarter Garden Watering: How To Measure And Manage Outdoor Water Use

The sprinkler comes on at 7 in the evening and goes off at 7:20. It has been 20 minutes for 3 years. Somebody set it that way the first summer, nothing obviously died, and so 20 minutes became the rule of the house, and what none of them can tell you is what 20 minutes puts on the grass, which could be a quarter of an inch or could be an inch and a half.

That gap can strongly influence whether the grass sends roots 6 inches down or keeps all of them in the top couple of inches, sitting there waiting to fry in August. So the lawn is being watered on a guess that got repeated until it started to look like a schedule.

Which means the useful question was never how long to run the thing. It is how much comes out of it while it runs, and a handful of empty tuna cans will tell you inside 15 minutes.

How Much Water A Lawn Needs In A Week

Many established lawns need roughly 1 to 1.5 inches a week during active growth, including rainfall, though actual demand shifts with grass type, soil and weather. Colorado State reckons a lawn in a hot, dry spell can climb to 2 or 2.25 inches. Drought tolerant grasses sit well under it. And 2 days of decent rain in a week usually means the timer should have been left alone that week.

Usually 1 to 3 deeper irrigations are preferable to daily light watering, provided the soil can take the water without runoff. Water that soaks in properly gives roots a reason to chase it further down. That said, watering alone does not dictate root depth, oxygen does, so does compaction, so does the species you are standing on. Deeper rooted turf copes better between waterings. Shallow rooted turf wilts sooner, the owner reaches for the timer, and the whole thing stays shallow.

An inch across 1,000 square feet is about 623 gallons, and that is the number to keep, because it turns a vague target into something a hose can be held against.

How To Measure Your Sprinkler Or Hose Output

Two methods, neither one eats half an hour. For a sprinkler:

• Scatter at least 6 identical straight sided cans over the watering pattern, a few close to the heads, a few stranded midway between them.
• Run the zone for 15 minutes.
• Measure the water in each can with a ruler and average the readings.
• Multiply that average by 4, which gives you the output in inches per hour.

A quarter of an inch in 15 minutes means the zone throws an inch an hour, so your inch a week is one 30 minute soak twice a week, not 20 minutes every night since March. Once you have the hourly figure for a zone, the run time falls out of it:

Most residential spray zones land between 1 and 2 inches an hour, and rotor zones nearer 0.5 to 1, so a reading of 0.6 on a rotor zone is normal and the same reading on a spray zone means a head or the pressure is off.

The hose is easier. Using a 1 gallon bucket, divide 60 by the number of seconds it takes to fill. Fills in 20 seconds, you are running 3 gallons a minute. A flow meter does that same sum all day instead of once, and a water flow meter sat between tap and hose counts the gallons or liters going past. It pays off on a drip or soaker line more than a sprinkler, since emitters dribble so slowly that a can test on them is an afternoon gone.

The cans do a second job while they sit there. They show you how evenly the zone covers. Half an inch in one and an eighth in the next is not the clock playing up. The distribution is wrong, and no amount of adjusting the controller will fix that.

Why Two Zones On One Timer Deliver Different Amounts

Two zones on one controller, same 20 minutes each, routinely hand out wildly different amounts. Pressure bleeds off along the line. Heads sit at whatever spacing the installer chose. Spray overlap changes from one corner of a yard to another. One zone might throw 1.2 inches an hour while its neighbor manages 0.6, so a single runtime drowns the first and shortchanges the second, every cycle, right through the season. That is the argument for testing each zone on its own rather than testing one and assuming the rest behave like it.

Does it want repeating? Not every few weeks. Redo it when coverage changes, and fold it into maintenance now and then. Numbers slide without anybody touching a wrench. Nozzles silt up, a head settles an inch into soft ground, pressure shifts, a shrub fattens up and starts blocking half the arc.

How To Spot A Broken Head Or A Slow Leak

One cracked head drowns its own patch and abandons another 4 feet away. The instinct is to give the dry patch more minutes, which floods the wet one harder. A head clipped by a mower will water the driveway all summer, and none of those 623 gallons a week is reaching a root. Walking the zone while it runs, once in spring and once in midsummer, catches all of this in about 10 minutes.

A split hose, or a valve that no longer seats, can run for weeks without anyone noticing, because the yard still looks watered, and you find out on a bill 6 weeks later. A meter reading taken with the whole system off settles it. If the number is moving while nothing is running, water is going somewhere it should not be going.

When To Water, And What Mulch Changes

Water put down in the early morning goes onto cool ground with little wind about. Less burns off before it reaches soil, and the blades dry out over the day. Colorado State marks the efficient stretch as roughly 9 at night to 9 in the morning, evaporation being low through the dark hours, and early morning sits at the good end of that because the canopy then gets the daylight to dry. Leaves left wet a long time can encourage some diseases, which is the standard case against late watering, though an evening soak is not automatically a mistake. Midday is generally the least efficient time for overhead watering, between evaporation and wind.

What Mulch Does To The Number

Mulch holds moisture in the soil rather than letting it lift off the surface, and it is the one change in this article that can be measured with the same cans and bucket. Run the bucket test on the bed’s soaker line before the mulch goes down and note the minutes per run, then lay 2 to 3 inches of bark over the bed and watch the interval, because a bed that needed a soak every 3 days in July is usually stretching to 5 or 6 under mulch, and if it is not stretching, the mulch is too thin or the emitters are sitting on top of it instead of under it. Grouping plants by how much they drink does the same job on a smaller scale, since a bed of thirsty and drought tolerant plants on one line is being watered for the thirstiest and drowning the rest. Drip lines put the water at the root and skip the leaf, so the morning versus evening question largely stops mattering on a dripped bed.

The change to make this week, since it is late September, is the first cut of the year on the controller. Growth is slowing, the week’s need is dropping from 1.5 inches toward 1, and the 2 soaks a week that carried July are now 1 soak, or 2 shorter ones, at whatever your can test said the zone puts out. Pencil the inches per hour for each zone inside the controller door when you do it, so that next April the number is there and the 20 minute guess does not come back.