Doing a Simple “Tuna Can” Sprinkler Audit … IS THE WAY TO GO!

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So, when was the last time you made sure that your lawn sprinkler system is programmed and watering as accurately as you think it is?

… Especially if you’re seeing brown grass in your lawn?

In this article, we’ll go more in-depth, beyond our previous blog article, “Irrigation, droughts – and strange weather … HOT, DRY SUMMER TURF TIPS from Red Hen Turf Farm“, so be sure to check that one out, too! This previous article explains, for one thing, that an established cool season grass lawn in our part of the country (northwest Indiana / midwest) will need 1 to 1.5 inches of irrigation each week depending on weather, soil type, slope, etc.

But how can you really know that you’re sprinkler system is programmed with this goal in mind?

TIP: If you’re reading this and you’re NOT in the Northwest Indiana area, check with your local Cooperative Extension Service office for precise weekly watering recommendations.

Here’s something many people find surprising… When rains are not part of that irrigation, you’re never going to get as good results as Mother Nature. Natural rainfall reduces the need for SUPPLEMENTAL IRRIGATION, but irrigation is always just that – SUPPLEMENTAL. When considering how long to run your sprinklers, you’ll want to adjust to account for rainfall. A good old-fashioned rain gauge will come in handy for this. To figure out how long to water your lawn during a week when it rains, subtract the number of inches of rainfall from the weekly watering need to get your new weekly watering figure and do the rest of the calculations we’ll be describing below normally.

In “Irrigation, droughts – and strange weather … HOT, DRY SUMMER TURF TIPS from Red Hen Turf Farm“, we went into in a good amount of detail on how you have a few options on how to approach watering your lawn during a hot, dry, doughty period, and how it makes a difference whether you’re dealing with a fully established lawn or sod / seed that is new or has been in your yard for less for than a year. We’d also recommend checking out the experts at Purdue’s excellent guide, “Irrigation Practices for Homelawns,” HERE

Beyond the information to come below, both Red Hen’s article and Purdue’s Irrigation Guide discuss how the time of day you’re watering, slopes, soil compaction, new seedings / new sod, the choice of letting your lawn go dormant, and more should also be considered.

It’s near the end of August of 2020 now, and here in northwest Indiana, we’ve had a very hot and dry summer, which is stressful on any fully established yard, but when it comes to newly laid sod, it can be quite the task to do all you can to water your sod when it’s trying to re-establish it’s root system in its new home.

Based on the calls, texts, and photos we have been receiving during the hottest, driest, parts of the summer from concerned customers, probably 90-95% of the lawn problems and brown / yellow spots are caused by lack of water, and so often it comes down to a sprinkler system / irrigation issue.

LEFT: Turf has been irrigated during a drought. RIGHT: Turf turning dormant.

Though you might water for the amount of time your sprinkler system has been programmed for… say it’s 30-40 minutes, and you feel it should be “enough,” maybe you’re seeing brown or yellow spots. If this is happening, do you know how many inches of water each individual sprinkler head is putting down?

In other words, have you checked your sprinkler system and/or performed a “Sprinkler Audit” or “Irrigation Audit” or what we sometimes call the “Tuna Can Test”?

Surprisingly (and frustratingly) even a new sprinkler system can have heads that are not operating as you’d want them to!

The thing is… it’s impossible to determine the distribution of water by looking at your sprinkler system while it’s running. It will look fine unless you test it out more methodically.

That’s where a simple Irrigation / Sprinkler Audit can help bring any issues to light.

OUR PREDICTED MAIN TAKEAWAY once you complete your Sprinkler Audit: After following the steps to do an Irrigation Audit, you’re likely to discover that the areas that are browning are probably being skipped by irrigation, or not getting enough water. Adjustments you make will likely take 2-3 weeks to make an observable difference in your lawn, especially with Kentucky Bluegrass. Red Hen’s Rhizomatous Tall Fescue Sod will likely bounce back quicker than our Bluegrass Sod (HERE’s MORE on the main differences between our 2 types of sod)

Here are the basic steps for a Simple Sprinkler Audit / Tuna Can Test:

  1. Put out 10 to 12 containers of the same size in a zone, placing them in both in the green areas and the brown/dying areas. Tuna cans or plastic cups work great!
  2. Run your irrigation system for a set period of time. For instance, 10 minutes, or 1/6th of an hour, would be a good amount of time for this Sprinkler Audit.
  3. At the set period of time, promptly turn the heads off, and take some time to get down and really look at your sprinkler heads…
    • Is each one popping up out of the ground, perpendicular to the ground?
    • Is each head functioning properly?
    • Any heads that are not popping up fully or are tilted will lead to non-uniform distribution of water.
    • If you’re watering around curves, it is probably going to take some adjusting so that all areas are covered.
  4. Now, look at how much water is in each of the cups.
    • Are there any vast differences of the amount of water collected in the cups? If so, go back to that area with the sprinkler heads and take another close look.
    • Are you noticing a correlation between a head that is not functioning properly and the limited water output?
  5. Now measure how many inches of water the cups are showing that you’re putting out during this time period.
    • Let’s say for this test, you have applied 1/4 inch of water in 10 minutes. Based on this output, if you were to run your system for 30 minutes), then 1/4 inch X 3 (since 10 minutes X 3 = 30 minutes) means you’d be putting down .75 inch of water per each 30 minutes of running your sprinkler system. To get 1.5 inches per week, for this example, you’d need to run it twice a week for 30 minutes.
    • As stated above, right now, between rain water and irrigation, most lawns will need about 1 to 1.5 inches of water/week if you want to keep it greened up (versus letting it go dormant).
    • Even if you choose to let your lawn to dormant, you’d need 1/2 inch of water every two weeks just to maintain hydration to the grass plants’ crowns. (Again, refer to THIS RED HEN ARTICLE for more details on different approaches to watering during hot, dry periods)
  6. Start again with step 1 for any other zones you have that you’d like to test out.
  7. REPEAT OFTEN???!!!! It’s a good idea to do this type of Sprinkler Audit at least once a year, and more often if you’re noticing possible issues such as mysterious brown / dying areas. Even if you’re sprinkler system is new, it’s a good idea to test it out.
Sprinkler Audit Math Example

Remember that this Sprinkler Audit is showing you the results of one single application of water. If your cups are not equally – or uniformly – filled, this means that over a period of months or years, some parts of your lawn may be getting twice as much (or three times as much) water as others. This can add up to 10 inches annually versus 20 inches, or 10 inches versus 30 inches. A difference as small as 1/4 inch during each irrigation cycle can add up to dozens of inches per year.

Even if you’re running your sprinkler system twice per week for … say… 30 minutes because that’s what you feel should be right, it may not be enough water. Take into account that the type of your sprinkler head affects how much water is being put out during your 30 minute rounds. Generally, rotor heads will take a longer time to put irrigation out, so depending how how much water your Sprinkler Audit shows you’re putting out, you may have to run these for three times per week to achieve the desired inches of watering per cycle.

Besides determining how uniform your sprinkler system heads are putting out water, and the output levels, other factors to consider when facing browning grass in the midst of an especially hot, dry summer include, but are not limited to:

  1. Areas of your lawn in full sun versus shade tend to need more watering
  2. Areas exposed to extra heat coming from nearby sidewalks, concrete, stonework, or perhaps even a white or light-colored fence that is reflecting sunlight / radiant heat onto your grass can make a bigger difference that you’d think, so if you’re seeing browning in these areas, you’ll need to adjust for more water.
  3. Hilltops tend to dry out faster than lower areas, so they will need more water.

When comparing Red Hen’s 2 types of sod, Kentucky bluegrass may take 2-3 weeks to recoup and start turning green again. On the other hand, tall fescue will tend to bounce back quicker from a droughty period.

If any questions come to mind after reading this article and the links we’ve included, let us know!

To chat by phone with one of Red Hen Turf Farm’s knowledgeable customer service team members, the number to call is 574-232-6811. (Our Business Hours are HERE)

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