If your lawn is bermuda grass, it needs about 1” of water per week this time of year while fescue needs about double that or 2” of water per week. This answer usually leads to another question: how long do I run my sprinkler? The answer to that question necessitates you doing what we call a “simple irrigation audit.”

For a simple irrigation audit you are going to need 9 collection cups, a pen, paper, and a calculator (at least most of us will need a calculator). Collection cups can typically be purchased from an irrigation supply store or you can use clean metal cans that might previously have contained tuna, cat food, or perhaps tomato paste. Using the same type of can for all your collection cups will make your data more reliable.

If you choose cans, you can use a ruler and a fine tip permanent marker to mark the outside of the cans in 1/4” increments. Or, you can just measure the collected water by sticking a ruler directly into each collection can.

To collect your measurements, locate your 9 collection cans about 8 feet apart in something close to a 16’ by 16’ grid.

Next, let your sprinkler run over your collection grid for 20 minutes. After the collection period is over, measure the amount of water in each of your collection cups, add up the total amount collected (calculator time), and divide the total by 9 since you were using 9 collection cans. This will give you an average amount of water your collection grid area received in 20 minutes.

So, lets assume your average measured amount was 1/2 inch. This means for every 20 minutes your sprinkler system runs, your turf will be receiving 1/2 of an inch of water. If you have bermuda grass which needs 1” of water per week, you are going to need to water 20 minutes x 2 or 40 minutes per week. You can split this up into two watering sessions per week of 20 minutes each.

If you have a fescue lawn, which needs 2” of water per week, the math says you would need 20 minutes x 4 or 80 minutes per week, which can be split up into two watering sessions of 40 minutes each.

As you can imagine, each zone is going to be a little different, so for complete accuracy you would need to repeat the process for each zone.

Performing this simple irrigation audit will likely end up saving you money as most of us overestimate the water needs of our turf and end up “pouring money down the drain.”