Infrequent, deep lawn watering is superior to frequent, shallow watering (Freshly sodded lawns are a different story).
3 reasons watering short but often is not a good practice.
(1) Watering multiple times a week for a short amount of time does not drive water deep into the soil where it can be absorbed by roots.
(2) It also helps aid in weed germination by keeping the soil moist.
(3) It's also important to let the soil dry out a bit between watering.
Why watering deep is better
So why is it better to water less often but deep?
Deep watering by contrast drives roots deep, making it more drought-tolerant, as they can now access water protected deeper in the soil table.
As water moves through the soil, a vacuum forms that draws air down to the roots where it is needed. The temporary lack of water then forces roots to go even deeper in search of moisture.
How much should I water?
1" of water per week is generally acceptable on established lawns. The best way to gauge this is by setting up some small containers throughout the yard before turning on irrigation system. Start system and also a timer. When the containers have filled with 1" of water, check the timer. That's how long you should *generally* run it once per week (assuming no rainfall).
This will help build a healthier lawn and reduce water wasted to evaporation.
Adjust sprayers as necessary to make sure you're not having too much runoff or watering concrete for no reason. If you need to run the sprinkler for 40 minutes but you start getting runoff at 20 minutes, change zones while the water soaks in, then go back to it for another 20 minutes.
Lastly, make sure you're watering in the early morning or at dusk, with early morning being by far the best method.
We waste millions of gallons of water per year to overwatering lawns. This is a simple way to start saving water and money.
Read more here:
Lawn Mowing Height
Mow your lawn high for healthier turf.
How Often Should You Water Your Lawn?
Infrequent, deep lawn watering is superior to frequent, shallow watering.