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Comment by jaynos | Hacker News Reader

Sprinkler systems (and the people who don't use them properly) are indeed in need of "automation" as you say. I see so many sprinklers on in the middle of the day (as opposed to early morning, when they should be on) or during a rain storm. It's not that hard to properly set the timer, but people still don't do it.

Get the 80% cases right on sprinklers and the fact that people don't manually override is fine.

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I've never cared for a lawn in my life, so purely out of curiosity, why should a sprinkler system be on in the early morning? Wouldn't morning dew take care of watering grass around those hours?

If you water in the middle of the day, you'll lose more water to evaporation before it can soak into the soil.

A lawn doesn't need a constant mist, it needs a couple of inches of water a couple of times a week. Dew is unlikely to accumulate to that depth. Watering in the morning reduces evaporation.

Morning dew is not enough to consider your lawn watered. Typically you want a few inches of saturated soil for watering.

As for why it's not "ideal" to run sprinklers in the middle of the day, the idea is that if you water early in the morning, then all of your sunlight hours beat on watered grass. If you just started watering in the afternoon, your grass has already been in prime morning sunlight without the watered soil to boost growing. It's not necessarily bad, it's just not ideal.

It's because the rate of evaporation is highest during the noon hours. Water utilities regularly ask people to water their lawns in the early morning or evening to reduce wasting water to evaporation before it can be soaked in by the grass itself.

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