Watering too long

I have 13 zones with 4 heads in each zone. I am operating on a well so it has a 6 gallon a minute return. I have 1.5 gallon per minute nozzels on my sprinklers. According to Rainbird that equates to .27 in/hr preceipitation rate. I plug everything in to Rachio and it says 18 hrs a day watering. That is way too much. What should I do?

If the output of each zone is really .27 inches per hour, and each zone was watering for almost an hour and a half, then your total run time would be 18 hours. Each zone would only be getting .37 inches of water per cycle though (assuming each cycle runs for 1.38 hours, a total of 18 hours between 13 zones).


I know. That’s why it waters every day.

.27in/hr seems really really low unless that’s a drip line. Water pressure also affects output. You can either use our defaults (and then adjust from there) or do a catch cup test to get the exact precip rate.


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Yes that’s only a few hundredths of an inch away from my driplines (.22-.24 in/hr). The Rain bird calculated precipitation rate doesn’t pass the reasonableness test for lawn sprinklers. Catch cup test is the best way to go, definite need to verify that precip rate.

I put it at default which is an inch per hour. I will have to put the catch cup out and let it run.

Ok I did a catch cup test. I put out 10 cups spaced them out evenly. This was zone 2. I ran it for 20 minutes. Then ran zone 3 for 20 minutes. This one overlaps some. Then looked at all the numbers. I averaged the 10 cups then multiplied by 3 to get my inches per hour. The total was .21. That is crazy low.

My sprinkler heads are 1.5 gallon nozzles. I have 4 heads in a zone. My well is only a 6 gallon a minute return. So I shouldn’t go over that correct?

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Those numbers are plausible.

If you deposit 6 GPM for 20 min. = 120 gal. = ~16 cu. ft.
You observed 0.07 in. = ~ 0.0058 ft.
16 / .0058 = ~2750 sq. ft., for example a square ~52 feet on a side.

If your actual zone coverage was somewhat less, that’s likely explained by your well pump pressure and piping loss giving a pressure at the heads that’s less than the pressure for 1.5 GPM.


Well! at least you’ve got evidence it is that low.

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I think I did my math wrong. On my container I was using it has an application rate formula. So I wasn’t using that. I was taking the literal depth on the container. What I should of done was use the application rate. The formula was depth times 60 divided by 20. When I do that it gives me 0.60. Which is much better. The volume inside the container makes a difference.