Add Number of Heads on a Zone for Accurate GPM

As a mechanical process controls engineer, I would recommend avoiding any scheme that works from first principals and rather use systems that work on directly-measured system outputs.

What do I mean? Well the best solution recommended is to let the user input the number of gallons per minute each zone uses, and have the system multiply that by the number of minutes to estimate how many gallons were used.

A second best solution would be to let the user enter the square footage and the watering rate (measured in inches per minute by putting cups in the yard) to let the system estimate gallons per minute. Because well-designed sprinkler systems try to get the same rates, a default inches/minute could be used (like in the current system). Here, youā€™re taking some fairly direct output measures and making the simplest possible assumption (uniform sprinkling) to get the magic number.

Though it may feel more attractive and cooler, the likely worst (most inaccurate, most likely to be wrong) method would be to count heads and work from a flow per head. If you knew how much came out, that would work. However, and as noted, the amount of flow will vary depending upon watering pressure and a flow rate that is typically adjusted using some sort of screw on top of the head. It would be nearly impossible to calculate the flow and practically really hard to actually measure how much a given sprinkler head puts out on a per minute basis. <As an aside, this flow per head MIGHT work for drip systems where flow/area doesnā€™t make any sense what so ever.>

These general ideas of measuring the simplest thing are, in my opinion, the biggest problem with the Rachio system. Thereā€™s too many settings based upon first principal variables. For example, think how nice it would be if you could just say ā€œincrease water by 25%ā€ OR ā€œmy grass needs more waterā€ instead of whatever you do currently to trick it into giving you more water. I would highly recommend to the Rachio folks to sort of walk through each use case to see which solution comes closest to getting to this ideal of working from directly observable system outputs.

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I know your suggestions are definitely accurate, but not realistic for the average homeowner. Rachio uses default values for spray heads. I think this is good enough for the average homeowner - just to input the nunber and type of heads. I realize the people on this forum are very intelligent, but the average consumer is clueless when it comes to irrigation.

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I would think the easier solution to the guesstimated water usage would be for the controller to integrate with an electronic water meter placed before the irrigation manifold.

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Yes it does, Iā€™m using oneā€¦

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Yes, this could be a solution. But I donā€™t see it as realistic because of the cost of these devices. Plus, this is a feature usually reserved for high-end central control systems like Toro Sentinel, Rain Bird IQv3.0 or Irritrol Rain Master Eagle Plus. Do you have a flow meter in mind?

We use the RainBird FS series sensors in conjunction with RainBirdā€™s IQ control center. Theyā€™re spendy for sure but if your wanting accuracy then look no further and buy their smaller model like the 1" FS100.

I suspect one problem with this method is there may be a point of diminishing returns where someone added one or two too many heads on a zone. At that point even with a regulator the zone may be unable to maintain a steady pressure state due to a lack of water volume being supplied, and all of the heads lose some output volume which brings you right back into having to measure and create custom heads in the program.

edit

p.s.

Iā€™m not against the idea, just looking at it from Rachioā€™s side and why it may not be as clear-cut as a win as weā€™d like it to be.

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@scorp508 You hit the nail on the head- it feels like an easy fix, and then these wrenches keep working their way in and blowing up the solution :joy: Regardless, the amount of activity on this thread (and many others) makes it incredibly clear that our current solution could be improved.

Interesting discussion. Iā€™ll add one more degree of complexity. For my (pathetically small) yard, I need to use a series of smaller nozzles to cover the yard that lays beside the garage (approx 1.5 meters wide, stretching around 8 meter). Iā€™m sure a lot of people have areas that require additional nozzles just to cover oddly shaped parts though. That means either adding even more zones to the plan, or adding nozzles with different sizes to one zone.

Iā€™m just going to read the water flow meter :slight_smile: But do we have a setting to adjust actual water usage in the app then? Or is that still a feature request?

There are 2 basic approaches to measure or calculate water usage - using precipitation rate x area, or using gallons per minute. Both approaches can be either measured or estimated using manufacturerā€™s nozzle specs (perhaps adjusted if you know how much each nozzle was adjusted).

Of course a measurement is better than an estimate. I have a water meter, but the city reads it electronically every 4 months, so I canā€™t get a real GPM measurement from my meter.
I would only go to the trouble of setting up catch cups to measure precipitation rates if I wanted to adjust my nozzles, not just to measure flow for rachio stats. However, it might help me tune my flex schedules.
So, looks like an estimate for me. None of my zones are perfectly rectangular, and none have all heads with the same flow rate. Many of the nozzles are variable arc, so the flow depends on the arc. Some heads may have had radius reduced, so flow would be less. I can estimate the GPM flow from each head and add up the total flow for the zone.

I am not a fan of having the precipitation rate defaulted by nozzle type, instead I would enter it zone by zone. I bet that most zones have odd shapes, irregular head placement or imperfect head coverage, so the manufacturer specified PR is not achieved. However, the efficiency for the zone can be reduced for irregular zones.

I think the product suggestion is to have total zone GPM, Precipitation rate and zone area as 3 zone parameters. 2 must be entered and the third is derived by Rachio, using the other 2. The user can choose which 2 will be entered, and which will be derived.

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I have one zone that fails to meet any sense of decency to the way it was laid out due to both the irregular area it tries to cover as well as the number of heads jammed into the area for both itself and neighboring/overlapping zones. It also has very varied coverage along its perimeter compared to in the middle of its field. Perimeter cups catch <10ml over 10 min while center field cups catch 16-20ml once the zone and overlapping zone are run. Iā€™d welcome the ability of doing some kind of per-zone override for GPM, but at the end of the day I think that particular zone is going to be all about compromise. :slight_smile:

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I really like the idea of users being able to choose which they provide, and we back into the third. That way users are entering the two they are more comfortable with, and hopefully hey are more accurate!

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I did not read all of the above, but when I installed mine, I did the "Log meter reading, run for 5 minutes, log meter, run next zone for 5 minutes, etc.+ then just created new heads with custom PRs. Itā€™s not perfect, but much closer than out-of-box. That said, if the software, DURING SETUP, simply asked for a meter reading before each zone fired, it could do all the math for us and make the product much more user-friendly and SIGNIFICANTLY more accurate.
NOTE: This assumes the owner has access to the meter.

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Yes, this is perfect. It is a very good way to calculate PR. Here is the Rachio support article:
https://www.google.com/url?sa=t&source=web&rct=j&url=http://support.rachio.com/article/316-precipitation-rates&ved=0ahUKEwjA2L3op_jUAhVVImMKHaEaDkUQFggzMAI&usg=AFQjCNHgNjT2jX5IKbGuOK8SOTOTrmL1_A

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Right. I have 10 zones. It was a pain to sit by the city water meter and operate each zone for 5 minutes and then create custom nozzles with the PR for each zone. But just today I audited the subsequent meter readings versus Rachio and they were in good agreement. Kudos to Rachio for making this possible and reasonably convenient. Now I can manage my usage with confidence.

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Even though Iā€™m on well water Iā€™m starting to feel like a meter would be a nice thing to still have.

If you Google flow meters for well water, you can buy one for about $100. They are basically totalizers like the water meter your water utility uses. I would recommend having a plumber install it. But it would have no connection to the controller. You would take readings to record usage.

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EBay has meters with 1/2in couplings for $30 and 3/4in for $40

Ebay concerns me. I am skeptical of ebay.

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Of course itā€™s your choice. I have three installed measuring different aspects of my rainwater collection system for about two years now and they are doing just fine. I buy a lot of stuff from eBay but I agree that if the price is too good to be true, it probably is a scam, you need to be sensible.