Nozzle Type is a clumsy way of specifying flow/precipitation rate


I’ve set up 6 zones so far, and for each one I’ve had to specify a custom nozzle type to set an accurate precipitation rate. In most cases, I have pressure-regulated nozzles with well-documented output depending on nozzle overlap, so I know the precipitation rate. In other cases, I’ve measured the flow rate. And in all cases I know the area of the zone. There is no reason that Rachio should need to know my “nozzle type”. Using common nozzle types as a way of simplifying things just introduces large errors into estimates of water flow and precipitation rate.

This issue has been brought up before, and in a previous post jkb wrote:
“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.”

That makes sense. A table of the precipitation rates expected for common nozzle types can then be made available as a helpful guide, but you’ll need to explain all the pitfalls of using that, including the extent of nozzle overlap. Generally, the manufacturer of the nozzle provides such information, but even then it is not always clear what assumptions they’ve made about overlap.


Precip rate = (96.25 x Flow Rate(in GPM))/Area(in sq ft)

With that equation you can calculate the exact precip rate that will cause the Rachio to get exactly to your flow rate and zone area.


“Precip rate = (96.25 x Flow Rate(in GPM))/Area(in sq ft)”

Well sure, that’s what I’ve been doing. The point is that it’s silly to have to assign a precipitation rate to a pretend custom nozzle, and as jkb proposed, we should be able to provide any 2 of the 3 factors (prec. rate, gpm, or area) to Rachio. Also, forcing users to create custom nozzles just reinforces the notion that nozzle types actually correspond to well-defined precipitation rates. But that is definitely not the case, with such rates being a function of nozzle overlap, arc, pressure, etc. All the work Rachio does in tracking soil moisture, gallons saved, etc., is made unreliable by the gross approximation of using an approximate precipitation rate corresponding to a typical nozzle. imho


I don’t get how giving a precip rate is any less accurate than giving the other two figures in the equation. No matter what you end up in exactly the same end result. Honestly precip rate and doing a catch test is more accurate in my book because then you actually start to get an understanding of your coverage efficiency rather than just I sent this much water into this large of an area.


Totally agree. The catch can test is real world PR.


“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.”

i.e., providing a precipitation rate + area should be one of the options, but it is no better than providing a flow rate + area, or a precipitation rate + flow rate… just depends what info is most readily available

Anyway, the point is that having to specify a custom nozzle type just to enter the precipitation rate is both clumsy and misleading. Rachio doesn’t need to know anything about my nozzle or sprinkler types to do its job, just any 2 of the 3 params (prec. rate, flow, area).

A separate table indicating what types of prec. rates are associated with typical nozzle/sprinkler types might be helpful, but then they would have to explain how complex the relationship really is (pressure, arc, throw, overlap, etc.). It would probably be better to link to nozzle manufacturer sites and promote direct measurement of prec. rate, flow, and area (as you guys are suggesting) than to try to base things on just a nozzle type. But none of that requires Rachio to know anything about my nozzle type(s).


Actually it does need to know about the nozzle and precip rates to know how fast the water goes down and if it needs to add pauses to give the water time to absorb based on soil types and grade angle. Its pretty clear to me that the actual nozzle type doesn’t really mean much compared to the actual precip rate number.

And for most people they don’t care to really get ultimate accuracy they just want close enough so they choose something near to what they have and they move on with life.

If you want actual accuracy you can go to the manufacturers to get the precip rates based on spacing and what not and put it in. Anyone who is capable of looking up the precip rates on their own should be capable of putting in their own head type.

While I’d be willing to bet that putting in other parameters may be available in their new version of the software 100 years from now when it comes out… There is no way that this will make anything more accurate because you’re not taking into account pressure variations and spacing problems that may lead to coverage efficiency problems.

The best way to do it is to just do a catch test and find out coverage issues and to then put in a custom nozzle that matches YOUR system. This is already how the app is built and with a very simple calculation people can use any other sets of numbers and end up in exactly the same place.


"Actually it does need to know about the nozzle and precip rates to know how fast the water goes down…"
No, it needs to know precipitation rate and area (or prec. rate and flow rate, or flow rate and area). It doesn’t need to know anything about the nozzle type.

We are in the “product suggestions” area, not the “how to make a poorly designed interface do what you need it to do”. It would be an improvement to allow direct entry of 2/3 of either prec. rate, flow rate, and area. Beyond that, the Rachio team can play around with supporting entering nozzle type to get to the same basic info, but then they’ll have to explain the myriad of factors connecting nozzle type to prec. rate, including pressure, arc, throw, overlap, etc. I think that would be a waste of their time (just as these custom nozzles are already a waste of their time).


I’d bet that most people just choose a nozzle type and don’t mess with precip rate or any of the other settings as its too much of a pain for them. Thus the nozzle type exists. It just turns out that the nozzle type is the easiest way for the software to allow a user “who wants to” to provide more accurate precip information.

Changing that to make it even more complex with an equation and expecting users to understand that they are required to enter two variables and it can be any two variables and the others will be calculated and expecting accurate results is a step backward from what it is today in my opinion.

Honestly nozzle type and a custom nozzle is nothing more than a way to enter a precip rate while still keeping things simple enough for the every day user. Getting wrapped around the axel and wanting to think about arc differences and overlap and all that isn’t necessary because you just put in the actual precip rate. If you want to guestimate that with flow and area then by all means do so but realize that doing so is no more or less accurate.

I suggest that the changes you’re proposing would cost them quite a bit more money in service calls. Where as most people are totally fine and happy enough to just choose a gross nozzle type and move on with life.


I’ve never heard that one. I like it. :grinning:


No, the easiest way to enter a known precipitation rate is to enter the known precipitation rate, not a fake/custom nozzle type. And encouraging users to choose a nozzle type to roughly estimate precipitation rate just degrades the performance of the program, corrupting all of its efforts to accurately project scheduled watering times, soil moisture content, gallons saved, etc. (I mean, I thought that was a big selling point of Rachio - accurate predictions, saving water, etc. - all of which is corrupted by bad prec. rates.)

Of course, you’re right, most people simply choose a nozzle type and forget about. That’s because the poor interface leads them to make that mistake. All of which is unnecessary and easily fixed: add direct entry for prec. rate, and save prec. rates from any existing nozzle info. There is no “formula” to learn, and they are already entering a prec. rate in the bogus nozzle type, and an area elsewhere. (The only new number would be the option to enter a flow rate, which in many cases is a number directly measured.)

If the Rachio folks also want to present an interface for choosing nozzle type to estimate prec. rate, then they should do it right, and not the dumbed-down way they are doing it now. But this is very product- and system-specific (i.e., pressure dependencies, arc/throw dependencies, arrangement of sprinkler heads, number of heads, etc.). That sounds way too complex to support well.


I agree that a catch can test is the best, but the average homeowner will not grasp this.


After reading the discussion, I am thinking that adding Precip rates and Flow as ‘advanced’ zone parameters would fit the existing interface. Compare this to Soil Type and Available Water. The nozzle type provides the default precip rate, but it can be overridden as a zone parameter. That would save creating ‘custom’ nozzles in order to override the PR.

I think all of the advanced parameters (which are either defaulted or derived) should have a reset button to remove any user overrides. A simpler version could be a single reset button that resets all advanced parameters for the zone.

So the Precip rate which is used to determine watering times can come from one of:

  • default from nozzle type
  • calculated from Flow rate and area, if both are overridden in the zone info
  • as entered’


Something like what jkb is suggesting makes sense to me.

However, please don’t require us to also enter a nozzle type since I know that there is no simple relationship between nozzle type and zone prec. rate. The prec. rate will at least depend on the number of such nozzles in a zone, how they are arranged, what pressure is available to each, how each is configured (arc, throw, etc.), the exact type of nozzle (i.e., the specific brand and part number), etc.

For example, one of my zones is a relatively narrow strip in which I have RainBird HE-VAN 15 nozzles on sprinkler heads limited to 30 psi each. The pressure limitation and type of nozzle (supporting a prec. rate not affected by arc size) should make this a simple case, but the total prec. rate is still dependent on the number and configuration of the sprinkler heads in the zone. With total overlap and square configuration, the zone prec. rate should be about 1.5 in/hr, but with nozzles on one side only (what I’m doing) the rate is 0.75 in/hr, while each individual nozzle is putting out only about 0.5 in/hr. So, you see, it make little sense to associate a broad nozzle type (“fixed spray head”) with a zone precipitation rate.


You are very in tune with your irrigation system!

I really like those nozzles. They perform very well in close to the head watering and throughout the throw coverage.

Rachio has the “fixed spray head” PR at 1.5 in/hr. This seems to be based on 30 psi, which is the manufacturer recommendation for spray heads. Not all irrigation systems or zones are pressure regulated to manufacturer recommendations for zone pressure. This too could be causing some over watering issues for some people.


For that rate, the manufacturer (RainBird in this case) is assuming 100% overlap of sprinkler throw radius (i.e., 4 sprinklers in a square, positioned exactly 15 feet apart for the HE-VAN 15s). As noted, I don’t use them that way for that particular zone, having only one row of sprinklers on one side of the strip, giving about 0.75 in/hr. Moreover, with experimentation, I found that, at 30 psi, the HE-VAN 15s throw about 12 feet, the HE-VAN 12s throw about 10 feet, etc. So I spaced the 15s about 12 feet apart, and double-checked the overall flow rate to the zone to verify the precipitation rate. So, anyway, it’s easy to see that entering a custom nozzle as “HE-VAN 15” and assigning it a (zone) prec. rate of 0.75 in/hr if just confusing, since the zone prec. rate is not a simple function of the nozzle type.

Most of my zones are like that, requiring entry of a misleading custom nozzle type to define what should be a directly entered prec. rate (or flow rate and area). For example, one of the zones is connected to an above-ground pattern sprinkler (an impact sprinkler which allows adjustment of throw distance based on angle - very cool). The water flow to this sprinkler must be adjusted to ensure that the throw range stays within the irregularly-shaped zone. And by measuring the water flow and area of the zone, I can calculate a prec. rate. However, having to enter that as a custom nozzle type is nonsensical. There is no typical prec. rate for such a sprinkler, it depending mainly on adjusted flow rate. And I should be able to enter flow rate and area directly, without the need to create a custom nozzle type, or to have to precalculate the prec. rate.

Another example is a zone where I’m using Hunter 9SST nozzles, throwing 9’ x 18’, at 1"/hr without overlap. iow, these nozzles are designed to water a strip without needing to have their throw overlapped, meaning you need fewer nozzles per zone (compared to HE-VANs, for example). So they’re still in category of “fixed spray head”, but operate differently with respect to positioning and number. This case comes closest to where a custom nozzle type “9SST” corresponds to a well-defined prec. rate, but that’s not because its in the category of “fixed spray head”, but rather because the nozzle (with my fixed pressure spray head) has been specifically designed to provide a consistent prec. rate without overlap.

So, anyway, you can see why I’m skeptical of specifying custom nozzles as an indirect way of entering prec. rate. And for anyone less experienced, picking a nozzle type as a substitute for knowing actual flow or prec. rate probably just leads them to corrupt most of what Rachio is trying to do wrt water management. imho


Really the easiest way to determine the usage of each zone is to simply run a zone for 1 minute and record the water usage through the water meter. Multiply the gallons used by the minutes that this zone uses.


For the more advanced people: the nozzle type is important because different types of nozzles have different efficiencies. Drip is far more efficient than a standard overhead spray nozzle. That efficiency helps determine actual run times instead of run times for theoretically perfect systems with 100% efficiency (all water is applied exactly where it’s suppose to go, in a completely uniform pattern).

For the general population: selecting a general nozzle type is simple and for all intents, can get pretty close to actual PR. How many people do you know that can figure out the gpm a zone is using? Quite a few probably struggle just figuring out the sq.ft… How many are going to invest in catch cans that get used once?


My $0.02: Those of us who understand the issues of computing a true PR, or the mathematical truth of only needing 2 of 3 parameters in order to compute the third are able to use any interface Rachio provides to achieve our configuration goals. I have not been confused by what Rachio is trying to do.

However, the average homeowner is likely much more comfortable thinking “nozzle type” than anything close to mathematics. From a business/support/user satisfaction perspective, I suspect Rachio is better off with the current method.


As shown by my previous examples above, there is no straightforward relationship between zone PR and either broad or specific nozzle types, due to a multitude of factors, including nozzle/sprinkler number and spacing. And there is no good excuse for Rachio to lead users to think otherwise, nor for any of us to have to work around a poor interface to get it to behave properly.

Honestly, I think Rachio should disable all of its water volume/balance calculations if the user is unable to enter reliable values for PR or GPM, and area (i.e., just use it as a timer). As others have noted, it’s just not that difficult to get this right (enough) by either measuring flow directly, or having a good understanding of your nozzle types and sprinkler heads (or by measuring PR directly with catch cans).

I love Rachio, but I also don’t think it’s helpful to its future success to try to hide/defend its current flaws/shortcomings.