# Precipitation rate vs flow rate vs in/hour -- circular logic with calculating precipitation rate

I believe there is some circular logic going on here. Within the custom nozzle configuration, the prompt is requesting a “flow rate” metric. However, there is a support article that discusses how custom nozzles use the flow rate to calculate precipitation rate. The issue here is that nowhere in the software do you specify the # of heads/emitters. Thus, the equation cannot be calculated correctly. It would be possible for one to calculate precipitation rate manually using the formula, but there is nowhere to input this figure. Furthermore, the catch cup test can tell you how many in/hour of water your yard receives, but this is quite different than flow rate. A catch cup test only tells you the efficiency of your system, not the flow rate. No where can I find how to calculate flow rate per nozzle other than my taking the meter total over a 15 minute duration, dividing by the number of heads/emitters, and then multiplying by 4. This would tell you gph for entering the flow rate, but once again, mathematically, the software would not have enough information to calculate precipitation rate.

Any ideas???

So, I think I figured out the confusion here. On the web version, when creating a custom nozzle the software requests a “flow rate”.

However, the mobile software (Android or iOS) requests a “PRECIP” figure. Assuming this means “Precipitation Rate”.

Reviewing the support article here, it appears that “flow rate” and “precipitation rate” are used interchangeably. However, these are NOT synonymous terms. In fact, there is another support article titled How do I calculate my precipitation rate? which states that “Custom nozzles use the precipitation rate (PR); but this is not the same as the flow rate.” The circular logic here is that precipitation rate USES flow rate in it’s calculation, and thus by logic they must be mutually exclusive of each other. One could not provide a true FLOW RATE in the software as there is nowhere to under the number of heads/emitters. Thus, if this truly should be a PRECIPITATION RATE entry, then it should be renamed as such. I shouldn’t have to assume this as they are different.

My recommendation, however, would be to use a FLOW RATE metric AND # of heads/emitters. This way, the already-entered square footage (area) measurement can be used to CALCULATE precipitation rate. Furthermore, the “nozzle” should identify a SINGLE nozzle and NOT the entire zone. By using precipitation rate, it’s a “zone” setting and not truly a “nozzle” setting. Semantics, maybe, but either way it’s quite confusing.

I don’t think that will work. I believe that the custom nozzle needs a PR rather than GPM. The difference in the web app unit ( wrong ) vs mobile needs to be fixed as it’s confusing. @emil ?

@JBHorne, thanks for bringing this to our attention. We need to correct this typo on the custom nozzle support article. The equation outlined in the “How to calculate my precipitation rate” outlines the variables needed to create a custom nozzle…

Ah, good catch. It should be precipitation (precip) rate, not flow rate. This helps to explain the confusion you encountered. We’ll fix this.

Agreed. A “custom nozzle calculator” to aid in calculating precipitation rates would be a great tool.

We apologize for any confusion. If I’m understanding correctly, you’d like to see the name “custom nozzle” changed to something that better represents the fact that it’s a collection of nozzles and not just one nozzle?

@ronjonp, correct – we have to convert the flow rate to a precip rate. However, I believe @JBHorne is recommending we capture flow rate and # of heads/emitters to auto calculate the precip rate given square footage is saved in the advanced settings on a zone by zone basis.

Very confusing, I agree. We need to correct this. Will forward to the web team to review.

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