Rotary nozzles - shorter spray length along the edge

Discussion in 'Irrigation / Sprinkler Forum' started by k9mlxj, Sep 28, 2011.

  1. k9mlxj

    k9mlxj Member

    Jan 7, 2011
    Bay Area CA
    Hi there,

    Two years back I installed Rainbird's rotary nozzles to replace the traditional Toro 570 sprinklers due to too low water pressure (around 20 psi) and lack of coverage. Things improved a lot after changing out to use the Rainbird's rotary nozzles as they could reach far greater distance given the same water pressure and the nozzles reduced water pressure much less (per nozzle) compared to the Toro's 570 nozzles. Water pressure was more usable -- around 28 psi with the Rainbird rotary nozzles.

    This summer has been a hot summer, and I am starting to see dry patches -- right along the edge of the lawn.

    When I looked closer, I realized the Rainbird's rotary nozzles shot out fairly far--except when the spray moved close to the edge--the spray length shortened significantly at that point (e.g. from 20 feet to 10 feet).

    This resulted in a 6 inch wide of long dry strip along the edge. The hot summer exposed this problem as that area received less water than the rest.

    I experimented by changing it out to use a Hunter MP Rotator MP3000 today. But the MP3000 exhibited the same problem where the spray length shortened when it got closer to the edge.

    The only way I think I can solve this is to adjust the MP3000's arc to cover wider than the edge of the lawn, so that the last 6 inches where the spray length gets shorter as it would get close to the end of the arc is outside the lawn's edge. This would create an overspray problem however.

    This sounds an odd solution -- and wastes much water. I wonder if anyone has any other suggestions?

    Don't know if there's a better nozzle that provides these same benefits as the rotary nozzles and also keep the edge coverage even (heard about Toro's Precision Spray nozzles, but it can only reach 15 ft max -- I need something that can reach 24-26 ft).

    Also the runtime with the Rainbird rotary is fairly long with the large lawn, so if I can improve to get a bit of shorter runtime to achieve the same precipitation that would be really helpful. It is taking 5 hours to irrigate the front lawn now.

    Current sprinkler head-to-head distance is about 24 feet on the main lawn.

    How about Toro Precision Stream Rotating Nozzle? Anyone knows if it covers the edge better than MP Rotator and Rainbird rotary nozzles? Or Rainbird's 3500, 5000 series?

    Last edited: Sep 29, 2011
  2. Mike Baron

    Mike Baron DIY Junior Member

    Sep 30, 2011
    National Sales & Specifications Manager for Water
    Glendora, CA
    My name is Mike Baron and I worked for the company that originally introduced the MP Rotator; otherwise known as the Walla Walla Sprinker Company from 2002 to August of 2007. Before that, I worked for Rain Bird for 20 years in marketing and product development. For the past four years I have been working for Toro Irrigation and have been heavily involved with the development of the Toro Precision Spray Nozzles and the Toro Precison Rotating Nozzle line. I mention this to let you know I have some experience with the problem you have identified.

    Your original problem with the RB Rotary nozzles was aggravated by the fact that this nozzle is fixed arc. You can't adjust the pattern. It is what it is. If your heads are even just one or two inches from the edge, the fixed arc Rotary Nozzle is going to have an edge issue. When you switched to the MP3000, which has a slightly higher flow rate - about 0.3 gpm per nozzle. If you have 10 heads on a line, that means you increased the flow rate by 3gpm. If you adjusted the arc a bit, that increased the flow rate even more. Part of your overspray problem may be simply due to a lower than ideal operating pressure. If it is below 40 psi, you may not be getting fully developed streams which would make your overspray problem worse.

    Hunter manufactures a "pressure gauge tee" originally developed by the MP Rotator people, which allows you thread it onto the pop-up head (if the stem is male thread) and then accepts a 1/4" threaded pressure gauge. You thread the nozzle you just removed from the head back on top of the "pressure gauge tee", turn on the zone and then clearly read your operating pressure. Let me know what that is, how many heads you have on the line, and what pattern each MP3000 is set at and I will be able to determine your flow rate. With pressure and flow information, I will be able to give you a good recommendation on how to minimize your overspray.

    It's too bad we didn't connect two years ago. I could have given you samples of the new Toro Precision Series spray nozzles. You could have simply replaced your older Toro nozzles with the new more efficient Precison nozzles that reach the same distances as our standard nozzles but with with 30% lower flow rates. That in and of itself would have raised your operating pressure sufficiently to solve your original coverage issues - I think.

    If you want to contact me directly, please email me at I would like to help you solve your issue.

    Best Regards!
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  4. k9mlxj

    k9mlxj Member

    Jan 7, 2011
    Bay Area CA
    Very helpful info! Definitely would contact you offline as I still need to fix the various areas due to low pressure issue.

    With the current zone I'm on, the working pressure is around 35 psi. In the main lawn the working pressure is close to 29/30 psi. I was trying to find something like you mentioned the 'pressure gauge tee' to get the operating pressure accurately. Perhaps tomorrow I can get that tee so I can get some data points to get better calculation.

    All my sidewalk areas (and the whole backyard) still have good old Toro 570 fixed arc spray nozzles as the sidewalk is 80 inch wide and I can't find any side-strip rotary nozzles that'd work on this width.

    Although I like the look of the spray of Rainbird's rotary nozzles (it looks attractive to me -- and my neighbors), the fixed arc is a major drawback as some part of the lawn doesn't match the exact angles available from RB, plus the edge coverage issue where there's really no workaround. At the time I changed out the Toro 570, I was a bit desperate as the lawn was dying due to v. poor coverage (probably due to low working pressure).

    The old Toro's had v. high flow rates. The Rainbird was a rescue as it had much less flow rates, allowing the working pressure to come back up (it was in the low 20's w/ the old Toro's) although as mentioned not w/o flaws (like the fixed arc and the edge issue).

    May I ask--does the Toro Precision Series Rotating nozzle also provide a clean edge like its spray nozzles in the Precision Series? Can it also provide even spray pattern for operating pressure in the 30's psi range? I have been asking around to get this information the past few days.
    Last edited: Oct 4, 2011
  5. SteveW

    SteveW DIY Senior Member

    Feb 11, 2005
    Omaha, NE
    Mike Baron,
    Thanks for your very helpful info! I really liked the MP nozzles when they came out, was surprised to see Rainbird come out with something similar, but had no idea Toro was working on its own version. The Toro version looks like a quantum leap over the others with the adjustability it has. This is good news.

    Over the years I have liked Toro heads and controllers a lot. I used to work for a residential sprinkler installer in the late 70's and remember the first time I put in a zone with Toro's "Stream Rotors." It is a real site to see, those cool rotating streams over a large expanse of lawn, esp when the sun hits them just right.
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