My Rain Sensor Actually Works!!

Discussion in 'Irrigation' started by HazyDavy, Jul 20, 2005.

  1. HazyDavy

    HazyDavy LawnSite Member
    Posts: 102

    I just got me a new irrigation system last week, which included a rain sensor. I had my doubts as to whether it would work, but apparently it does. We got 2 inches of rain last night and my sprinklers didn't run this morning. I checked out the controller and it said "off".

    Pretty cool!!!!
     
  2. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    Yep, gadgets are way Kewl, get back to me on how quickly it turns your controller back on after that 2" rain. My money is on 36-48 hours and if it was a good soaking 2" rain, I want that controller off for a week. :)
     
  3. HazyDavy

    HazyDavy LawnSite Member
    Posts: 102

    It watered this morning. Didn't take long. Keep in mind I live in NC, it was sunny and 94 degrees yesterday, and my yard gets lots of sun.
     
  4. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    yeah, that's why I don't push sensors. They are neat for making sure you don't water IN the rain, but after that, they are pretty much worthless in my opinion. From that 2" rain, you should have saturated the available water in the top acre foot of soil the grass feeds from. That means to me that you are off for a min. of 3-4 days and up to a week depending on the time of year. It rained good here Tuesday. My customers (well, the ones who follow instructions and don't like to pay for extra water) will have used the rain delay for 3 days from that rain and will be fine. The Temps here are near 100 and the heat indexes are pushing 110-115. Even with that kind of weather, a .5" watering cycle every 3 days will provide enough growth you don't get out of mowing grass.
     
  5. HazyDavy

    HazyDavy LawnSite Member
    Posts: 102

    Well, I was always told you are supposed to water deeply and infrequently, but that doesn't seem to work. I've tried that the last 2 years and my lawn keep dying on me. I'm trying to establish a new lawn, and the soil here is hard red clay. The guy that installed my system said I should water daily this time of year. The guy across the street who has a beautiful established lawn waters every other day. Personally, I think this every day watering is an overkill, but I think every other day is the way to go when you're in the dead of summer.
     
  6. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    There you identified your problem. Clay soils are very tight. Depending on how your system is nozzled (i.e. how long does it take to achieve 1/2"), you need to reduce your individual station cycles (run times) to as little as 5 min for sprays and 15 min for rotors. Then run each zone 3-4 times on the scheduled water day. A min of one hour between run times. If you have a 4-6 zone system, the delay between waterings is easy. Once the system has cycled through, it is ready to run again. You can do the math and program the actual start times, or in most cases, a digital controller will "stack" those overlapping start times and run them out in order. So, if you have a min of one hour total run at the 5 and 15 min run times, then just program four starts one hour apart. If your controller only allows 3 starts, increase the amount of run and only use 3 starts. With only 3 starts, you may still be "wasting" some water in order to get enough water down to do a thorough watering.
     
  7. Harry0

    Harry0 LawnSite Member
    from NJ
    Posts: 223

    Here in southern NJ with sandy loam-you will start to see stress after 2 days of no rain or irrigation. You must water daily when temps exceed 90. If you wait 7 days you will have started to put bluegrass in dormancy and permanent damage to other turf. In most towns around here(maybe statewide)they are mandatory. I install one with every system.
    Harry
     
  8. HazyDavy

    HazyDavy LawnSite Member
    Posts: 102

    I have 4 zones. 3 of them use sprayheads and put down .25 inches in 10 minutes. The other zone is on rotors, but there are 4 of them and it puts out .2 inches in 10 minutes. Probably smaller amounts in some areas. He wanted the sunny areas to get more water. I run the 3 sprayhead zones for 6-10 minutes each, and the rotor zone for 15 minutes. My total watering time is 39 minutes.

    I had mentioned to my irrigation guy about watering each zone for a few minutes to wet the soil, then come right back with another watering, but he didn't seem to buy into that strategy. Just told me to water every day. I actually skipped watering today because I think it's an overkill.

    If I go with your method of watering 3-4 times over the course of the morning, how often would I water? Weekly would probably be too long in between waterings.
     
  9. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,992

    You have to experiment a bit. The idea is to send the water deeply into the soil. The first watering saturates the soil as deep as it can. At this point the water isn't penetrating the saturated soil, but just rolling off. The denser the clay, the shallower this saturated area is. You wait a while, during which, the water is penetrating deeper down. The next cycle will re-saturate the surface soil, and the subsequent waiting period will see even deeper water penetration. A third or fourth cycle will get the water even deeper down.

    Deep water penetration is what this will accomplish. The grass roots will follow the water. Deep roots equal a healthier lawn. Try to do this watering every other day. Or even every third day, if possible. On slopes in clay soils, it's a very useful practice.

    Given the ability of a customer to mess up a controller, you have to allow for contractors not being eager to see homeowner attempts at more complex programming.
     
  10. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    Wetboots explains it very well. The agronomic answer is to water as deeply as possible and then not water again until the soil is dry enough to enduce stress. I know, hardly the answer for a system that is supposed to be "automatic". I like 3 day intervals when the temps exceed 90 on a continous basis. If you experience mid 80's, I believe you can get by on every fourth day. In the spring and fall, I have my customers cut back to every fifth day. You are the one at your site day in and day out. How far you stretch between waterings is a judgement call factored by how much water can you get into your soil on water days, how "green" do you want that lawn you are watering, and the specifics of the micro climate (soil,shade, sun, etc.) that is your lawn area. You seem to be grasping the basic concepts well. Good luck!
     

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