ET - Information & Discussion

Discussion in 'Irrigation' started by Kiril, Jul 22, 2007.

  1. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,308

    Given the current hype over ET based controllers, I think it is appropriate tio begin this thread to discuss ET.

    For those interested in the complexities behind accurate determination of ETc and understanding how the current ET controllers fall somewhat short of achieving that, a review of what ET is and how it is determined is needed.

    The following paper presents an in depth discussion of ET.

    Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56
  2. Kiril I will study this in depth i promise BUT let's also compare this to HO water management, Yard service water management, landscape contractor management, fertilizer service management, suffolk county anti-anti-syphon valve management and not just a soil moisture sensor vs ET discussion.
  3. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,308

    Sounds good to me. I intended this thread mostly for discussion of ET, and not so much as a comparison of the different methods of determining irrigation schedules, but since the topics you mentioned all apply, then why not. :)
  4. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,308

  5. JimLewis

    JimLewis LawnSite Fanatic
    Posts: 6,841

    Our company switched to installing systems that are build with Water-Management in mind about 2 years ago. We always install PRS type heads, water savings nozzles, rain sensors, etc. with every system we install. Our customers have responded very well to it.

    In moving this direction, obviously ET controllers / managers are something that have caught my attention. But we haven't yet implemented them yet. There are some challenges with implementing them on a residential irrigation system.

    See, we only install systems for residential properties. And in our area, most of the homes are on 10,000 sq. ft. lots - smaller lots. So the systems are fairly small (6-10 zones or less) and the price point is generally around $4000 - $6500.

    Being that we only install Rainbird stuff, I've been looking at the Rainbird ET Manager. It is said to be the only ET device on the market that takes into account the entire ET equation (solar radiation, temperature, wind, rainfall, and humidity). But I will admit, I heard this from Rainbird people. I haven't checked the other ET controllers out very much to see exactly which part of the ET equation they take into account.

    The thing with the Rainbird ET Manager is the price is so high. We can purchase it for around $750. And I probably wouldn't sell it for less than $950. Then you add labor (and it's not a quick, simple install) and the price to add one of these to a new system is well over $1000.00. I'd probably sell them, installed, for around $1250. So the problem is most people wouldn't pay an additional $1250 for that. If they are paying $4000 or $5000 for the entire irrigation system, then an ET manager is an upgrade equal to more than 25% the cost of the entire system. Most people aren't going to go for that.

    The good news is that local water districts are starting to offer some serious incentives for these. One in our area will give the consumer a $200 rebate on their water bill OR a $200 check (cash-money!) if they install one of these. So that's a start. But it's still so expensive that most customers probably wouldn't go for it.

    So I guess I am waiting for the price to go down. But I am very interested.

    I have one of the Rainbird ET Managers here at my house, in my garage. But I haven't had time yet this year to install it yet. We get free service for it too, in our area. But again, haven't had the time to hook it up and program it yet.
  6. Jim we are installing an ET manager at the Dallas Arboretum as part of a water-sense project sponsored by the TNLA and Dallas Irrigation Assoc. It takes time to monitor these things but i'll give you my 2cents after the install. On small yards I prefer the WM smartline because it has an onsite monitior but it is definitely not true ET. Combines some temp data with historical but I've been pleased with the results. I'm going to take a closer look at the soil moisture monitors.
  7. JimLewis

    JimLewis LawnSite Fanatic
    Posts: 6,841

    Let me know how it goes with the ET Manager.

    Yah, I've seen the soil moisture monitors too. My only problem with them is where do you put them? In my area, each zone can be quite different. One side of the house could get lots of sun and quick drainage where another side could get little sun and poor drainage. Which side of the house do you put the sensor on? Or do you install one for every zone? If so, that's a serious PITA.
  8. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,308

    Yea, their interpretation of the ASCEstdPM equations. Looking at what the manager does, IMHO it is a huge waste of money.
  9. Kiril that doc is 70 pages. Just explain in a few sentences why it's a waste of money. Your interpretation is important to me.
  10. Mike Leary

    Mike Leary LawnSite Fanatic
    Posts: 21,987

    Makes me want to return to the thrilling days of yesteryear. Kiril mite need
    his own web site...."Overkillirrigation.duh".:dizzy:

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