fghunt

How to Measure 1' Water

fghunt
June 23, 2009

What is the best method to measure 1" of water from undergroud sprinklers? Would you use an actual rain gauge or something like pie pans? Is it best to have more than one device?

Comments (30)

  • lamcon

    Usually I see people suggesting using tuna cans to measure the 1" rate. Spread a few out at different locations of your sprinkler to see where is getting more water and where is getting less.

  • skoot_cat

    Tuna cans are best, but any straight sided, same size cans under 5" diameter will work. Place several(at least 8) tuna cans around the perimeter and at random in each irrigation zone the night before your irrigation is set to run. Run your irrigation as normal taking note of the run cycle time for each zone. The next day go out and measure the depth in each can, be sure to write your findings down. From this point you should be able to determine whether you need to run your irrigation more or less to achieve 3/4-1" of water. (example: If you irrigate for 1 hour and have a 1/2" in most of the cans you will need to run your irrigation for 2 hours to achieve 1")

    Remember: All cans do not have to be between 3/4 and 1" If the majority of the cans are between 3/4 and 1" your fine. If you find some that are unusually low you will need to adjust or move some sprinkler heads.

  • organicnoob

    One of the blogs I read had a post a couple of days ago about some myths on lawn watering and the 1" rule was part of the post which included a different way to figure out how much water your lawn needs.

  • andy10917

    That article makes me angry. In the first paragraph, the AUTHOR jumps to the conclusion that "Deep" and "Infrequent" is equivalent to 1" a week. Then he pulls it apart. Most of the people that say "deep" and "infrequent" know that it requires interpretation for different situations like clay, sand, etc. But newer lawn owners insist on specific numbers.

    Let's return the favor - let's follow the author's premise. If a person has been watering frequently and in a shallow manner, then their roots might go down only a couple of inches (I've seen it!). So, if you water only to the bottom of the root zone (2") you will "validate" the idea that you only have to water until it has penetrated 2". Self-fulfilling fallacy! The idea is to get a deep root system that reaches way beyond where the sun can dry things out.

    Some of the author's ideas are not bad, but declaring that other people's specific words mean something other than what they say, and then ripping it apart is just plain bad writing. "Deep" and "Infrequent" means deep and infrequent.

  • bpgreen

    Sometimes, I think people forget that many of the lawn rules are more rules of thumb than rules. Or to paraphrase a recurring line from the Pirates of the Caribbean movie, they're more like guidelines than actual rules.

    I think the inch a week rule is repeated often and we don't discuss how/when to deviate from it as often as we should.

    The best approach is to let the grass tell you when to water. I know that in the summer, an inch a week applied all at once wouldn't keep KBG green here in the middle of the summer when the highs are above 100 and the humidity is in single digits. But in the spring and fall, when it's cooler and more humid, I can often go several weeks without watering.

  • andy10917

    I agree, BP. I think that the idea of Deep and Infrequent is so foreign to many people that see all their neighbors water 15 mins a day every day, that the 1" a week acts to make them realize how far they are from the "center" of a deep/infrequent regimen. I can't tell you how many "what does deep/infrequent mean questions" get asked. I agree, though, that we should ask more questions before answering.

  • organicnoob

    "Most of the people that say "deep" and "infrequent" know that it requires interpretation for different situations like clay, sand, etc. But newer lawn owners insist on specific numbers."

    I think that's the point the author was trying to make. You can't just say deep and infrequent and then give a simple answer because someone only wants to hear a simple answer and hope they figure out how to extrapolate from there based on their conditions. At least that's how I read it.

    Would someone who needs to ask on a forum be able to determine their own conditions to make the corrections to the simple answer? I'd say I'm a bit more informed than them and I couldn't tell you more than my soil seems to have a lot of clay, I think.

    The other point you make is interesting but lets use an example where 1" of water goes down 8" of soil and you have 2" deep roots. Isn't that wasting at least some of that 6" of water where there are no roots?

    There was a note that you might have to measure if the size of your roots change.

    Maybe I let the use of a phrase repeated on TOH sway me. Having "measure twice cut once" drilled into me from that show sure has saved trips to get more material. But running around the lawn twice with a tape measure does make mowing seem like more of a chore than it has to be.

  • bpgreen

    "The other point you make is interesting but lets use an example where 1" of water goes down 8" of soil and you have 2" deep roots. Isn't that wasting at least some of that 6" of water where there are no roots? "

    Yes.

    That's why I will often tell people to change their watering habits gradually. If somebody is watering every day and suddenly switches to once a week, their lawn will probably die. It's best to make the change gradually.

    If you want the grass to develop deeper roots, you need to water past the current root depth, then wait until the grass starts showing signs of stress before watering again. Gradually, the time between waterings will increase, as the roots reach deeper into the soil.

    "Maybe I let the use of a phrase repeated on TOH sway me."

    What does TOH mean?

  • organicnoob

    "What does TOH mean?"

    OMG! u don't watch TOH? lol

    :) I have to remember not to take it easy on acronyms sometimes. I thought everybody on a lawn care site would know TOH was This Old House.

    P.S. I forgot the smiley after the last paragraph. I don't really measure my lawn before I cut it :)

  • bpgreen

    "OMG! u don't watch TOH? lol

    :) I have to remember not to take it easy on acronyms sometimes. I thought everybody on a lawn care site would know TOH was This Old House. "

    Is this a TV show? I don't watch a lot of TV. It's background noise while I'm reading.

  • organicnoob

    "Is this a TV show?"

    Sort of. It's on PBS :) This Old House is a good home improvement show that's been around since 1979. I've been watching it since I can remember. They are like the Julia Childs of home improvement.

    They have a magazine and books too but I haven't looked into them. Can't imagine what it would be like without the heavy Boston accents. Just wouldn't be right learning how to do something without first having someone explain it, followed by someone saying "sounds good!" and then someone saying "beautiful" once it's done.

  • rcnaylor

    I think BP hits the nail on the head. Its a rule of thumb, a general guideline. To treat it as a "myth" is probably further from the truth than the myth.

    The author does make a good point. Water deeply and when your lawn needs it. And what it takes to get it watered deeply and how often can vary greatly.

    I think the "one inch a week" rule of thumb advice is kind of a bridge to get those inclined to just set their system to water frequently and/or on a set schedule to start moving towards the correct way to water, deeply and only when the lawn, soil type, weather, thatch involved, etc result in the yard actually needing it.

  • rcnaylor

    The measuring of what is being applied, whether an inch or any other amount also serves a useful purpose of identifying areas of poor coverage in irrigation systems.

    So, the effort to get "one inch" out also helps for a second reason.

  • rdaystrom

    Watering 1 inch per week can get expensive. If your yard is very large it would be an enormous water bill each month. 1 inch of water per acre is 27,154 gallons. That's 108,616 gallons per month for 1 acre or half that for a half acre yard.

  • fghunt

    WOW - I can't believe the responses here. All I wanted to know was the best way to measure the output of my sprinklers. I used the 1" thing as a frame of reference for the question only. Even me, a narrow and shallow minded neophyte, knows that I may have to water more or less depending on my specific lawn. Heck, I may have to run each zone a different time length to achieve a consistant amount of water accross the entire lawn. Somehow this got way more technical than what I was looking for, but thanks for all the feedback anyway.

  • garycinchicago

    > "Somehow this got way more technical than what I was looking for"

    I take it that means you don't eat tuna then! MUHAHAHHAHAHAHA!!!!

  • lamcon

    What if we tried something more concrete than using tuna cans?

    1 gallon of water = 231 cubic inches

    A 10'x10' patch of land is 100 square feet which is 14,400 square inches. If the goals is to provide 1" of water over that area, one would need 14,400 cubic inches of water for that 10'x10' patch.

    When you divide the area by the volume of a gallon (i.e. 14,400 ÷ 231), you get 62 gallons of water needed to water a 100 square feet of land. That is 0.62 gallons per square foot.

    With that being said, couldn't one figure out the area that their sprinkler covers, multiply that by 0.62 gallons per square foot, and then figure out the time it takes to reach that number of gallons of water? Or maybe you water based more on what the water meter reads instead of the time it takes.

    Anyone ever tried this?

  • bpgreen

    The advantage of using the tuna cans over calculating the area and volume of water is that the tuna cans can identify whether your sprinklers are applying the water evenly. Also, if you've got leaks in the system or your sprinkler heads don't apply as much as they're rated, you don't get an accurate reading.

  • organicnoob

    Measuring and applying the volume sounds like it would be more difficult. Don't most sprinkler timers measure on time? Some calculate volume but I think that's just an estimate. It still doesn't address the issue of different lawns need different amounts of water.

    I left a comment with a link to this thread and the author wrote quite a long reply yesterday as to why the method proposed is better. I haven't had the time to look into everything that was said but at first glance I can't disprove it.

    Has any one looked at the soil the day after applying 1" of water and seen how far it penetrated the next day? I can't try it because of all the rain here. Won't have to water till 2025.

  • lamcon

    My thinking on the area is that you could time how long it takes for the appropriate number of gallons to sprinkle on the lawn. Then in the future, you'd just let the water run for that long. Then you know exactly how long it takes for 1" of water to be applied to that given area.

  • organicnoob

    lamcon,

    How do you measure the number of gallons? Does your sprinkler system have a flow meter that reports back to the controller?

    How much time or how many gallons it takes to reach 1" doesn't seem to matter though. The blog is saying forget 1" altogether.

    "Somehow this got way more technical than what I was looking for"

    fghunt,

    If yo're lucky you ask a question, you get an answer then your thread can becomes a spot to bicker, joke, analyze, expand or even completely change topic. If you're not lucky, you don't get an answer just everything else. Like the group of guys at the hardware store that go on about what the last customer purchased. What they think of it, how they use it, why they think they could design a better one. Sometimes pointless, sometimes productive but mainly something to talk about on a topic you enjoy.

  • lazy_gardens

    Here's the site that explains how ... get a bunch of tuna cans or catfood cans and a rular

    Here is a link that might be useful: How to measure sprinkler output

  • lamcon

    Organicnoob,

    I don't know how your house is set up. In our house, the water meter is right in the basement. I'm talking about monitoring that for the sake of figuring out how long it takes to get to a certain number of gallons of water. Just tossed it out as an idea.

    Frankly, I use the "if it starts to look dry, douse it" method. Works fine for me.

  • organicnoob

    My water meter is very hard to get to and read. It's an interesting idea for those that have easier access but then you need to know exactly how much area your sprinklers cover and then you'd need to be certain you are getting even coverage. It adds more variables. But without throwing out new ideas we don't learn anything new. I think some of the older manual timers work off of flow and not time so that might be helpful to people using those.

    The TOH guys have never steered me wrong and since this looks like it's based on something I've seen recommended on the show. If I have to start questioning the advice on TOH I'm going to have to seriously reevaluate almost every aspect of my life :)

    "Frankly, I use the "if it starts to look dry, douse it" method. Works fine for me."

    Agreed.

  • rdaystrom

    In the original question fghunt wants to know how to measure 1" of water from an underground sprinkler system. This is a good question because it addresses several issues that he should have the answers to.
    1)How long to run a station to get an inch of water.
    2)How even is the sprinkler coverage on a station.

    1a)Sardine cans are so inaccurate I wouldn't consider them at all because they are shallow and much of the water will splash out. You need straight sided regular cans (5 or 6" tall) or a similar container. Rain gauges will work too.

    2a) Place the receptacles at various radii from the sprinkler head. Measure the water depth when the sprinkler turns off and before much evaporation.

  • rcnaylor

    Hey man, you ask a forum full of acknowledged "lawn whackos/zealots" a question... of course you are going to get more than a simple answer.

    You're just lucky it didn't happen to be one there was much disagreement on. Then you'd really see some detail, not to mention the cut-throat, knock down, drag out debate.

  • rockfordchris

    I'm still doing my reading on lawns, came across this thread after earlier reading some papers from the local university, who say for my area light and frequent are best for Michigan lawn

    'Light, frequent applications of water are
    much more productive than heavy applications once a
    week. Remember that turf roots are naturally shorter
    during hot and dry weather, and water moved past the
    root zone is of no benefit. Research at Michigan State
    University also indicates that damage from certain turf
    diseases and insects is reduced when light, frequent
    (daily) irrigation is used rather than heavy, infrequent
    watering. That corresponds to 0.1 to 0.2 inch of water.'

    http://www.turf.msu.edu/docs/E0009TURF.pdf

    Just thought I'd share to the 'everyone is different' rule :)

    Here is a link that might be useful: Michigan State University Turf

  • marsyas

    SO... I did the can test on my popup sprinklers, I ran them for 10 minutes and got an average of 1.25" that seems like a lot of water for just 10 minutes. I placed 10 cans in random places, the ones closer to the head got almost 2.5" in 10 minutes. Any of this seem weird??

  • dchall_san_antonio

    Wow, there are some old names on this thread.

    Do you have a lot of overlap among the sprinklers? I have heard of 20 minutes to fill the can but not 10. Mine takes 8 hours for an oscillator type set on full sweep.

  • j4c11

    No, it can happen. I remember we had someone else last year with the same thing, but she had a very small lawn and a lot of sprinkler overlap. The problem is, can your soil absorb 1" of water in 10 minutes or are you seeing a lot of runoff?

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