Gpm

Discussion in 'Irrigation' started by TPnTX, Jul 31, 2006.

  1. TPnTX

    TPnTX LawnSite Bronze Member
    Posts: 1,776

    This is too funny. I'm going through the online tutorial for designing irrigation. Sorry I'm not a irrigation scientist like you guys.

    So one of the steps is to call the utilities company and ask them what the GPM is at the meter. It says they get asked that all the time. Yeah Right!

    I've got two locations, one is in the City(small town). So I call the City and they don't know what I'm taking about.

    The 2nd is a co-op water supply..."Yhew wont whut?"
    I said ....thanks have a nice day...f'n hick.

    So got a bucket and calibrated it. lol, well i did.

    The one house has PSI of 45. Right where the line comes into the house there is a spigot. I used it and it took 35secs to fill 5 gals.

    The other house had 70PSI and it took 30secs.

    So anyway for once in my A.D.D. life I try to follow directions and look where it got me.

    The other thing on this tutorial that I'm haveing trouble getting my arms around is the Double Check Valve. You know that isn't real clear. He contradicts himself several times. I do know better than to NOT use one. Although the one house "out of city" I could get away with just a back flow preventor.
     
  2. HooKooDooKu

    HooKooDooKu LawnSite Member
    Posts: 70

    It sounds like we're talking about www.irrigationtutorials.com

    There's a lot of information out there, and I must admit that there's just so much to it that it can really get confusing.

    But from my point of view as an engineer, everything said makes logical and scientific sence to me. Now my area of study was electrical engineering (hence the reason why I needed instructions to learn about plumbing). But cut the guy a break, as he indicates, he's an engineer, and we're pretty notorius for not doing well with writing skills.

    On the subject of the Double Check Valve, let me see if I can add anything that will help clear things up....

    The only difference between a Double Check Valve and a Double Check Backflow Preventer are the test cocks. The test cocks allow each Check Valve of the Backflow Preventer to be tested independantly and therefore prove the device is fully functional. If you only install a Double Check Valve, you have no way of proving that Check #1 is working and Check #2 is working. The most you could do is hook something up that would attempt to push water backwards through the Double Check Valve and prove only that "at least one check valve is properly working". However, if you have a Double Check Value Backflow Preventer, you can test Valve #1 for backflow protection and then test Valve #2 for backflow protection.

    Hope that helps clear things up a bit.

    If you only install a Double Check Value, you have to way to prove that each check valve is working properly. Even if took the time to add our own external test valves around the Double Check Valve, you can't prove that each Even if you add on your own external test connections, the only thing you can prove is that "both checks are currently on failing", you can not prove that each check valve is
     
  3. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,799

    Double checks always have the testcocks, the valve without testcocks is called a "Dual Check". I can't think of any area that will allow a dual check as a backflow preventer.

    Doublecheck:

    [​IMG]

    Dual Check:

    [​IMG]

    Notice how the dual check has no shutoff ball valves, or testcocks.

    That said, check your texas requirements for backflow, I'm pretty sure you need a plumber to instally your backflow for you there, and I wouldn't be surprised if they require a PVB or a RPZ.
     
  4. TPnTX

    TPnTX LawnSite Bronze Member
    Posts: 1,776

    I got all that. Where he lost me was here:
    [My recommendation:
    I do not recommend the use of double check backflow preventers on irrigation systems. I do not use double check backflow preventers on my projects except in very rare cases where I am either required to, or special conditions exist such as sprinklers mounted very high above the ground where contaminates can't reach them. There is a very simple reason for this. I am a registered Landscape Architect, and as such I am required above all else to "protect the health, safety, and welfare of the public". Thus I am held to a higher standard than a homeowner or other non-licensed person and my advise must reflect that. So if you write and ask me if I would recommend using a double check, even if you think you have a special circumstance that eliminates ALL of the risk, I am still going to tell you no. Because that is what I have to tell you!
    ]

    1st there is this line

    except in very rare cases where I am either required to, or special conditions exist such as sprinklers mounted very high above the ground where contaminates can't reach them.


    Okay rare cases? aren't you always required to use one.
    and..sprinklers mounted high would be a resaon one is not needed.

    and this line:
    [I am a registered Landscape Architect, and as such I am required above all else to "protect the health, safety, and welfare of the public". Thus I am held to a higher standard than a homeowner or other non-licensed person and my advise must reflect that]

    Dang it Jim I'm a doctor! I mean come ON...either its a good thing or a bad thing. Make up your mind. Better yet I don't care just keep tutoring and get off the soap box.

    and finaly this
    [So if you write and ask me if I would recommend using a double check, even if you think you have a special circumstance that eliminates ALL of the risk, I am still going to tell you no. Because that is what I have to tell you!]

    soooo. thats a no or a yes-no. It's like the sign says "No U turn" so okay then I'll turn....
     
  5. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,799

    There is more than one form of Backflow protection. What Jesse Stryker is trying to say is that he wouldn't use Doublecheck as his backflow protector unless forced to.

    Other options are Pressure Vaccum Breakers, which are popular, and RPZ's.

    Both of those devices must be mounted above ground, while a Doublecheck can be buried.

    Those two devices are also considered "superior" because they vent their backflow out, but I'm in Doublecheck land, so doublechecks go in here.

    Jesse is not advocating not using any backflow at all.
     
  6. PurpHaze

    PurpHaze LawnSite Fanatic
    Posts: 5,496

    You MUST take that site with a grain of salt and your mileage may vary. :)
     
  7. WetWell

    WetWell LawnSite Member
    Posts: 59

    You might want to check on the size of that bucket unless it is labeled, there are a lot of buckets that look like 5 gallon for example but hold more water and also some that are only 4 gallon floating around.
     
  8. TPnTX

    TPnTX LawnSite Bronze Member
    Posts: 1,776

    like I said...I calibrated...ah never mind.
     
  9. HooKooDooKu

    HooKooDooKu LawnSite Member
    Posts: 70

    TPnTX,
    Like I said, Jesse has a lot to say, it's all technical in nature, and he's writing it as an engineer. So some of it is bound to be confusing. It took me several attempts at reading and "getting my hands dirty" doing so work on my own system before I (as an engineer) got to "get it" my self.

    But like I also said, I can't find any fault in anything Jesse has to say on his site. The only truth I can find in comments like "take that site with a grain of salt" is the fact that Jesse is a bit over-protective. But then again, he pretty much says that in the stuff you most recently quoted... "I am held to a higher standard than a homeowner". So there's many times when Jesse is advocating something that might not be done in practice.

    The Filter Example:
    A great example of Jesse being over-protective would be on the subject of filters. I'm under the impression that most professionals on this board do not install seperate filtration on the typical system install. Jesse, however, always recomends seperate filtration, even for a regular irrigation system connected to city water. I'm guessing that the truth is that a filter does improve the reliability of a system and can reduce the maintainece for a DIY homeowenr. But for a professional, a filter on every install creates another routine maintenance without solving enough problems to justify (i.e. it's eaier for the professional to just fix problems caused by NOT filtering than it is to maintain hundreds of filters).

    Now at the same time, I got to admit that I ran into a few issues with Jesse's stuff and I had to ask him for some clarifications. An example of this was when I pointed out that www.irrigationtutorials.com calls for PVC mainlines to only be used when the pipe is burried 18". But his drawing show PVC leading to control valves where the pipe is obviously not burried by 18" of soil. So I guess there are a few things to "take with a grain of salt".
     

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