RPZ Minimizing Pressure Loss

Discussion in 'Irrigation' started by dypsisdean, Sep 4, 2010.

  1. justgeorge

    justgeorge LawnSite Senior Member
    Posts: 352

    I haven't read all the pages of this thread, but you pick up 43 lbs of pressure with a 100 foot elevation drop. That should more than negate the 10 lbs you lose thru the RPZ. As others have said, all RPZs are going to cost you the same pressure loss so just install it and if you can't live with that pressure loss put in smaller nozzles. Even if you only started with 40lbs, losing 10 lbs then picking up 43 lbs 73 lbs is plenty for any system.
     
  2. Mike Leary

    Mike Leary LawnSite Fanatic
    Posts: 21,896

    :hammerhead::hammerhead::hammerhead:
     
  3. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,297

    The question was about pressure loss in water meters and RPZs ~ Elevation has absolutely nothing whatsoever to do with pressure losses in plumbing devices. Try to remember that little morsel of knowledge.

    And buy an %^&*%$# pressure gauge already!
     
  4. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,308

    And that would be the reason why you are faced with problems now.

    Pressure and flow are not irrelevant, and the fact you even make this statement is only an indication of your lack of knowledge in this field.

    This is categorically untrue.

    No offense dude, but I don't think you fully appreciate just how complex designing and managing irrigation can get. But then, why would I expect you would understand when your only concern is getting stuff wet without blowing apart fittings.

    What I still can't understand is why you think thin wall PE pipe and fittings can only handle 10-30 PSI? You completely disregard potential damage due to high flow, yet you hold onto this absurd idea that because thin wall PE pipe is primarily used with drip/micro it can only handle 10-30 PSI. FYI, as I said before, all the thin wall PE pipe and compression fittings I have installed over the years are all rated at 50-60 PSI max recommended operating pressure ... and I have run these at pressures approaching 50 PSI, and probably in some cases exceeding 50 PSI without any problems.

    Why do you keep harping on this elevation difference? The hydraulic head is what it is ... be it 10 feet or 1000 ft. FYI, there are far better ways to deal with it than your cobbled together home owner solution.

    Also, with the correct data, anything can be calculated to a very precise value. You get junk solutions when you feed equations junk data. It boggles the mind that someone with a physics degree doesn't understand this.

    What equations did you look at? We already know you don't haven't collected any reliable data .... so how exactly would you even use these supposed equations without any data, let alone quality data?
     
  5. dypsisdean

    dypsisdean LawnSite Member
    from Hawaii
    Posts: 38



    Sorry, I didn't realize the ability to type quickly would also be criticized here. But if you're a slow reader, I understand.

    And apparently you are unfamiliar with Driscopipe Series 8600 (my main supply line as explained earlier). The walls are 1/4" thick, UV won't touch it, you can run chemicals through it, you fuse sections together if need be, and it's preferred use is in earthquake and volcano fault zones, and other high impact demanding applications. It would laugh at a high flow rate.
     
  6. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,297

    With a 3/4-inch meter, a 1-1/4-inch mainline is not going to be troubled by excess flow.

    As far as the zone plumbing goes, screw it and the boat it floated in on. If genuine poly tubing that works with clamped insert fittings can't be had, there is the possibility of finding UV-R PVC pipe, that laughs (Ha-ha!) at sunlight.
     
  7. dypsisdean

    dypsisdean LawnSite Member
    from Hawaii
    Posts: 38

    I give up. If you don't read the detail, how can I continue.

    Once again - the fittings where the pipe is inserted into (not over a barbed end) are rated at 10-30psi. These are the only ones that do not restrict the full one inch flow.

    And you are just plain wrong about calculating "feet of head." It is directly calculated from distance, number and types of fittings, size of pipe, and the number of feet of rise or fall. In fact that is where the term "feet of head" comes from. Meaning the combined potential resistance to moving water through a piped system. I have no idea what you mean by "hydraulic head."

    Like I said, if you can't appreciate the fact that it's harder to push water uphill than it is downhill, I give up.

    And I'll try this one last time:
    There was only one type of pipe/tubing available for my application. There was only one type of fitting available to provide full inch flow. There was only one meter and one supply line available. And there was one objective - max overhead coverage per zone.

    So after I selected what I determined to be the best and most versatile sprinkler available, I just needed to start covering the acreage, zone by zone - adding heads to each zone until the performance dropped to an unacceptable level. Some zones took 13 heads, some took 15, and some took as many as 17 if they were closer to the valves and all downhill. Is that hard to understand? That method, by nature, yielded the optimum efficiency per zone given what I had available to work with.

    Really the only options or choices I had was different fittings, but I determined the extra flow was more valuable than the extra pressure. Or a different sprinkler. But I am very happy with the low pressure performance and versatility of the one I chose.
     
  8. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,297

    Barbed fittings do not restrict flow. This is a common misconception. Fittings, in general, do not restrict flow. They do have a pressure loss, however, and said loss is expressed in feet of equivalent pipe. So, an insert coupling might be equivalent to 2 or 3 extra feet of poly tubing.

    Now, in the entirely irrelevant world of swimming pools, pressure losses have meaning, because the pumps being used are limited in the amount of pressure they can produce, so losses have to be minimized for best operation.

    In sprinkler plumbing, pressure loss is just a number, and not a restriction of flow.
     
  9. dypsisdean

    dypsisdean LawnSite Member
    from Hawaii
    Posts: 38

    Thanks again for your feedback Wet Boots. Despite a few of your less than tactful comments, ;) I can tell you know what you are talking about.

    So let me explain something since you would probably appreciate the full story in an attempt to bring this thread to a close.

    I could have used 1" Driscopipe for my above ground application. It would have tolerated a few hundred psi, and would still be here and working a couple of hundred years from now since any fittings used are brass. However, the price would have been as much as 10 times more (probably 15) than what I paid.

    I used the flimsy pipe and fittings, choice of sprinklers, valves and positioning, tall riser setup, etc. as an experimental platform, and a way to keep things watered on one planted acre for several months at a time while I worked on retiring and moving here full time from California. I figured if the basic principle proved workable and adequate, I could eventually swap out and use the Driscopipe where the thin walled poly was for a permanent installation.

    However, it has worked so well, and for so long, I did the remaining 2 acres using the same technique. $500 beats $5,000 any day. But with the added acreage, increasing cost of water, and the 50 year drought, the water dept recommended I apply for ag rates. This is an ag community, and I am engaged in agriculture. Hence the origination of the problem you have been trying to help with.

    So, as mentioned earlier, with two stations vacant and available, and with easy access to the polytubing to re-route, and with the ability to play with nozzles, I should be able to make something work. If not, then I will admit i will need to put pencil to paper and work the equations to determine if a new meter would be worth it. If not, then I can always remove the RPZ on my own, sell it, and I'm back where I started, with a system that is doing what it was designed to do - and praying for rain. :)
     
  10. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,308

    I know what a compression fitting is bub. What part of I've installed thousands of compression fittings and run them at pressures around 50 PSI did you not understand? :hammerhead: But why don't you go ahead and explain to me why manufacturers would produce a fitting that is intended to be used with PE pipe rated at pressures around 50-60 PSI, yet can only handle 10-30 PSI? Perhaps you would like to provide a link to these fittings ... or perhaps I can go dig a few out of my truck and take a pic of them for you. :dizzy:

    I am wrong? I don't remember stating how one goes about calculating total head .... would you care to provide the quote? Perhaps before you go accusing people of being wrong, you might want to check your information because you just described friction head and elevation head, not total hydraulic head.

    FYI, hydraulic head is a combination of friction, velocity, elevation, and pressure head when we are talking about water in a piping system.

    WOW! :laugh: You mean head doesn't have anything to do with pressure due to the height of water in reference to a datum?

    And that would be the reason for your confused statements. Look it up!

    Who said it isn't? Furthermore, your not pushing water uphill ... so what is the point of this comment? Time and time again you have stated 100 foot drop over 500 feet.

    And once again ... that just goes to show your lack of knowledge, not only in irrigation principles and practices, but in available products. Really ... a PGP was the most versatile option? :nono:

    No professional would EVER design a system like you did. Why do you continue to repeat yourself here? It is not going to change the fact the system was poorly designed.

    Once again ... you don't fully grasp basic irrigation principles ... but of course why would you listen to a professional .... right?
     

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