Expert: James Grote - 8/30/2006

Question
Jim, thanks for the quick reply.  Ok, so I want to use 1 1/2" pipe the whole way, correct?  This means I should use 1 1/2" globe valves as well?
What about the pressure reducer and the backflwo preventer, do they make them with 1 1/2" inlets/outlets?

Yes, I will place the pressure reducer before the backflow preventer. I know it is hard to believe my pressure is so high...but I have had it checked by several people and they are amazed too....   

Should I stick with just two sprinkler heads on a valve or increase that to 3?  I also will space my heads closer together. I just want to water the pastures enough to keep the dust down for both the horses and the neighbors.  So I will proabbly only run the system, for 8-10 minutes, 2-3 times a day, depending on the heat factor.  I live is Southern California, so it is not too awfully hot.

Ok, thanks again for the info and if you have time to answer these quetions I have just asked, I would greatly appreciate it.
Thanks Deborah

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Followup To

Question -
My water meter is 3/4 and my supply line is 1 1/2".

I have three large pastures (140' x 90' and the other 2 are varied in size-much larger).  All pastures slope downward and are below my water meter.

I need to know if the following information that I have been told about my design is true?

I have been told to use 1 1/4" PVC sch. 40.  I have, believe it or not, PSI of 190, so I will be installing a pressure regulator and droping that down to about 80-85 psi.   I also will install a Reduced Pressure Backflow Preventer, so that I can use 1" globe valves (or should I use 1 1/4" or 2" globe valves?) throughout the system.  

I would like to know what brand of valves to use for the Presure regulator (200 PSI), the RPBP, the globe valves and the sprinkler heads.  I was told to use Toro Sprinkler heads 2001 series used for golf courses, being that my pastures are deep and they can spray up to 75'.  I am placing them at about 50'intervals.  

I am only placing two sprinkler heads on one valve?  I hope this is correct?

Can I run the 1 1/4" pipe right up to the sprinkler heads (that will be attached to my fence posts) then use a bushing to accomodate a 1" female opening on the sprinkler itself?  Or should I run a 1" pipe off the supply line through the globe valve then up to the sprinkler?

Any suggestions and help would be greatly appreciated.  I hope I have made sense of my questions?

Answer -
Deb,
Lot of questions here. I'm earning my money on this one. First of all, lets look at the water pressure. If it is in fact 190 PSI, (and that is the highest I've ever heard of), then you will need to put pressure regulator BEFORE the Backflow preventer because as far as I know the maximum operating pressure of most RP's is 175 PSI. There may be a particular make and model that goes above that, but I don't think so and there wear and tear on the springs and rubber seats in the backflow at 190 PSI would cause a lot of problems immediately.

Now, to get teh distance of 75 feet you are going to be putting nozzles in the heads that put out 35-45 gallons per minute. With 2 heads on a zone you are looking at 70-90 gallons per minute. sounds like a lot of water and it is. The gallons per minute (and pressure) determine pipe sizing.
The one problem I see here is that it doesn't look like you can get that many Gallons per Minute through your 3/4" meter. OK, I looked up the 2001 head and the longer radius is 71 Feet. So you're a little short of the 75 feet, but no big deal. To get the farthest radius you put a 30 Gallon nozzles, you have 60 gallons per minute there. According to my cacilations, there is now way you will get more than 30 gallons per minute, maybe 40 gallons a minute through a 3/4" meter. Even a 1" meter is stretching it, but may work with the extra pressure. So the high pressure will increase the flow and maybe get a 1" meter to flow that much water. The other thing with pipe sizing is you have to look at the Feet Per Second of the water. The guys who make PVC pipe  have charts and they like to keep the speed of the water under 5 feet per second. The gallonage is so high that you get 18 feet per second.

So you could take less distance , like 50 ft. radius , and thats will knock down the gallons per minute to as low as 9.4 gpm with the #6 nozzle in the 2001 head to about to under 20 gallons per minute with the #12 nozzle. Which would mean you could keep the meter and space the heads closer.

I also suggest 1 1/2" pipe to the head are at least 1 1/2" pipe out of an 1 1/2" valve and then telescope down to the smaller pipe at a tee or something.

I don't know if I answered all your questions sufficiently. Watts make most of the pressure regulators and they make a good one.
  Let me know if you need more info. Jim

Answer
  
  Deb,
As far as the number of heads go, I guess I was not clear, but you can not pump more than 2 of those big heads and get the distance you want with due to the size of the existing meter you are planning on connenting to.  2 heads is the max-no matter how high thew pressure is. You can only push so much water through a 3/4" pipe. I did not know that you are using the sprinkler for dust suppression so spacing can be a little stretched,  about 55 feet. Again, this is due to the size of the meter and you can't get the flow to pump the 2 heads 75'.



The ressure reg. comes in 1 1/2" that's a common pipe size. 1 1/2" backflows also common.

The pipe size should be 1 1/2" to the point where the piping splits off and goes to each head, where it could be dropped down to 1 1/4". The price difference between the sizes is minimal, so 1 1/2" keeps it simple.

And yes, use 1 1/2" globe or angle valves.


  jim