3/4" Sch 40 and 152psi at connection?

Discussion in 'Irrigation' started by turt, Jun 14, 2005.

  1. turt

    turt LawnSite Member
    Posts: 76

    I am getting ready to install a new irrigation system and have a question. I have a 1" meter (120ft from the house) with a 1" sch 40 line coming into the crawlspace. From there, it reduced to 3/4" sch 40 and supplied throughout the house via 3/4" copper. The 3/4" scd 40 has a pressure regulator installed right above where it was reduced from 1". The pressure is about 50 psi after the regulator. I have a large lawn, about 2 acres that I intend to irrigate. Right now I'm using hoses connected to the hose bibs and can only run about 2 sprinklers at a time because the "measured" flow rate at the bib is around 10 gpm. I got the idea to tap into the 3/4" scd 40 before the pressure regulator for my sprinkler system. I ran this through a control valve and stubbed it outside above ground (temp until system is installed). There I connected a spliter and connected 5 above ground sprinkers with garden hoses. It seems to run all of them fine with good pressure. I did a flow rate test on this line and calculated 20 gpm. I was suprised by BIG increase but happy. I did not want to have to run 14 ZONES! Now I should be able to run 7 zones (4-5 RB 5004 per zone) with adequate pressure and flow. I was all happy until I tested the "pressure" of through this type of setup. It is 152 psi! I still think though that putting the 5 heads on one line and running all 3/4" sch 40 should be ok. I seems to be doing fine above ground through cheap garden hoses. The pressure of this setup when all heads are spraying is only 40psi. So I ask - Am I headed for disaster or what? First time trying to do this. Turt
     
  2. turt

    turt LawnSite Member
    Posts: 76

    I know there are a lot of smart guys out there on the subject. Someone please let me know if I'm about to wastes a lot of time and money.

    :blob3:
     
  3. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,026

    Install a pressure regulator on this new connection, and set it for about 100 psi. Not all regulators can adjust that high. A Wilkins BR-4 can. More accurate than connecting hoses and sprinkler heads is a pressure gauge and a water meter reading for gpm (or cfm with a 7.5 factor)
     
  4. turt

    turt LawnSite Member
    Posts: 76

    I did put a pressure gage on it and it read 152 psi. after I connected the hoses and sprinklers and had them running, the gage read 40 psi.

    If I reduce the pressure with a regulator to 100 psi. Will that NOT reduce the amount of sprinkler heads I can connect successfully? I want to be able to run 5 RB5004 heads. So, if I reduce the pressure, should I connect to the 1" pipe and run all 1" pipe for my underground system? I'm asking all these questions because I have 400ft of 3/4" pipe and I'm ready to start. I just want to do it right the first time - so I'm asking before I break out the shovel.

    Here's what I have done so far. I leveled, planted, seeded, strawed all myself and yes it is my first time to try this and it's a pretty large scale effort.

    http://www.kurtnsue.com/images/Houseconstruction/day87.htm
     
  5. turt

    turt LawnSite Member
    Posts: 76

    oops - Typo " I WANT TO DO IT RIGHT THE FIRST TIME"
     
  6. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,026

    You regulate the pressure so the lawn sprinkler equipment won't blow apart. I picked 100 psi as a set point, because an installation with poly pipe will not want to see more than 100 psi. The actual sprinkler head maximum psi is closer to 75 psi, but losses through the regulator, and backflow preventer and zone valves should get you to there. Do the plumbing correctly, then worry about how much water it's delivering.

    With two acres to water, you should be connecting at the one inch pipe and staying with one inch pipe (or even going up to inch and a quarter)

    150 psi is the maximum pressure rating of many backflow preventors and sprinkler zone valves, so operating without a pressure reducer is risky. A one inch BR-4 at your point of connection will pass enough water to run a dozen standard rotors. There will be a significant pressure loss involved, but if you start with 152 psi, you can afford a pressure loss.

    Doing the plumbing first, and measuring the flow and pressure afterwards, is a luxury you can enjoy as a do-it-yourselfer.
     
  7. turt

    turt LawnSite Member
    Posts: 76

    Thanks Wet Boots! I really appreciate the advice. I guess ripping out the two valves and some of the pipe in the crawl space and redoing it all in 1" will be worth it in the end. A lot easier to do it now then to have to dig up 2 acres of 3/4" and replace it all later. That's what I thought I should do but wanted to be sure. It chaps my butt that the plumber necked it down to 3/4" prior to going to a shut off valve in my utility closet in the laundry room. I had two shut off valves installed in the wall there. One cuts off the water to the whole house and the other was to serve as a cut off for a "future" sprinkler system. They were both done in 3/4". I can install a 1" cutoff in the crawl space, I'll just have to disable the line going up into the laudry room and do without the convienence of having the sprinkler cutoff in the laundry room closet. This is the same plumber that necked the hot side 3/4" copper down to 1/2" for 10ft then back up to 3/4" BEFORE it went to the rest of the house plumbing. Now the hot water has 1/2 the pressure as the cold water. I still cannot convience him that this is a problem. Professionals..... it's amazing I was able to get the house done at all. Time to break out the torch and fix his hot water mess.
     
  8. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,026

    If that water meter is located near the street, you have another option. If you tee off as close as is practical to that meter, your available flow will be at a maximum, maybe even more than the 50 gpm that a one-inch water meter is rated for. I would still run the supply through a one-inch pressure reducer, partially as to act as a 'brake' for flows approaching the 50 gpm limit, but once you are through that, you can go way up in pipe size, possibly to a 2 inch mainline, since it looks like it has to wrap around the house to get to the other side of the driveway. At over 30 gpm, you would use 1½ inch zone valves. Running a dozen heads at once (make it fifteen, maybe) would be nice for a property of that size.
     
  9. turt

    turt LawnSite Member
    Posts: 76

    Actually, I have 3" pvc conduit under the driveway near the street and just before the parking pad. :) I was thinking ahead (unlike my contractor)

    So using a 1" pressure regulator and then up-ing to 2"? did not know I should size up. I have a 1" line from the meter at the street "straight" to the crawlspace (where I want to install all my valves). About 120ft straight run from the street. Here is where I would want to put the 100psi regulator and start connecting my valves. From the crawl space, I can then run straight out to every zone (like the hub of a bicycle). If I did this, should I stay with 1" all the way, or would you still suggest upsizing the pipe after the regulator in the crawl space? How does running 120ft in 1" before upsizing affect it? Also, with what I have discribed, would you still recommend 2" and not 1". 1 1/4" or 1 1/2"? 1" valves and pipe would be easier on me and my budget if it will be effective.
     
  10. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    The math gets funny here, wetboots has given excellent advice. As to using larger pipe, do a little project math and realize how much less pipe, wire, valves and boxes you need if you upgrade to a 2" main and 1.5" valves. You should be able to use one 1.5" valve instead of 3 or maybe even 4 1" valves. The install becomes "cleaner", and you have less things to worry about. Another question would be what do you have available to purchase these supplies from? Is there a reputable sprinkler supply selling to home owners in your area? If you have that, consider upscaling your heads as well as your valves. You have the pressure and ability to run 60+ radius heads w/ that kind of pressure and volume. Now you are spending more per head and per valve, but you are drastically reducing the numbers. Just a thought. 60' heads would be Hunter I-25's (very reliable commercial head) or the RB Falcon or 7005's (again reliable quality products). Your 1.5" valves are also going to be more tollerant of the high pressure. RB PEB's are rated up to 200psi. Your still going to want to regulate your pressure BEFORE the backflow, and a backflow large enough to handle the flow you want will be important. Backflow devices are very hard on pressure when you max flow through them. Pressure drop is not as big an issue if you upsize the backflow.
     

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