What is considered std practice for things like funny swing pipe?

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jdhughen

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I'm mapping and rebuilding a sprinkler system for property I recently purchased. The owner had passed a few years back and the widow didn't know anything about what had been installed. After getting the pump running again, locating all the valve boxes, supply lines, and control cabling, I started on the zones. the system is ten years old so I'm upgrading most of the in ground rotors as I go. Many of the rotors in shrub areas are elevated 18" to 30" on 3/4" PVC risers. I've noticed that funny pipe was used a lot for the jump from the 1" or 1 1/4" supply lines (it varies by zone) to the sprinkler heads. Risers are supported by being pipe clamped to 2-3' 3/8" rebar stakes in the ground. These are all 3 GPM rotors, a mix of Rainbird 5000, and Hunter PGP. Most funny pipe usage is within the 24" limit I read about but many are over, a couple as much as 8' coming off 1 1/4" zone supply line. Is this a issue and should it be replaced with PVC closer to the head?

Also how do you account for funny pipe pressure loss in zone calcs for overall pressure loss / requirements?

I've read that zone pressure readings should be take from the "last" sprinkler head ? I have a zone that the supply tees off into a kind of "H" configuration? Do I just used the head that has the furthest pipe run from the valve ?

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WorthFlorida

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I wouldn't worry about pipe type or pressures unless there is a zone or part of a zone not putting out water as needed or expected. If you're designing a system for a golf course, yes everything counts as the right type and size of pipe, etc. Just remember all you are doing is dump water on the ground and all the planning seems to always result with a dry spot or two, or too much puddling and run off. If you have a good pump putting out plenty of water, pressure's per zone is not critical nor helpful. Pipe diameter causes different pressure readings with steady pressure and flow rate from the pump. Look up the flow rate chart for your pump. Place a pressure gauge at the pump and with that reading you can estimate the water flow rate for each zone.

Generally pipe diameter starts out larger at the pump and step downs in size as you get to the sprinkler heads. You didn't state the size of irrigation zone area's but rotors come in 1/2" or 3/4" threaded connection. As you may know funny pipe barbs of 1/2" are 1/2" or 3/4" threaded connection. When it comes to rotors having some overlap of the spray pattern is for better coverage. Rotor sprinklers nozzles can be changed out for different flow rates and distance. You can buy rolls of funny pipe and occasionally going several feet like 8' or more in your case is not unusual. The bottom line is when the irrigation is running, does the coverage look good and as needed. If some sprinklers looking too short or too long in coverage, changing the sprinkler head or nozzle of a different flow is far easier than change to a different pipe size.

For irrigation planning you want the same sprinkler type for the entire zone but that is not always possible. Supporting risers with rebar is not unusual and I've use rebar myself especially with tall risers since the back pressure will lean over the riser. Using funny pipe at the last 2' or so is very common now and the preferred way. It allows for flex to place the sprinkler exactly where you want it. At one time PVC was right to the head with no flex. From been driven over by a vehicle next to the driveway or a heavy riding mower, the PVC would crack.

With todays water restrictions all around the country the direction in the industry is to minimize run off with low flow heads such as MP rotors. In Florida, even with a well, lake water or as I have now, reclaimed water, there still is water restrictions.
 
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jdhughen

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Thanks for the reply.

A little more detail. valves are a mix of brands but all are 1", All rotors and risers are 3/4", all funny pipe barbs thread ends are 3/4". Supply lines to the valve boxes are 1 1/2", supply lines within a zone are 1 1/4" until it goes to funny pipe. Static dead head pressure at the well head is 147 psi. Well head pressure with the largest zone on is 115 psi. There is a watts pressure regulator at the well head going into the main supply line (1 1/2") which it set at 45 psi. The largest zone is 11 3.0 GPM rotors so that doesn't leave much room for expansion under the limit of a 1" valve ? My wife is really into large groups of container ornamentals, To get better coverage for those I really need to add something (drip or localized spray) to that zone. I could easily reduce the volume of 4 of the rotors to 2 GPM and get more even watering amount. That would leave approx 10 GPM under the valve limit of 40, would that work ?

As far as getting better use of my pumps' capacity can you double up on zones ? the next largest zone uses 9 rotors @ 3 GPM each = 27 GPM . Even if I maxed out the zone above at 40 GPM adding this zone at 27 GPM = 67 GPM which is still under the pump capacity of 80 GPM . Can things be added that way ?
thanks

Joel
 

jdhughen

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With todays water restrictions all around the country the direction in the industry is to minimize run off with low flow heads such as NP rotors. In Florida, even with a well, lake water or as I have now, reclaimed water, there still is water restrictions.

So I assume if I uses MP Rotators I would have to add more heads to get the same coverage as the PGPs ?

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Joel
 

WorthFlorida

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It's no problem doubling up on zones but a 5HP pump is big time, way more than ever needed for most residential properties. It seems to me the previous owner went big for some reason. There are those who think more is always better and the pressure reducing valve was probably added since sprinkler heads (pop ups) might have been blowing off. From your other post, https://terrylove.com/forums/index.php?threads/sizing-prv-for-irrigation-well.99021/ , take the recommendation from Cary Austin on his Cyclic Stop Valve. I'll make your pump last longer and really give what you are looking for, steady pressure on all zones.

You might want to call up the company and ask if adding a small pressure tank and a CSV, if a garden hose can be used (only thing running) so the wife can hand water her garden areas or use drip irrigation.

Leave your current set up with rotors and pop-ups. If the rotors are throwing a lot of water, it will allow for shorter irrigation times. Look on the Hunter MP rotor charts. I was on it just yesterday and they have some good for 35 feet of coverage. I replaced my last three pop up with MP rotor's and I cannot get them to be less than 8 feet so I'm hitting the home next door. You do not want irrigation water constantly spraying on the painted stucco. I'm going to need strip spray pattern.
 
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