# New Irrigation Design -- Confusing GPM Selections



## psider25 (May 4, 2020)

Hi, I am looking for some feedback on my irrigation design for my front and side yards reno. I'm having a hard time validating the different GPM per head and total number head per zone.

Below is the drawing that came back from the design service.

I have 3/4" copper coming from the water supply. It converts to 1 inch copper just before the backflow preventer. The water meter is 5/8". I calculated just under 10 GPM for max flow which agrees with theoretical values for 3/4" copper and 5/8" meter.

I have 68 psi static pressure.

I plan to swap out all the residential heads that rain bird choose (ie 42sa, 32sa) for 5004 Rotors (likely with check valves and maybe 45 psi pressure regulator to make the system pipe design more idiot proof).

I am a little bit worried about all the low flow nozzles chosen, so wondering if others recommend bumping them up but then having to have more zones? or make other design changes?


----------



## psider25 (May 4, 2020)

The scale is each square is 5 ft x 5 ft ... so 150 ft across the bottom of the property


----------



## psider25 (May 4, 2020)

Has anyone ever followed the free Rain Bird homeowner design service design and had good (or bad) results???


----------



## g-man (Jun 15, 2017)

This layout is a good start. There are a few odd spots. In the right side there is a small rectangle there. They placed two heads, but I think this area will be trouble in the future.


----------



## psider25 (May 4, 2020)

@g-man thanks for the reply.

Are you concerned about the red, purple, or green circle below?

Also, do you have experience with rain bird 5004? My plan is to switch out all the 42sa and 32sa residential heads to 5004 heads. Does that sound like a good idea to you?

In order to get more heads on a zone with my low GPM they used smaller nozzles. Do you have any concerns with using 1 and 2 gpm nozzles?

Thanks again. I'm excited to start getting pipe in the ground.


----------



## g-man (Jun 15, 2017)

Green.

Lower gpm might mean lower precipitation rate, and that's a good thing.

I don't know much about rainbird product lines.


----------



## TSGarp007 (May 22, 2018)

I have a couple Rainbird 5000 series (the six inch version). They work great for me. I also have Hunter I-20 nozzles, they also work really well. I-20s can be shut off at the sprinkler which is really convenient when adjusting a zone so you don't get soaked, but adjusting one side of the stop is a little more difficult. Check the nozzle lists for the 5000s, make sure your options will work. I don't think you can get a 1.0 nozzle unless it's low angle, which isn't the best.

Are you doing this yourself? If so, it won't cost much more to just add a couple more zones if you want more gpm per sprinkler, or the ability to add a sprinkler later if needed. An irrigation company may have charge by zone method that would raise the cost more than just the extra valve and some PVC.


----------



## psider25 (May 4, 2020)

@TSGarp007 thanks for the reply

I am doing this myself... hoping to rent the trencher this weekend if weather cooperates and I get enough confidence in my design. The 5004 Rainbird is supposed to have this feature of shutting them off at the head as well.

I guess the smart thing to do would be to add more zones to allow for more flex later ....I just didn't want to have so many and make it take forever to water the yard. Well ...and to also make it easier for me to install 

What is the shortest distance you have your rainbird 5000 rotors set to water?

I have been trying to verify the design by rule of thumb that if I have a rotor spraying 360 degrees then the rotors spraying 180 degrees would be half the GPM as the 360 degree rotor and the 90 deg spray rotors would be half the GPM of the 180 degree rotor to keep precip rates even. Since I only have 9-10 GPM to play with I can't really put the 360 deg rotors on at 6 GPM, but I am very new to this design process.

The other thing I don't understand yet how to calculate is that if I go light on the number of heads per zone and don't use all the available GPM will I run into a velocity issues where the speed of water in the pipe is more than 5 ft/sec and could cause issues down the road. ie What happens for example if I only installed one head on a zone that used a 3 GPM nozzle? would that cause velocity issues in the system?

Here was a quick and dirty guide I found on irrigationtutorials.com, but I will not be able to follow it exactly. They say to avoid using rotor nozzles less than 2.5 GPM except in corners, but not sure I totally agree.


----------



## psider25 (May 4, 2020)

sorry here is the quick and dirty guide....

For 20-29′ spacing between sprinklers-
1/4 circle . . . 30 PSI - 0.8 GPM
1/2 circle . . . 30 PSI - 1.6 GPM
3/4 circle . . . 30 PSI - 2.4 GPM
full circle . . 30 PSI - 3.2 GPM

For 30-39′ spacing between sprinklers-
1/4 circle . . . 40 PSI - 1.5 GPM
1/2 circle . . . 40 PSI - 3.0 GPM
3/4 circle . . . 40 PSI - 4.5 GPM
full circle . . 40 PSI - 6.0 GPM

For 40-55′ spacing between sprinklers-
1/4 circle . . .55 PSI - 3.0 GPM
1/2 circle . . . 55 PSI - 5.5 GPM
3/4 circle . . . 55 PSI - 8.0 GPM
full circle . . 55 PSI - 11.0 GPM


----------



## TSGarp007 (May 22, 2018)

I think my shortest 5000 is maybe 27'? Kind of a guess, sorry...

It doesn't matter if you use all your available gpm or not, the 5 ft/sec rule only depends on how much water is running though the pipe. If your sprinkler uses 3 gpm then that's all that will flow through the pipe (assuming normal pressure).

The quick and dirty guide you referenced makes sense. Larger radius throw nozzles usually require more gpm I think.

Take any of g-man's advice over mine... just a homeowner with limited diy experience here.


----------



## g-man (Jun 15, 2017)

Trench this weekend? I think it is important to have a robust plan. The layout they gave you is a good start, but I would go thru irrigation tutorials and make sure the details are clear (gpm, nozzles, heads, pressure losses, pipe sizes).


----------



## bernstem (Jan 16, 2018)

More zones won't let you water any faster or slower if you are using all your GPM. If you double the number of zones making them half as big, you will cut in half the amount of time they need to run since each head will be flowing twice as much water. Net result is twice as many zones running half as long and the same total irrigation time. You are ultimately limited by your total GPM.

If all your sprinklers have the same throw (or close to it), then nozzle sizing is easy. the ratio is 4:3:2:1 for 360:270:180:90. If your 90 is a 2GPM nozzle, then the 180 would be 4GPM and the 360 would be 8 GPM.

If you have different radiuses set on the same 5005 heads, then it gets more complicated since the flow is the same when you reduce the radius on the 5005s, but the total area is lower. You also affect the water distribution and can get dry spots from it so you should try not to reduce radius on rotor heads like the 5005s if you can help it. If you do reduce radius slightly, I would still use the same ratios, and accept that it will be a bit off. If you use Rotator heads (MP rotators or R-Vans) you can change radius without the problems of rotors like the 5005s since the precipitation rate stays the same regardless of radius or throw distance.


----------



## psider25 (May 4, 2020)

@Gman107 
@TSGarp007 
@bernstem

Thanks for your feedback.

I have redesigned the design above as below. Reduced number of zones and increased GPM for individual heads. I will run all Rainbird 5004 heads. To make it idiot proof (slightly) i may put in 45 psi pressure regulators in each head. There will be no drains.... a complete blow out system. Also you can get check valves inserted in each head for a couple bucks extra.

Looking at rachio 3 12 zone controller from Costco.

The current plan is to run 1.25 inch mains and 1 inch laterals.

The backyard is not in scope here for this reno as I will be changing the layout of backyard in 2021 and then add to the system at that time.


----------



## bernstem (Jan 16, 2018)

I think the bottom dark blue should be 3 and 6 GPM heads. Aren't they 180 and 360 degree throw?


----------



## psider25 (May 4, 2020)

@bernstem

Thanks. I am designing to 9 GPM (theoretically I should get 10 GPM but wanted to be safe in an older house and neighborhood) and thought to keep it as one zone I could half the GPM for that zone completely all heads, but just have to water longer.

Do you think that will work?


----------



## bernstem (Jan 16, 2018)

Yes, you will need to run the zone twice as long, but it will work just fine.


----------



## Ge0rdi3brit (Aug 30, 2018)

Other option is to break your blue circle area into two zones (one 180 radius and one 360 radius each). Looks like all your other 180 sprinklers will have 3gpm nozzles, except one. Then you'd have a total of 7.5gpm per zone. Looks like you have plenty zone space if you're going with the 12 zone Rachio controller. 
As you mentioned, you need to keep in mind total watering duration and factor that into a watering schedule.


----------



## psider25 (May 4, 2020)

Does anyone have any feedback regarding whether I should change the design to do a Looped Main Line?

Has anyone seen real advantages of doing a looped mainline?

My focus is on the reno area now but I will be adding the backyard area in a year or two (at least 3-4 zones and 12+ heads)


----------



## TSGarp007 (May 22, 2018)

I don't think looping your mainline would be worth the effort. I have multiple valve locations and chose to use a master valve (got the idea from this forum), b/c I didn't want pressurized waterlines all the way around the house.

Assuming your yard is relatively flat, If I were you I would just regulate the pressure down to maybe 50 psi and just correctly size (or oversize) the pipes. That might be cheaper than getting the PRS option for each sprinkler. You're designing to 10 gpm max, so it should be pretty easy. I'd use 1.5" for the main, and either 1.25" or 1" for the laterals. 1.25" would be the overdesign and could probably handle 15 gpm should you actually be capable of it, but the 1" should give you 10 gpm easily with maybe only 1-2 psi drop on your longer runs at under 5 ft/sec.

I looked it up and yeah it looks like the '+' version of the 5000s have a shutoff feature. I don't think I have the '+' model.


----------



## psider25 (May 4, 2020)

@TSGarp007

Thanks for the input. Does your design on master valve mean you always open two valves at once during watering? Are there any down sides to this design besides cost? Did this allow you to not have to use schedule 40 PVC?


----------



## TSGarp007 (May 22, 2018)

Yes, there is a master valve that opens every time any of the zones are running. The additional cost is minimal since it's really just one more valve. Technically you could now use a pipe that says it is not for constant pressure, but I still used PVC for the master line. Only down side I can think of is that if the master valve fails then you've lost all your zones.


----------



## psider25 (May 4, 2020)

@TSGarp007

I just submitted my parts list to site1 for a quote.

The manager looked at the design and is recommending that I just use 1" inch PVC all around. Thinks 1.5 inch PVC for the main line will be very much overkill and even if I use 1" for everything I will be still between 45-55 psi at all heads. My static pressure at hose bib shows 68 psi.

My current backflow is a PVB which has ~5psi loss as opposed to a RPB which would have about 12 psi loss if that matters. Maybe I should design for having to switch to RPB in future ...but even with 12 psi loss I think I'll be fine.

Anyway this is what they quoted for pipe:
PVC Pipe 1 in. x 20 ft. SDR-21 (CL 200) Bell End

Actually here is the whole list:
1 PVC05C-030 Spears PVC-05 Clear PVC Cement Low VOC Medium Body 1 qt. 1 
2 PRIM70P-030 Spears PRIMER-70 Purple Primer Low VOC NSF 1 qt. 1 
3 SB5000 Blazing Switchblade PRO Quick Release Pipe Cutter 1-1/2 in. 1 
4 100DV Rain Bird DV Plastic Globe Valve 1 in. FIPT x FIPT 7 
5 D109-G NDS Standard Valve Box Round 6 in. Black Box/Green Lid Overlapping ICV 7 
6 436-010 Sch 40 PVC Male Adapter 1 in. MIPT x Socket 14 
7 BVS-1 Blazing SnapLoc Wire Connector Clear/Blue 25 
8 5004+PC Rain Bird 5004 Plus Part-Circle Rotor 4 in. Riser 30 
9 RB-SBE075-SPEC Rain Bird Spiral Barb Elbow 3/4 in. x 1/2 in. MIPT x Barb 50 
10 RB-SBE050-SPEC Rain Bird Spiral Barb Elbow 1/2 in. MIPT x Barb 50 
11 406-010 Sch 40 PVC 90 Degree Elbow 1 in. Socket 20 
12 401-010 Sch 40 PVC Tee 1 in. Socket 20 
13 429-010 Sch 40 PVC Coupling 1 in. Socket 5 
14 417-010 Sch 40 PVC 45 Degree Elbow 1 in. Socket 5 
15 402-130 Sch 40 PVC Reducing Tee 1 in. x 1/2 in. Socket x FIPT 20 
16 407-130 Sch 40 PVC 90 Degree Reducing Elbow 1 in. x 1/2 in. Socket x FIPT 20
17 1813HD500 Multi Conductor Wire Black 18 Gauge 13 Conductor 500 ft. (Sold per ft.) 500 
20 1PVC200BE PVC Pipe 1 in. x 20 ft. SDR-21 (CL 200) Bell End (Sold per ft.) 1,200 
21 FLEXSG Hunter FLEXSG Swing Pipe 1/2 in. x 100 ft. (Priced per ft.)


----------



## TSGarp007 (May 22, 2018)

I think that's a thinner walled pipe. It will handle the pressure just fine but can also handle more water flow because the outside diameter is the same with thinner walls. The schedule 40 is a tougher pipe in this size range. So your guy is correct. And I had it over designed bc I thought you wanted equal pressure everywhere


----------



## psider25 (May 4, 2020)

@TSGarp007 and anyone else who has used 5000 series rotors...

I have been double checking various design choices. Below is pasted the spec from Rainbird for radius (ft) and GPM for each available nozzle at 45 psi. I was hoping to use 100% the same heads throughout the design but have a range of throw distance needs that span ~25 ft to 40 ft. My current plan uses 1.5 2.0 and 3.0 GPM nozzles. Should I take below as "truth" ie expect the full range? or downgrade it a little.

My main concern is that I have a few heads where the throw distance is supposed to be only ~25 ft and that would be below the 25% reducability from the adjustment screw for radius. Do I need to drop down to the 3500 series rotors for those? If I drop some heads down to the 3500 series rotors can I mix 3500 and 5000 series in the same zone?

5000 Series Std. Angle Rain Curtain™ Nozzle Performance (at 45 psi)
NOZZLE	RADIUS FT.	FLOW GPM PRECIP IN/H PRECIP IN/H

1.5	35	1.54	0.24	0.28
2.0	37	2.07	0.29	0.34
2.5	37	2.51	0.35	0.41
3.0	40	3.09	0.37	0.43
4.0	42	4.01	0.44	0.51
5.0	45	5.09	0.48	0.56
6.0	46	6.01	0.55	0.63
8.0	47	8.03	0.70	0.81

Rain Bird 3500 Nozzle Performance (at 45 psi)
NOZZLE	RADIUS FT.	FLOW GPM PRECIP IN/H PRECIP IN/H

0.75	17	0.77	0.51	0.59
1.0	21	1.06	0.46	0.53
1.5	24	1.48	0.49	0.57
2.0	27	1.93	0.51	0.59
3.0	31	3.00	0.6	0.69
4.0	35	4.13	0.65	0.75

Thanks again for all the advice and input from everyone here.


----------



## TSGarp007 (May 22, 2018)

That's fine, just try to match the precip rates with nozzle selection (assuming equal head to head coverage). Keep in mind the precip rates for the 5000 will be higher than listed if you reduce the radius, so that issue is kind of there either way.

I would plan on getting a couple feet less than the advertised radius, kind of a safety margin.


----------



## psider25 (May 4, 2020)

Thanks.

Asked about the 3500's from the local supplier and the consensus around their shop is they (3500) are junk and the better option would be to use 5000's with low angle nozzles to reduce the radius to meet my needs.

I think I will just try his recommendation and see if it works. Either way it seems it won't change my head layout or how the zones are arranged ...I think. I really don't want to get everything installed and then have to move large sections of pipe ;(


----------



## JerseyGreens (Aug 30, 2019)

Stupid question alert - figured I post it here given the feedback on here.

Changing out nozzles and lost the adjustment screw - any idea what size they are and where I can buy them? THanks!


----------

