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Tuesday, June 27th 2006, 8:13pm

Off The Charts!!!

I have read a lot of this forum, but I still need help. I am planning to install a new sprinkler system in both front and rear yards. Both yards are rectangle in shape. I want to run Hunter I-20s in both. 6 rotors with low angle nozzles in front yard 29'- 55', 1 in each corner and 1 on each edge of 55' sides. 8 rotors with short radius nozzles in rear 22'- 68'. 1 in each corner and 2 along each 68' side. I was planning on using Rainbird 100-ASVF valves, 1" sch 40 on inlet side and 1" class 200 for rest of system. I have a 3/4" meter and 1" service line. The static pressure is 110 PSI. I am not sure how many valves to use or what size nozzles since there is no chart that lists 110 PSI on it. Can I run one zone in the front yard and one zone in the rear? Any help would be greatly appreciated!!!


Active Member

Posts: 7

Location: USA


Wednesday, June 28th 2006, 5:31am

I'm not trying to give you a short answer but go to and do alot reading and them you will know your answer.


Supreme Member


Wednesday, June 28th 2006, 5:47am

#1. As jabbo said, check out irrigationtutorials

#2. 110 PSI is TOO MUCH for an irrigation system. Just like your house has a pressure regulator to prevent that much pressure from damaging appliances inside your house, your irrigation system needs a pressure regulator to prevent damage to it's components.

What I think you'll discover reviewing irrigationtutorials is the recommendation that any system with an incomming pressure greater than 80 PSI needes a pressure regulator on it.


Tuesday, July 25th 2006, 3:18pm

Thanks for the reply guys,
I've been busy digging ditches. Anyway, I was reading the specs on the Rainbird 100-ASVF and it reads anything over 150 PSI will need a pressure regulator. Can't I just use the flow control on the valves. Or is it just best to regulate the incoming pressure. I did go to irrigation tutorials, but I was hoping to get the thoughts of the readers and users of this forum. I thought that was the whole purpose of SPRINLKER TALK, not pushing off inquiring and confused people to irrigation tutorials.


Supreme Member


Wednesday, July 26th 2006, 5:45am

While I too referenced the irrigation tutorials, I already gave you a direct answer already.

When the valve says use a regulator for pressures over 150psi, that's just means the valve is designed for a maximum pressure of 150psi. But the rest of your irrigation system is NOT going to handle 100+psi. As a specific example, the rainbird 1800 series popups specify a maximum input pressure of 75psi.

Now in theory, flow control can be used to reduce the pressure. But in practice, how are you going to implement it. You would have to have a way to connect a pressure gauge to each circuit so that you could adjust the pressure. And as conditions change, the pressure would change as well.

Inline pressure regulators you could install upstream of the manifold are available for about $10-20.


Supreme Member

Posts: 5,331

Location: Metro NYC


Wednesday, July 26th 2006, 9:44am

You can work with 110 psi static pressure, with the ASVF flow controls closed down to protect the zones from high pressure. Just know that most residential heads aren't supposed to see more than 75 psi.


Wednesday, July 26th 2006, 11:54am

Thanks for the quick replys. I guess I just think a little too much. I will just play it safe and make my connection after my pressure regulator going into the house. Thanks again!!!


Supreme Member


Thursday, July 27th 2006, 4:58am

[Edit: Disclaimer - Some of what is stated below was from the point of view of the "typical" setup and NOT the specifics listed at the start of the post. As an example, an RPZ backflow is discussed, but the OP stated that ASVF valves would be used... obviously both are not needed]

Check your planned GPM flow rate and pipe sizes before you tie in after the house pressure regulator. If your house is set up like mine, you've only got a 3/4" copper line where the water line enters the house. That would limit your safe flow rate to aroud 5-6 gpm. Many residential sprinker instilations want higher flow rates than that (to avoid having tons of circits). To allow for flow rates in the rang of 12-14 gpm, you want to tie a 1" line right after the meter (unless they already have a 1" main running to a more appropriate spot to tie into.

Since having enough pressure isn't an issue for you, I would think you would opt for fewwer circuits and want flow rates in double digits.

The other negative to to making the connection AFTER your house regulator is that pressure then could become a problem for you (depending upon how your system will be set up). As an example, if your house regulator is set to the standard 50 psi and you're required to install an RPZ back-flow preventer, that means by the time the water gets to and through the valves, the pressure in your lateral lines leading to the spray heads will only be about 35-40psi (not including friction losses).

So while your particular situation may call for something different, I would think the best set up is likly to be for you to tie into the main just after the meter with 1" pipe, take that to your back-flow device and then a pressure regulator (the Watts 009 RPZ is designed for pressures up to 175psi) and then the pressure regulator. And if you buy a regulator that can be adjusted (more than the $10 models I pointed out before), you'll have the flexability of having as much (or as little) pressure starting at the control valves as you want because you could adjust the pressure of the irrigation system independant from the house (i.e. leave the house as the standard 50psi, and set the irrigation system to 70psi).

And yet another reason I just though of as to why you might not want to tie into your water main after the house pressure regulator... all the water for house use and irrigation use would flow through pipes up through the pressure regulator. So if you do have that 3/4" copper pipe, your 5-6gpm flow capacity would be for the combination of both house AND irrigation. So unless you only plan on running the system as say 3 o'clock in the morning, you'd need to design your irrigation system to stay under 5gpm.


Supreme Member


Thursday, July 27th 2006, 5:15am

Ritchie Rich,

I see that upon reviewing the first couple of posts that you were asking about more than just your 110 static pressure and what to do about that.

So now I can tell you why you've been directed to rather than having your questions answered directly... (question about pressure being the exception)...

... you basically asked "How do I design my irrigation system", and that's basically a pretty tall order. There are LOTS of things to consider, and while you've given a lot of details on what you've got planned, more information is really needed to properly design the entire system. Designing an entire system is beyond the scope of answering basic questions and helping one-another throught the forums. So you were directed to a site that really has all the information you need to learn how design an irrigation system. Yes there's alot to read, but again, if you're going to do an irrigation system your self, you have to take the time to do your research. It would be quite inappropriate in ANY forum for someone to pop in and say "I want to do 'X' but don't know how, can you guys tell me everything I need to know so that I don't have to research the answers may self?". Now I'm not saying that's exactly what you did, but you basically started by asking some wide open questions that that is why you were directed to

Now you can see that based on my posts above, I've tossed out a bunch of information to consider on the subject of what to do about the fact you have 110psi static pressure and suggestions on where to tie into your water main. Since this thread was intitled "Off the Charts!!!" refering to your pressure issue and we've got that pretty much covered, how about starting a new thread for what ever is your next question. Keep in mind, the more specific the question, the more likely you are to get a specific answer. Even the seemingly simple question of "how many circuits do I need?" is really a wide open question that can once again illicit the answer "".


Starting Member

Posts: 1

Location: USA


Monday, July 31st 2006, 4:49pm

This is my first post but I have to say that people who don't understand the design process may perhaps not understand the scope of their questions. I thought using the tutorials was a reasonable response considering the breadth of the question.

What I haven't seen here (did I just miss it?) is the "design capacity" of the system which will determine the maximum flow (gpm) of any one section. Without that info, you really can't zone your system effectively.

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