# System Design Question



## mmicha (Apr 20, 2018)

I've been reading lots about sprinkler design and such. I thought I'd look at the my own system that was installed years ago.

It seems to me based on the ranges that are provided to you from a city for water pressure and such it is hard to build a decent system.

For example, my static water pressure is at 40 psi. Once it goes through the required RPZ backflow, I'm already down to 28 psi. It still has to travel through the main and into the laterals.

When I test at heads in my back yard I've got like 22-23 psi at each head. The zones only have three heads on each.

How can you actually have 30 or 40 psi at a head in a residential setting when the starting pressure provided is usually around 40-45 psi?


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## g-man (Jun 15, 2017)

40psi static is really low. Call your water utility and ask them what is their target pressure.


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## mmicha (Apr 20, 2018)

g-man said:


> 40psi static is really low. Call your water utility and ask them what is their target pressure.


That's what I'm thinking @g-man . I just reached out the city and will see if I can get it increased. I'm thinking you need between 50 or 55 to even start to think about a system.

50 would give me around 33 psi at heads, and 55 closer to 38.


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## mmicha (Apr 20, 2018)

Sadly after talking to the city with regards to my low water pressure, they came back after testing it at the hydrants near by that it is at 42 psi. I also checked my neighbors and it is similar.

He basically said with a long email and stuff related to the water towers in our city that for my area that isn't unexpected. Originally he had thought they should be between 55-60 psi before further looking at my area.

So it seems that if I want better pressure, my research tells me I'd probably have to install a irrigation pump after my backflow preventer and a start relay... Not sure if anyone is familiar with that...


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## TC2 (Sep 15, 2017)

I'm not an expert, but if I have the mechanics straight, increasing the pressure will increase the GPM output of your sprinklers, but you're not increasing the total amount of water available. Assuming your current heads are maxing out the current system, a higher pressure would reduce the number of heads you can use. You need to check your GPM to see what kind of wriggle room you have.

If you need to increase GPM, then it seems to me you'd need a reservoir before your pump that would need to be large enough to provide the extra water required over the time the sprinklers are active (or breaks are added to allow some time for the reservoir to refill).


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## Slim 1938 (Aug 24, 2019)

My pressure at hose faucet is 40. I cant remember GPM though. My meter has a 1" valve and i tee'd off it to my backflow valve. My main irrigation line is 1 1/4 pvc. I can run 3 rainbird 5000's per zone with no issues at all. I dont loose any pressure in the house either.


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## TSGarp007 (May 22, 2018)

gpm probably isn't an issue since you have only 3 sprinklers and are on utility water. Unless you're filling a bathtub or something at the same time.


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