## Calculate Water Flow For A Sprinkler System – Gallons Per Minute

A common question asked is how many heads

can I put on a zone. In order to answer that we need to know what the available water is

at the source at a certain pressure. A bucket test is a good way to determine this. To perform

the bucket test you need to have an apparatus similar to this. We’re going to hook onto

a hose bib with a hose adapter. Then the next thing I have is a pressure gauge. After the

pressure gauge I have a shutoff valve and then a short piece of hose. What I’m going

to do is I’m going to open the hose bib up all the way. When that happens, I will have

zero pounds of pressure. I can’t operate a system on zero pounds of pressure, so I will

slowly shut off the valve. That will build up back pressure to simulate what the head

requires. In my example, I need 30 psi. Once I achieve that, I’m going to put the end of

the hose in a five-gallon bucket and I’m going to time how long it takes to fill up the bucket.

It took us 23 seconds to fill up our five-gallon bucket. Now to do the math we’re going to

take the five gallons divided by the 23 seconds, and that would give us gallons per second.

We want gallons per minute so we’re going to need to multiply that by 60. In our example

you’re going to get 13 gallons per minute. Now if I know I’m using a sprinkler head that

uses two gallons a minute, I can put six of those heads on a zone. You can find the products

that we use to perform this test at your local Ewing branch, or you can visit us online at

ewingirrigation.com.

old video

This is great. Building one of these for next season.

Are these US gallons?

This'll work for a city water system with constant flow and pressure. What if you're on a shallow well system. How do you calculate, when the pump pressure constantly changes depending on faucet openings?

Hose bibs have only a 3/8 diameter hole. To calculate GPM remove HB install a gate valve

Excellent information…. thanks a lot!!

One of the few videos I've seen that show you need to check your flow at the psi you are looking for. There can be a huge difference. You may get 20gpm wide open, but your psi is so low, your heads may only spray 5ft because you thought you could put 20 heads in 1 zone. Why these other "sprinkler" guys don't tell you that you need to see what your pressure is, is idiotic imo.

This is where most if not all irrigation designers fall short. Your irrigation system should be designed according to resident meter size. 5/8" meter 20gpm, 3/4" 30gpm & 1" 50gpm & psi. Many irrigation systems are tee'd off before the home,the home is usually regulated. In addition a 3/4" hose bib has a way smaller diameter than a 3/4" full port ball valve hose bib. Just food for thought.

Building a system on a mine site with 42 sprinklers each using 135 L/min. Still the exact same theory, only I have flow meters to help do the calculation/ measuring

How do u know what pvc size to use for water line and sprinkler head line