# Sizing main water line from irrigation meter



## mwemaxxowner (May 30, 2020)

Hey folks, I found my way here from a Google search. I have a question that I can't seem to totally answer from Google searches.

I once worked for a commercial landscaping company. I dealt mostly with the grading, fencing, planting shrubs and trees, and laying sod side of things. However, I did witness just enough of the irrigation side of his business to get myself into trouble here at home.

We have a new house and I have laid centipede sod, and I have thrown together a quick and dirty "above ground" irrigation system for now using one maxi paw pop up rotor, and a few Rainbird P5r+ impacts.

I'm lucky that I can throw almost to the road from my shrub bed, so these sprinklers are placed in the edge of the bed, fed by 3/4 water hoses and a 4 outlet orbit timer.

My first water bill after installing the sod was... elevated. For every gallon that I put on the yard I had to pay for sewer use too. I've had another meter that was on my property activated for irrigation use that will not be billed for sewer use also. Therein is where my question begins.

My house has about a 100' run of main water line that is 3/4 pex. It only had one spigot, which was at the end of that main line, and had about 3' of half inch pex branching off of the main line to feed it. My static pressure is only 40 psi, and from that spigot I was getting exactly 5 gpm flow. Still, I was able to achieve just over 40' of throw from a cheap plastic Gilmour impact. After testing with one of them, that's why I bought the Rainbird P5r impacts and the maxi paw, as they are similar. Heavier brass impacts seem to not do as well with my low flow and pressure.

This afternoon, I dug up my main water line about 15 feet from the meter on the opposite end of my house from the original spigot. I placed a tee there, and ran 10' of 3/4 pex to a spigot that I mounted on a privacy fence beside the house. I was extremely pleased to test that, and see that I get 7.5 gpm of flow from that spigot just from eliminating about 85 feet of main line. I have not yet gotten to test whether that makes a difference in the throw of my sprinklers.

I'm interested in that because I'm about 8 feet or so shy from making it ALL the way to the road and being able to cover all of my grass. If I'm not able to make that happen, though, I'm fine with it.

The irrigation meter that I've had activated is a looooong run away from the house. I'd say I'm probably going to have to run it 150' to tie it into the spigot that I added this afternoon. Further for the other spigot.

That meter currently has nothing but a ball valve right after the meter. I have no idea what size the meter is, but if I had to guess probably 1 inch? Based on the size of the main line that they ran to my house and the flow I get over there. I don't know if that's a good indicator.

I'm trying to decide what size pipe to run when I pipe the irrigation meter to my house where I can use it. I was planning to use 1" pex. Now, after seeing what different 80' made in the gpm delivery on what I have existing already, I'm wondering if it would be worthwhile to use larger than 1" pipe. I'm hoping to preserve as much flow and pressure as possible since it's so low already.

Being able to throw from my shrub bed to the road allows me to put irritation in without having to run trenches through my yard. My hope is to, eventually, get a DC irrigation controller, and run something similar to what I have set up now, but with a manifold, and "real" valves with either 42sa rotors or possibly sticking with the impacts.

I've said a whole lot of stuff to give you guys some insight on what and why I'm trying to do, but I'm a nutshell I'm curious what size main line I should try to run for 150' or so from my new irrigation meter. 1", or would even larger be of benefit to me? Even if the meter itself is only 1"?

Thank you all for taking the time to read the lengthy post, if you did.


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## mwemaxxowner (May 30, 2020)

I was actually preparing to set up an irrigation controller with one valve, and run 4 sprinkler heads as one zone. Then I discovered that I can only get the throw that I want if I run one sprinkler at a time. That means I'll have to run 4 or 5 separate zones as a single sprinkler head. That complicated the plumbing and digging immensely, which is why I abandoned that for now as I don't have the time, and an orbit timer with 3/4 water hoses hiding under the pine needles is going to do the job for now.


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## mwemaxxowner (May 30, 2020)

I'm elbows deep in the irrigation tutorial right now. Wooooooooooow what a learning tool!

I believe it has answered my questions. I.e. there's no reason at all running the main line with 1.5 instead of 1 inch pipe would be wasteful!


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## bernstem (Jan 16, 2018)

Bigger is generally better within reason. Figure out what your flow is right after the irrigation meter. A 1 inch water meter will flow 25+ gpm and the water company generally won't install them on lines that are not expected to see higher gpm flow (i.e. they probably wouldn't put a 1 inch meter on a 3/4 inch main line with a maximum flow at 11 gpm). If you are getting that much flow, you would want at least a 1.5 inch pipe, and if pressure is an issue, 2.5 inch.

https://www.irrigationtutorials.com/pipe-and-tube-pressure-loss-tables/


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## mwemaxxowner (May 30, 2020)

I will work on rigging up a connection to the ball valve with a short section of hose so I can test the flow and pressure directly off of that meter. I'm assuming it would have similar pressure and flow as the meter that services my house, but it would be a very pleasant surprise to find that it is more capable! The meter that services my house gives me just shy of 40 psi and 7.5 gpm after about 25' of 3/4 pex AND going through a hose bib that's plumbed off that 3/4 pex.

The irrigation meter itself is a new "smart meter" or something that they mentioned is very expensive and it's locked up like Fort Knox. I can't get into the box to take a look at it. The meter that services my house is not like that, it's just a regular old meter and I can get to it.


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## mwemaxxowner (May 30, 2020)

The water meter servicing my house was mostly full of sand and silt. I just worked on uncovering it a bit and confirmed that it is a 3/4 meter. There is also a 3/4 main water line from it to my house.

I checked on the irrigation meter that I had put in, and there is a 1" copper pipe coming out of it and a pvc ball valve with an open threaded end. So it'll be easy peasy to set up a hose thread adapter and run some tests on it.

Since that new meter has 1" pipe exiting the box, does that mean it's a 1" meter? I find it odd that the meter servicing my house would be 3/4, but another meter 150' away would be different. But who knows.

Also, I pulled some measurements, and the irrigation meter is 160-170' away from the first spigot I have on my house, and the most likely location for a valve box if I ever go all in and install a full on below ground system in.


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## bernstem (Jan 16, 2018)

1 inch copper main will flow ~18 GPM. 3/4 inch copper main will flow ~11 GPM. You probably have a 3/4 inch meter on the irrigation line which will flow ~20 GPM. Ultimately all that matters is what you get when you test flow and pressure.


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## mwemaxxowner (May 30, 2020)

Well, I finally got around to getting the pipe and digging the trench!

I'm laying 2" pipe. The old irrigation that I'm tying into runs from a 2" meter, which the homeowner bought himself and had the water company install. He told me I may be able to do the same.

I measured the flow from a spigot on the side of our pool house, which is currently plumbed to his irrigation meter which is the 2" meter, and that spigot flows 10 gpm. Double what the outdoor spigots at my house flow with my 3/4" main and 3/4 meter.

I may price meters and look into that option later on down the road if this doesn't flow well enough.


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