Pressure / Flow loss over long run of pipe?

[lawnmaniac883]

Hi you guys, I am working on a irrigation system for my church. If we could afford to hire an irrigation company to do the install then it would have been done but we just dont have the kind of funds to do that. So, the source is a DEEP well, I believe it is a few hundred feet down and has an inline pump. Not sure how much water it flows, going to see if I can get any literature on it tomorrow but it probably flows an amount comparable to two residential pumps, maybe more and still has lots of pressure.

Now for the question. We are using 1'' mainline over a run of about 450 feet. The mainline doesnt split off into a smaller 3/4 line or the like. Instead we have 1'' T's with 3/4 threads on them for rotors. What I need to know is how much pressure can I expect to lose over such a long run? Is the mainline going to be big enough at 1''? Thanks.

[Dirty Water]

The amount of pressure you lose is directly dependant on how many GPM you will be using with the rotors.

That said, you should design the system around the MAX GPM output of your pump. If your pump is putting out say, 15 GPM, then use nozzles in your rotors that will consume 15 GPM.

Using that 15 GPM number, in 450 feet you will be losing 13 or so PSI in 1" Class pipe, change that to SCH 40 pipe and your losing 22 PSI!

However, even more so important than PSI loss is the speed water is moving in the pipe. The more GPM you shove down a pipe the higher the velocity (in feet per second) is. The general industry rule of thumb is to keep the speed under 5 fps, too fast and you will get lots of water hammer, and possible blown off fittings.

450' in 1" Class 200 at 15 gpm will be moving at 4.3 FPS...close to the limit, but not over it, if you use SCH 40 you'll be at 5.5 FPS...too fast!

If this pump is as big as your say it is, you will probably be putting out even more water. I'm going to say that a 1 1/4" mainline is probably not a bad idea:

1 1/4" class 200 pipe with 15 GPM will lose 3.9 psi over 450 feet and only be moving at 2.7 fps...Much better!

So, I guess what all this means, is that you need to find out your pumps GPM output first. Then ask this question :)

Good luck.

[lawnmaniac883]

Thanks for the reply, I am definately going to try and get some literature on this pump tomorrow before I bury all of this piping. The morons that were going to dig the trench made it too shallow; we told them to make a 8-10'' deep trench and they only made it 3 - 4 inches...tomorrow I hafta rent a trencher and make a real trench then I can see what kind of flow this pump has. I was concerned that the demand I will be placing over this run may cause water hammer...will post back what I find tomorrow.

Another question I have is that if I were to change out the mainline and go from say 1'' to 1 1/2 '' and then reduce that back to 1'' at the end of my run just before I start hitting sprinklers, would this be an O.K. thing to do or do I need to have that 1 1/2'' line the entire run of the system? Thanks.

[Wet_Boots]

Is there some reason you can't just simply run the pump and take some measurements of flow (bucket test) and pressure? Beats the hell out of literature. Then you'll really know what pipe to use.

[greenhorn123]

ok I'll ask, are you planning on putting the heads on the mainlne?

[lawnmaniac883]

Is there some reason you can't just simply run the pump and take some measurements of flow (bucket test) and pressure? Beats the hell out of literature. Then you'll really know what pipe to use.


It is all underground, no spicket to go from. The iron pipe comes out of the ground with a galv fitting on top with pressure relief then goes down to the manifold.

[lawnmaniac883]

ok I'll ask, are you planning on putting the heads on the mainlne?


I am laying two lines in one trench. One makes up a zone and it is 1'' with rotors and some pop ups on it the other is the mainline which will be going to a valve manifold further up the property. From the manifold will be two seperate zones. So the mainline will not have sprinklers on it.

[Dirty Water]

I am laying two lines in one trench. One makes up a zone and it is 1'' with rotors and some pop ups on it the other is the mainline which will be going to a valve manifold further up the property. From the manifold will be two seperate zones. So the mainline will not have sprinklers on it.

Define Rotors and Pop Ups.

I hope you aren't planning on mixing rotors and sprays?

[Wet_Boots]

It is all underground, no spicket to go from. The iron pipe comes out of the ground with a galv fitting on top with pressure relief then goes down to the manifold.So run a flow-and-pressure test from the manifold. It's all well and good to do slipshod prep work at your own home, but one would think you'd want better for your church.

[earlofcrankcase]

Honestly. You should not ask for info if you cant take the effort to know what you have to build with first. (to me) It seems kind of gay to ask for someone else to answer your question when you won't spend 10 minutes of your time first.

( benefit of dought)
city water = time to fill a 5 gal bucket= gpm
Well water, let it flow till the pump kicks back on. Do that bucket deal. Then let it keep flowing and test again after the well has run for a while.
Wells are a good thing but. Like wemen, some are better than others. What your looking for there is a pull down gpm. As the pump draws the water to it. If the table is not large enough the flow will slow down. Main goal with that is to try to have the flow at max sustained output. That way the well pump is not turning on & off. That might take some effort though. So who knows. Keep in mind your building more than their system. (your rep bro)

[jabbo]

Listen to these guys very well,because they are telling you exactly what you need to do, especially that Wet Boots character! I just got thru doing my own system with a well and after I saw what a good job it does(I had to move 1 head) I am glad I listen to them. I went ahead and did the flow and pressure check right from where I was going to tie in with my system. After you get a good flow and pressure reading then all you have to do is alot of planning. Good luck and keeping posting and they will help you right along!!!!!!!!!!!

[rough cut]

Take some time and read the info on this web site. http://www.irrigationtutorials.com/index.html
I put my own system in and have 18 zones running through 1.5" pipe and my longest run is 300ft to the first head. At the casing (where the pump pipe comes out of the well) I have 60GPM @ 55psi. I read almost all of the info at the above site and it helped alot. It will save you time, money and alot of mistakes. Do it once, do it right and never do it again.

[brookviewlawncare]

Listen to these guys very well,because they are telling you exactly what you need to do, especially that Wet Boots character! WOW :cool2: :cool2: :cool2:

[lawnmaniac883]

Take some time and read the info on this web site. http://www.irrigationtutorials.com/index.html
I put my own system in and have 18 zones running through 1.5" pipe and my longest run is 300ft to the first head. At the casing (where the pump pipe comes out of the well) I have 60GPM @ 55psi. I read almost all of the info at the above site and it helped alot. It will save you time, money and alot of mistakes. Do it once, do it right and never do it again.


That is a great site, I am learning ALOT right now. Thanks

[PurpHaze]

Do it once, do it right and never do it again.

Until you get bored and decide to try out the latest sprinkler on the market. :laugh:

[lawnmaniac883]

Ok, I have determined alot thanks to that site, cleared so many things up for me.

1) The mainline that runs 350 feet needs to be atleast 1 1/4'' but I will probably use 1 1/2''

2) Dont mix rotors with sprays, I will watch the sprays blow apart if I try it.

3) Always use the advice from lawnsite members to your advantage. Thanks fellas; any more advice is appreciated. The way I had this thing planned just would not work.

Ok a few more questions here. The line going from the well to the manifold is 2 1/2'' then it eventually goes down to 1 1/4 before it hits 1'' pipe at the manifold. Now, if I use a 1 1/2'' mainline will I be able to take off of the 1 1/4 pipe, the 2 1/2'' pipe or will the 1'' at the manifold flow fine for my 1 1/2'' mainline run?

I plan to operate all of this at 45 - 50 PSI at the manifold which means I will only lose about 5 PSI at the end of my 350 feet of run, right?

I will do the test found on the website and see what the GPM of this pump is at 50 PSI tomorrow, the value that I find should be how much higher than the GPM of my combined heads out in the field?

If I am not making myself clear then let me know, this sounds confusing to me but yall may understand it just fine. Thanks...

[Dirty Water]

Ok, I have determined alot thanks to that site, cleared so many things up for me.

1) The mainline that runs 350 feet needs to be atleast 1 1/4'' but I will probably use 1 1/2''

It could be 1/2" if your only using 1 gpm. You need to find out GPM numbers before sizing pipe. In a real world, I'm going to say 1 1/4" will be fine.


2) Dont mix rotors with sprays, I will watch the sprays blow apart if I try it.

The spray won't blow apart, I don't know where you heard that.

Sprayheads put down water at precipation rates around 3 times faster than rotors. This means that if you mix them, you'll have a swamp from the sprayheads by the time the rotors are done watering.


3) Always use the advice from lawnsite members to your advantage. Thanks fellas; any more advice is appreciated. The way I had this thing planned just would not work.

I've worked on so many DIY systems. It must be discouraging to spend hours and hours installing something, just to have it not work at the end. A month or so ago some guy posted on here trying to fix his horribly installed 1000' median strip watering system, and would plain and simple ignore our advice. And you wonder why it had no pressure.


Ok a few more questions here. The line going from the well to the manifold is 2 1/2'' then it eventually goes down to 1 1/4 before it hits 1'' pipe at the manifold. Now, if I use a 1 1/2'' mainline will I be able to take off of the 1 1/4 pipe, the 2 1/2'' pipe or will the 1'' at the manifold flow fine for my 1 1/2'' mainline run?

Depends entirely on GPM.


I plan to operate all of this at 45 - 50 PSI at the manifold which means I will only lose about 5 PSI at the end of my 350 feet of run, right?

Depends entirely on GPM.


I will do the test found on the website and see what the GPM of this pump is at 50 PSI tomorrow, the value that I find should be how much higher than the GPM of my combined heads out in the field?

You actually want to attempt to match it as close as you can. This will keep the pump from cycling.

Good Luck.

[Wet_Boots]

The line going from the well to the manifold is 2 1/2'' then it eventually goes down to 1 1/4 before it hits 1'' pipe at the manifold. Now, if I use a 1 1/2'' mainline will I be able to take off of the 1 1/4 pipe, the 2 1/2'' pipe or will the 1'' at the manifold flow fine for my 1 1/2'' mainline run?You might want to assume the 2½ inch line was selected for a reason. If you do have a well output of 50 gpm, you have to way upsize everything. Sometimes, on a well, that bucket test turns into a 30-gallon trashcan test.

Many states require a deep well to have its performance logged and reported to the state. The original well driller and/or pump installer would have this information. If you knew the pump horsepower and the water depth of the well when the pump is running (the 'drawdown depth') you could find some performance curves and get an idea of the well's output.

[Dirty Water]

You might want to assume the 2½ inch line was selected for a reason. If you do have a well output of 50 gpm, you have to way upsize everything. Sometimes, on a well, that bucket test turns into a 30-gallon trashcan test.

Sometimes if you have obscenely large amounts of water it makes more sense just to design for what you need and use a PSR. However, that sometimes is rare. Personally I'm all for HUGE zones.

I've got almost 3 acres and the majority of is just a large field. I'll have a 100 gpm source to use about this time next year (12" irrigation line being laid down my street :D) so I'll be able to water the whole field with I-25's or larger :laugh: It's going to look beautifull.

[Wet_Boots]

Why not go for some giant agricultural impact heads? Pipe art, you know.

[Dirty Water]

Why not go for some giant agricultural impact heads? Pipe art, you know.

Like this?

http://www.absolutestockphoto.com/albums/userpics/10027/normal_Absolute_27_5788.jpg

Ok, enough hijacking :)

[lawnmaniac883]

I tried to get some information on the pump but it was to no avail. Couldnt find any specs or owners manual, nothing. They cannot even tell me who installed the pump although I remember the guy I cant put a name to the company. Maybe the small pipe is a problem on the current manifold. Right now they have two zones each has a load of what I would guesstimate to be close to 25 GPM. With that, the pressure relief valve on top of the pump is constantly venting water out of it. This system has no pressure switch on it; the pump is submerged and turns on when the controller tells it to. In place of a pressure switch there is a relief valve.

So far I figure that I will be using 30 GPM per zone with what I have laid out so far; adding 3 zones to the system. The bucket or trash can test should help me determine how much water is really there without going through all of the guess and check BS... There is no pressure gauge on the manifold right now, I will be adding one tomorrow. Whew, you guys are underpaid lol.

Off topic here but have you guys ever heard water hammer so bad that it sounded like a friggin helicopter? Was at a buddy's house last week and could have sworn I heard a helicopter but it was comming from the same area for about 10 minutes right. I noticed his neighbor had his sprinkler system running so I walk over there and it sounded like a jack hammer going at some concrete. Unbelievable...ever run into this?

[Dirty Water]

If the pressure relief valve is opening then the current zones are not using all of the current pumps output. The PRV is to keep the pump from deadheading, which would wreck the pump.

Don't gestimate, you can find performance data for almost any sprinkler head online, go to one of the existing zones, check the nozzle sizes in all of the heads and pull the flow rates off the manufactures website to get an accurate idea of what is too small :) Remember, all you need to do is enlarge the nozzles in those heads until they are using what the pump will actually produce to keep the pressure relief valve from opening.

[Wet_Boots]

Horsepower and depth can get you started on a performance-curve search, even if from some other manufacturer, but actual performance testing is best.

[PurpHaze]

Got PLENTY here. Want some??? :waving:

[Dirty Water]

Off topic here but have you guys ever heard water hammer so bad that it sounded like a friggin helicopter? Was at a buddy's house last week and could have sworn I heard a helicopter but it was comming from the same area for about 10 minutes right. I noticed his neighbor had his sprinkler system running so I walk over there and it sounded like a jack hammer going at some concrete. Unbelievable...ever run into this?

Yeah, I've seen stuck valves do this.

[PurpHaze]

On rare occasions I've seen a valve not fully open that stutters. Gutting of the valve and replacement of the top end takes care of it.

On other occasions I've seen newly installed valves stutter the first few times they close down. After they've been fired a couple of times they settle down.

[lawnmaniac883]

Did a flow test earlier today and at 0 psi (ball valve fully open) There is 50 GPM at the manifold. At 40 PSI there is 35 GPM. My first new zone has 50 psi on the pressure gauge. About to get the second wired up now.

[lawnmaniac883]

Well, an update for you fellas. I got the entire run in the ground, have all three additional zones added on and let me tell you, we have water! Ended up putting 1 1/2'' mainline down with 1'' line to the zones. I have just under 50 PSI on every zone and according to the manufacturer that puts me around 30 GPM per zone. A big thanks to all who contributed to this. Just have some trenches to fill now...BTW what is the best way to bore pipe under a 20' wide driveway/parking lot deal? I know I will need a pro to get this done, just need to know what kind of pro to call? Thanks.

[Dirty Water]

Well, an update for you fellas. I got the entire run in the ground, have all three additional zones added on and let me tell you, we have water! Ended up putting 1 1/2'' mainline down with 1'' line to the zones. I have just under 50 PSI on every zone and according to the manufacturer that puts me around 30 GPM per zone. A big thanks to all who contributed to this. Just have some trenches to fill now...BTW what is the best way to bore pipe under a 20' wide driveway/parking lot deal? I know I will need a pro to get this done, just need to know what kind of pro to call? Thanks.

Call a utility ecavatation contractor or a irrigation co with a directional bore.

Its $8 a ft in my area.