Water pump question...

nwmn

5 year old buck +
So I purchased a 3" high pressure pump 2 years ago to help irrigate my pumpkins using a large sprinkler.

I have the opportunity this fall to supply a local grocery chain with pumpkins for Halloween and want to utilize this pump and build an irrigation system that can double to water trees I have planted directly next to my pumpkin patch. I currently have 350' of 3" lay flat hose and 300' of 2" lay flat hose that I've used and it does a pretty good job supplying enough water to the sprinkler to shoot about 100'. I wan't to work smarter and not have to deal with that length of hose as it takes forever to move.

My question(s)..
I want to have a main line that will feed lateral lines then neck down to supply sprinkler heads.
I've been trying to source 3" pvc pipe on facebook marketplace but missed out on an opportunity already.

The only thing I've been seeing for irrigation pipe is 6" pipe. Can I feed a larger diameter pipe and then neck it down on the lateral lines?

My thoughts are that it would fill the 6" pipe, and maintain the pressure as it would have smaller outlets off of that.

I've read that smaller diameter pipes lose a lot of pressure and flow rate, so I'd like to keep it as big as possible. Otherwise I will be forced to lug around lay flat hose and suck it up until I find a good deal on 3" pvc pipe.
 
When you double the diameter of the pipe you increase the volume by 4. The area of the 3" pipe is about 7 cubic inches and the 6" pipe is 28 cubic inches. Will your pump be able to handle the increased volume?

Will the total length of your proposed system with pipe be more than the 650 feet of hose? You'll have to make up that extra volume if it is. Maybe you could contact the pump manufacturer and they could advise you on the volume/pressure curve for your pump.
 
When you double the diameter of the pipe you increase the volume by 4. The area of the 3" pipe is about 7 cubic inches and the 6" pipe is 28 cubic inches. Will your pump be able to handle the increased volume?

Will the total length of your proposed system with pipe be more than the 650 feet of hose? You'll have to make up that extra volume if it is. Maybe you could contact the pump manufacturer and they could advise you on the volume/pressure curve for your pump.
I'm not very good with these things lol.

Would the pressure at the sprinkler be the same if i reduce it down to 1.5" on the lateral lines? I was thinking it would operate similarly to a water heater where a line feeds the heater, then the outlet is the same size as the inlet. As long as the 6" pipe is full of water and the pump provides pressure, the outlet lines should maintain that pressure in my mind. I'm probably way off base with my conceptual idea.

Ideally I would run a line from the pump to where the system is and set it up on a T so I can send water either north or south, so in a perfect world I would probably run a line 450' in both directions with a riser on both ends to allow me to connect lay flat hose to it which would extend my reach if I ever needed to. That'd be ideal so I can use that to water my yard as well as trees without needing to haul water around.

Probably best to wait to find 3" pvc pipe and use that?
 
Trust me I'm not perfect with it either. If you know or can determine the GPM output of your pump you can probably find an online calculator to help. Your pump will have what's called pressure head, it's a performance curve for the pump. The pump can't build pressure if it can't fill the lines. I assume you have your own water system at home and not city water. Open all your faucets and flush your toilets and see if your pump hits the cutout pressure and shuts off. If you have too far of a run or too many sprinkler heads the pump may not have enough output to provide pressure at each sprinkler head to spray, you want more than a dribble. Your pump will also have what's called suction head. That's a measure of distance from the water source to the pump. The suction head added to the pressure head gives you the total head for the pump.

It's sort of like and equation. one side of "=" has to be the same as the other side. 2+2=4. If the suction head and pressure head exceed the total head of the pump it won't work. If the total head of the pump is 150 feet you can't have 50 feet of suction head and 200 feet of pressure head. If you do you won't reach the pressure you want.

It's best if you can get the performance specs. for your pump and then work from there. You'll need to know the output of your sprinkler heads too.

I don't mean to make your head spin, but I hate to see you spend a bunch of money and time and watch water dribble out of your sprinkler heads.
 
This is good info to keep in mind. So much math goes into flow and all that, that I never considered. Worst case scenario this year is that I continue doing what I've been doing and not just jumping into something that could potentially fail miserably. It can move lots of water 650' and maintain pressure enough to use my big sprinkler, so I'm hopeful I can find a decent length of pvc pipe to make life a little easier for my unlimited projects I take on :)
 
Theres a crap load of water in a 6 inch line.How far is main truck again and how many and how many feet of lateral lines.I saw 100ft but thats not very far really.I have 200ft of 1 inch black roll pipe that i roll on a metal innerduct spool so with 2 guys it's not bad to do twice a year.Do you feed this water supply with a well? I suppose a 1 1/4 inch line out of well?More volume means less pressure and more pressure equals less volume in pumps usually.So your pump should say for example 150 gpm at 200psi
 
Realistically, if I can outfit a spool for my lay flat hose, I could make life much easier. I want to go about 450' in each direction in a perfect worled with the main, then lateral lines off those every 100 feet or so. I would have valves to control zones so I could supply big guns, or have smaller sprinkler heads to water more zones.

Right now my system is far from perfect, but it works. I need to find someone to help me weld up a transport system with a spool attached and a spot for the pump so I don't have to lug everything around like an idiot. Fire hose is much easier to roll lol.

Water supply is a river or large pond. 350' of 3" lay flat hose, and 400' of 2" lay flat hose.

This is the pump I have. Looks like 10,500 gph at 116 psi. I've also got this sprinkler head and it has plenty of water and pressure at max length.

Northstar Pump
Sprinkler Head

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sprinkler-in-field-11.jpg
 
Find a local fiber optic company and they have 1 inch square tubing reels that would be good.I get 8000ft of 1.25 inch duct on them and if you lived in Ks I would get you some.You mentioned fire hose and that may be easier but then you would have to figure out how to connect things to it.You will also need to keep in mind what your pump will do if you restrict water flow.By the time you get 400ft with a 3inch thats a fair amount of pressure loss.It would be the same as in fire hose or close.Thats why we use 8 inch supply because you don't have pressure loss with 8inch until extremly high amounts.I would still make it so it breaks apart in around 100-200 ft sections
 
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