Need help with size of waterline!

[andrewj]

Hi folks...

I have a 1 and 1/4 inch waterline that travels 500 feet from the county tap to my home.

I need to run water another 1400 feet up to a vineyard for drip irrigation. I am not concerned too much about volume of water since it won't be the typical water sprinkler type of irrigation, but low flow drip. I know there is a hard science on size of pipe, length of travel, elevation, etc. but I'm not sure where to begin.

I am not a scientific person so my knee jerk reaction is to hook it up and see if it works! Obviously, that is risky and expensive in hard times..

Thanks in advance for any advice.

 

[schmism]

the issue is pressure.

for every foot you go up you loose .433 psi

10'=4.33 lbs pressure

youll need to know what your min pressure needed for your low flow system is, they can need decent pressure to push through the filters that are used to ensures the nozzle don't clog.

a 45lb supply at the house quickly drop's to below 30psi if you have 30' hill to climb.

no amount of pipe diameter or flow rate will fix your pressure issue associated with headloss (if you have one)

 

[Bentwrench]

Here's a sight that has loads of info for all your water supply needs.

Water Tanks, Septic Systems, Plastic Water Storage Tank Systems, Pressure Tanks, Underground Cisterns

 

[RonMar]

What Steve said. 1400' of length is one thing, but how much vertical rise is involved?

 

[andrewj]

What Steve said. 1400' of length is one thing, but how much vertical rise is involved?

thanks guys. it goes down across a draw 20 feet down then back up again, so that the eventual spot for the water tap is same elevation as the starting point. Does the down hill cancel the uphill?

 

[Shmudda]

thanks guys. it goes down across a draw 20 feet down then back up again, so that the eventual spot for the water tap is same elevation as the starting point. Does the down hill cancel the uphill?

Yes, the down hill does cancel the up hill for the final elevation difference as any liquid will seek its own level no matter what it is in. What it doesn't cancel out is the head resistance the hose creates. In addition to the fluid having to overcome any elevation difference it also has to overcome the resistance to flow the pipe or hose creates too from the roughness of the inside diameter. Usually, you can find the flow resistance (head loss for specific length of hose) for the hose you are using thru various piping manuals or directly from the supplier you are purchasing it from. Hose will offer much more resistance to flow then what pipe will, but you can overcome that by going to a larger diameter hose for the application which will cut down on the frictional loss's on the ID and provide a larger volume of liquid to the final destination.

Hope this helps.......

Craig

 

[cddva]

As stated, you need to know what the min pressure required by your irrigation system is and ideally what flow rate you should operate at (ask your drip irrigation supplier). Then calculate pressure loss for 1400' of 1-1/4" pipe or whatever size you plan to run. Add some margin for pipe fittings (assume equivalent length of pipe). Here's a link to a chart as an example of pressure loss due to friction per hundred foot of pipe at a given flow rate, PVC Pipe Schedule 40 - Friction loss and Velocity Diagram. Note: the larger the pipe diameter the less flow resistance for a given flowrate. Since your elevation change is a net of 0 feet you can ignore it. If you don't have sufficient pressure you may need to add a booster pump (see link provided by Bentwrench). Good luck.

 

[EddieWalker]

How much preasure do you have at the location you will start this line? You don't need allot of preasure for what you are doing and for volume, you can leave the line open as long as it takes to get the job done.

Buy an inexpensive preasure gauge at Lowes or Home Depot in their sprinkly area. It screws onto a water spicket and will give you a starting number. If you have a normal amount of preasure, like 60 pounds, then it's just simple math to figure out what you should have for preasure at the end of the line depending on the size of the pipe and the elevation change.

My guess is you should just up the pipe size to 1 1/2 and live with what you end up with at the end.

Eddie

 

[andrewj]

eddie, I love the way you put that, and I agree. run the line, larger than the other one and live with what comes out the end! haha.

 

[ampsucker]

you're right, this is not a project to build first and see what happens later. 1400 feet of pipe and the trench to bury it is a significant investment. i would do a little math and some leg work before starting.

for example, how large is the vineyard? soaker hoses are deceiving in that they can lay down a lot more water than you would think. going from a solid pvc pipe into a large drip irrigation system is modeled by what is known as a sudden expansion. you go from a specific cross sectional area basically to infinity or a very large cross sectional area when you consider the volume of the manifold, the many different lengths of drip hose, emitters, etc. what this means in practical terms is the pressure drops very close to zero as the volume of water increases to the limit of the supply pipe.

what this might mean for you at the house is that nobody can take a shower, flush a toilet or water the dog while the vineyard is being watered.

on the other hand, say you crank down the outflow valve to the vineyard, increasing the pressure to the house. now, you may not have enough flow and pressure to overcome the soaker hose resistance and push water all the way to the end of the furthest soaker run.

see what i mean? as previously mentioned, get the specs for the system you want to install and make sure you can supply the volumes needed by all the sources (in the house AND in the garden/lawn/vineyard) with the service you have already to the house. then size your run to the vineyard appropriately. you might even save half or more on your pvc costs by going to a smaller line if you can. or, you might find you need a booster pump or that you need a larger line all the way back to the source. it really depends a lot on the volumes of water you need to move and where they are going.

amp