water pipe uphill pressure issue?

[BrettW]

Hi,
I'm going to lay a water pipe from my house to various beds. The route is upslope but not directly. I'll go here and there to water various spots on the way. Question is, with a submerged new well and fairly good water pressure, will I need to go from 3/4 " pipe and step down to 1/2 along the way to get adaquate pressure? I'm guessing that it is a 5' incline over about a 350' run. Can I just test it with hose pipes and see if I have enough pressure with regular 5/8" hose? I may need to isolate some sections to get enough pressure to the top. Can you run a valve off the black plastic water pipe?

thanks, sorry for so many questions
thanks, brett w

 

[bebster]

5' of rise is not much in the way of pressure drop. One foot of head is equal to 0.433 pounds per square inch of pressure, so that will cause you about a 2 PSI pressure drop.

The issue will be the pressure drop due to friction on the walls of the pipe because it's so long. I would go with 1" or 1 1/4" black irrigation pipe and that will take care of the pressure. Then branch off it with smaller diameter pipe to individual beds.

 

[wjmst]

Also, check the manual for the pump. They usually give a chart of what size pipe you need to maintain the pressure at a certain lenth. If you are going 350' I would use at least a 1" pipe, but the manual will probably state a 1 1/2" pipe is needed.

I have a 1/2 hp jet pump. For 100' ft (length). the book recommends 1 1/4" pipe.

Wes

 

[keeney]

3/4" pipe will be likely be too much friction over those distances for that size pump. Not that it won't work any water, but that you will not get the full rated flow of the pump. Kind of wasting the capacity of gthe pump. At low or zero flow you will still have full pressure. As flow increases, pressure will drop rapidly.

As the other posters have indicated, you want something over 1", maybe 1-1/2".

The recommended line size is chosen such that the friction is fairly negligible for the given distance and you will get the full rated flow and pressure of the pump.

There are a large variety of fittings and valves designed to work with plastic irrigation pipe. If your flow is not sufficient to supply all the zones simultenously, you will need to add valves and only open one zone at a time. The valves can be manual or automatic depending if you want to ivnest in an automatic control system, etc. The size of each zone in terms of the sum of gpm of the heads connected to that zone is chosen to correspond with the available flow at the minimum pressure required to operate the sprinkler heads in question, typically 35 psi or so.

- Rick

 

[notamustang]

Most of the irrigation lines on my property are 1 1/4 to 2" for the main lines. The price of the pipe is more but most of the information I have seen is 1 1/2 will have the least amount of presure drop. My property is about 1300 with a rise of roughly 40'. If you are considering electronic irrigation run the wires with the pipe now and not come back to do it later /forums/images/graemlins/grin.gif Having a timer is pretty nice. You can water while you sleep as oposed to try and water while your wife showers /forums/images/graemlins/grin.gif

Personally I like running the main line as straight as possible and then branch off from there. Usually a valve at the main and then a valve at the location (irrigation or hose spigot) to isolate any troubles and not having to drain the main line to work on something. I have aggresive cyotes that will chew into the pvc to get water from time to time plus my tractor attacks them too. I know where every PVC line at my house is, I have hit them all at least once /forums/images/graemlins/smirk.gif

 

[Highbeam]

Necking down a line to get more pressure is a common misconception. The hose squirts farther from a hose with a smaller orifice, right? No, well yes but the flow rate is smaller.

You could run a 6" line and you will still have the same static pressure at the end of the run as if you used a 3/4" pipe. When you put a tiny hole at the end of each of these pipes, you will get the same squirt of water. The bigger the hole, the shorter the stream from the 1" pipe will be in comparison to the 6" line. This is because the bigger hole allows more flow which speeds the water in the pipe which creates greater losses due to friction. The water velocity is higher on the smaller pipes so you get more loss from a smaller pipe.

Bigger is always better when laying pipe. If cost is a factor you must go smaller but at the cost of head loss.

 

[Catmando]

Highbeam has it correct. The size of the pipe will depend on how much water you want to pump.

Are you going to pump water to all the outlets at once?

You did ask about valves so maybe you plan on isolating each branch and only using water at one outlet at a time.

What is the gpm rating of your pump?

 

[rambler]

Agree with Highbeam, necking down the pipe will hurt you, not help you. Looking at it wrong, you will not increase pressure by going to smaller pipe, you increase available water by using a larger pipe all the way through - less friction.

--->Paul

 

[RalphVa]

For irrigation, I was looking at 1-5 gpm. A 3/4" pipe is plenty. This is what I have about 1200' of across and down my hill to orchard/vineyard and then garden and on over to my pump pad on a little stream. With 100' of elevation drop, I get plenty (43 psi) of pressure at the bottom of the hill from my rain tanks at the house. As backup, I have a little 60ish psi 12v water pump if I run out of rain tank water in a drought. My little stream never ran dry in the drought 4-5 years running 2 years ago.

I've cutoffs at the orchard/vineyard tapoffs to each of the tree lines. These are those little hose type ball valve cutoffs. I've also PVC ball valves down below at the garden to cut off to it and to the pump slab.

I'm a chemical engineer. I used to size piping in refineries. I looked it up in my Cameron Hydraulic Data Book to size the 3/4" pipe. Unless you want to run one of those wastefull overhead irrigation sprinklers that take in excess of 5 gpm, 3/4" is plenty.

For 350', just buy a roll of 500' of black polypropylene pipe and just roll it out. Use the rest for short runs to water other stuff. For trees, just drill a 1/8" hole where the tree is and direct it down into the ground. If you run out of plypropylene, just use pieces of old hose.

Ralph

 

[rlee6]

</font><font color="blue" class="small">( For 350', just buy a roll of 500' of black polypropylene pipe and just roll it out. )</font>
Where can I buy it? Thanks.