Piping Water 2000 Feet - Rough Terrain!

I've read posts on these valuable forums for years but this is my first time posting. I have a rather larger water-distribution problem on my hands and could use some advice/opinions on getting water to a future garden site. Hopefully some of you can help!

I have been building a market garden and homestead on 20 acres of high chaparral in Southern California for the past two years. The terrain of our 20 acre property is extremely varied. Granite outcroppings (steep granite hills/almost cliffs) surround the property on two sides. There is a difference of 150 feet in elevation between high and low points. There are three flat areas with relatively deep soil where I'd like to focus my efforts on annuals and perennials. Bringing water to two of these areas is the reason I'm posting here today.

I would like to pipe water approximately 2000 feet from a large water tank beside the well to the location of our permanent market garden. The tank would be at an elevation of 150 feet above the garden so it seems that pressure won't be a problem. The 2000 feet of 1 1/2 inch pvc pipe would be buried at 18 inches and would follow an existing trail that avoids (a) large boulders (b) existing trees and mature shrubs (c) a wash/watershed that I definitely do not want to disturb. The big challenges are the winding nature of the trail (I would need to add approximately ten 45 or 90 degree fittings to the pathway of the pipe) and the slope of the terrain (I would be running a trencher across a 30 degree slope which is challenging and expensive!). I dug my first 350 feet of irrigation supply by hand and I will never dig a large section by hand again.

After two years of walking, observing, thinking, and talking to neighbours I have not found a simpler way to bring a buried water line to the site.

So my questions are:

(1) Without seeing the site.... Any other ideas to approach this crazy project?!?
(2) Does anyone have experience running a large trencher across steep slopes? I have run one for a day across much more moderate slopes and it was a piece of cake.
(3) Any ideas on alternatives to rigid PVC? Nobody seems to think that flexible HDPE pipe is a good idea. I've never worked with HDPE before.
(4) Should I just hide 2000 feet of vinyl tube among the shrubs and boulders and avoid trenching altogether? The unfortunate aspect of this strategy would be that the line couldn't be pressurized permanently. I'd have to feed a second water tank or have a wifi integrated valve all the way back at the well.

Thank you all in advance! Now that I'm a registered member of this community I'll do my best to contribute! Off to try and do a bit of that now...

Hi Jonathan, welcome to the forums!

A bit more info would help us to help you even more.  How much watering do you plan to do with this water supply?  Drip irrigate or 20 sprinklers at the same time?  The volume you need will greatly affect what piping you can get away with.  Also, I'm assuming this is just for irrigation, not potable use?  And lastly, I'm assuming you don't have much of a problem with frost in the ground...

I'll give some feedback and we'll see what everyone else says.  That elevation should work very well for developing pressure.  If my math is correct (doubtful), you'd have around 60 psi of pressure at the garden.  That can do anything you need.  

For my garden I pump water with a 1.5" poly pipe.  I can run 6 oscillating arch/fan style sprinklers at the same time.  I could probably do more if the pump had more guts.  That line is 250 feet long and has 4 90 degree elbows in it.  I laid it on the ground in the woods and then buried it 6" or so where I had to cross the lawn.  So I don't know that you need to go 18" deep unless you really want to.

My answers:
(1)   I'd just run 1" to 2" black poly pipe for your water run.  Hide it in the bushes or bury it a few inches deep.  The 1.5" pipe comes in a roll and likes to stay in that shape.  So straightening it out and routing it around obstacles takes a little work but it's very doable.  Especially if you lay it in the hot sun for a half a day first.  Then you may not need elbows since it can weave around trees/rocks/etc.  Maybe even lay it out on the route you want it to take and let it bake into shape in the sun for a week, then bury it a bit.  Then you won't be fighting the coil memory as you try to bury it.
(2)   No experience but I wouldn't think it would be much fun.  Especially if you hit rocks.
(3)   I'd avoid rigid PVC due to cost and all the fittings you'd have to mess around with.  Poly for me...
(4)   I'm not sure what vinyl tube is for irrigation.  I think the poly is just fine if left pressurized and in the sun.  If you get freezing weather you'd want to drain it in the fall.  But when I lived in Utah I used poly for underground sprinklers and buried it 6" and never drained it and it never cracked.

Good luck!

Mike Jay wrote:Hi Jonathan, welcome to the forums!

A bit more info would help us to help you even more.  How much watering do you plan to do with this water supply?  Drip irrigate or 20 sprinklers at the same time?  The volume you need will greatly affect what piping you can get away with.  Also, I'm assuming this is just for irrigation, not potable use?  And lastly, I'm assuming you don't have much of a problem with frost in the ground...

Thanks for my first reply Mike!

First, a few answers to your questions.

Irrigation Plan - I plan on irrigating an acre split into six to eight zones - more zones if really needed. I will be using low-flow toro drip tape to irrigate 30 inch garden beds. The low flow tape allows for me to water lots of space with relatively little flow. I haven't calculated my gallons per minute but my experience with the product suggests that I should be totally fine! I'd still like to able to run a few sprinklers at a time but really just once in a while - the scorching days of summer, to establish germination in a cover crop... etc.

Potable Use - I'll drink from the hose but will discourage any guests from doing so - so no...

Frost - Nothing freezes if below an inch here. On the surface a hose will definitely freeze solid on a very cold night. I usually just wait until the middle of the day to run irrigation after we've had a particularly cold night (which is 20 degrees F here!).


And your recommendations...

Thanks for sharing your thoughts and experience. I figured that poly (which is what I meant when I wrote "vinyl") should work but wasn't too sure. Good to hear that you have a longer run that is pressurized. I definitely enjoy the low price point for the larger diameter pipe. My only concern is if I had a break from a freeze or from a coyote tearing it apart (this has happened!) then I would lose several thousand gallons of water. I still think it's the most viable option for now. I think roughing the hose into the top few inches of soil like you suggest would prevent most problems.

The 18 inch trenching depth is really just a goal in case soil erodes or I build a structure in the future. Probably a major overbuild!!! With the hydraulic trenchers I've used in the past I could dig down to 24 inches at a rate of several feet per minute. Backfilling and tamping was quite a job though!

Thanks again! Glad to have some advice from off the property!!!

Good, then it sounds like we have a possible option for you.  Once you know your gallons per minute you can figure out if you even need to go bigger than an inch in diameter.  Just to clarify on my set-up, the pipe is only pressurized when the pump is running (10x per year).  So it does not experience pressure all the time.  But I can't imagine that it couldn't handle it.  It's very tough.  I'm kind of surprised a coyote could bite through it...  Can you get to the tank to open a valve on days you want to water?  That would relieve some anxiety about losing all your water in the case of a failure.

Mike Jay wrote:Good, then it sounds like we have a possible option for you.  Once you know your gallons per minute you can figure out if you even need to go bigger than an inch in diameter.  Just to clarify on my set-up, the pipe is only pressurized when the pump is running (10x per year).  So it does not experience pressure all the time.  But I can't imagine that it couldn't handle it.  It's very tough.  I'm kind of surprised a coyote could bite through it...  Can you get to the tank to open a valve on days you want to water?  That would relieve some anxiety about losing all your water in the case of a failure.

The coyotes have only chewed through half-inch stuff. I imagine the larger diameter pipe is much thicker. They are thirsty creatures out here - cleared out a few hundred pounds of my watermelons this year too!

I was thinking the same thing when it comes to timed valves - I could pressurize during scheduled irrigation and then have an automatic shutoff when it's not in use. I irrigate every day so it will have to be an automated setup. Since you first posted I have been reading up on the pipe and it does look like it would take the pressure (rated to 160 PSI) though I'd have to look into the potential surge pressure after an irrigation valve closes.

Yeah, the 1.5" stuff is very thick.  I don't think you could manually get a sharp stick to penetrate it if you tried (unless you cheated and used a mallet).

If pressure is a problem, they make pressure reducing valves that don't require power and are used to meter down pressure for houses.

Do you have power at your water tank?  Finding a large diameter timer valve that doesn't require power or water pressure will be a challenge.  Most watering timers that you put on garden hoses rely on the city water pressure to help them actuate on and off.  There are solar powered timer valves that don't need water pressure but they are more like 3/4" in diameter.  

Mike Jay wrote:
Do you have power at your water tank?  Finding a large diameter timer valve that doesn't require power or water pressure will be a challenge.  Most watering timers that you put on garden hoses rely on the city water pressure to help them actuate on and off.  There are solar powered timer valves that don't need water pressure but they are more like 3/4" in diameter.  

I've got power for days up at the tank - it's the only place my county would let me bring electricity since we have not yet built our house. The pressure tank for our property currently feeds our "starter" market garden but it has its limitations. This is why I'm comfortable with irrigating large areas with low-flow drip irrigation. A large holding tank will solve these issues and allow me to move the garden farther away... hopefully!

And yes, those 3/4" valves don't seem to let much through. I tried to use one for this year's garden and it wouldn't let enough water through. Thankfully I do have 100 amps to make things happen!

Lots of thoughts, maybe not so organized

1. Second Mike Jay's suggestion of poly pipe (technically it's called poly tubing) . It is so much easier and cheaper than PVC. I use thousands of feet and rarely have a problem.
2. Sounds like a nightmare
3. See above
4. I leave my main line pressurized a lot. In several years it has never let go or blown out, even at the bottom of the hill where it is 90-100PSI. I use Direc-Loc fittings, and this is 1" line. They are totally bomber. Now there is a caveat here: some cheaper poly pipe of the smaller diameter is much thinner walled and I did for a while have some blow outs when the line was pressurized in high heat. So that may be a problem where you are. If you bury it though, I don't think you'll have an issue. Also, I get hard freezes here and one of the great virtues of poly tubing is that it is flexible enough to handle a freeze. Not that I tempt fate.

Timing: I use 1 1/2" solenoid valves that are 24v. They are about $50-60 but allow you to power timed valves in the field using just a car battery and a small solar panel (24w, 80Ah battery in my case). A real benefit is that you can put solenoid valves on your zones. For those I use 1" valves and they are very reasonable especially if you buy them in bulk. The 3/4" valves you see in the big box stores are worthless. Check out Irrigation Direct online. The valves I use the most of are something like this: https://www.irrigationdirect.com/product/electric-solenoid-valve-1-fpt-female-pipe-thread-24vac-dfv100- Note the quantity discounts.

I also did what you are thinking and put a timed valve on the main shutoff so that in the event of a blow out I wasn't losing water all day. It's not a great solution, one, and two even the big valves really restrict flow. My new solution is an Arduino that uses a pressure sensor and will kill power, send an alarm, or whatever is appropriate if there is an out-of-range pressure detected. I haven't implemented it yet, but the idea is quite sound. See https://www.sparkfun.com/products/12909. You can buy such things commercially for $100-150, I think.

As for flow rate, it's super easy to calculate for drip tape since they are very consistent at a given pressure. I saved myself quite a bit of money by figuring out that the way I water only requires me to have a 1" main line -- and of course if you are using timers for each zone you can space it out. What was important was to optimize the set up so that the main never restricted flow and all the valves were on the sub-lines, etc. On the one main there are 42-45 x 150-175ft rows. Each sub line has a gating PVC ball valve so the main can be at full pressure to make it up the hill to the last row. For me this arrangement has been absolutely superb. I suppose if could have found 1 1/4 or 1 1/2" poly locally I would have used it but it is REALLY nice to have standardized fittings.

Oh, and pressure tanks. Don't bother. If you are irrigating that much it won't make any difference. Mine did go through a PT until recently, but after about 30 seconds the well pump just runs, which means all you are doing is restricting flow. On the big storage tank, it's worth doing your calculations for GPM and total gallons so you can size it appropriately. In my situation even a 5000 gallon tank isn't enough, but I have a 100 GPM well so I don't need it.

Initially I mis-read the 150' drop from the tank as a 150' gain so I started talking about head loss. I have about a 75' drop and pick up a lot of pressure that way -- it's the same number as loss, so 150' x .433 means you will gain 65 psi, but minus the friction of the pipe... maybe a 55 PSI gain or so net. It's not a big deal if you either use a pressure regulator or gate it with a ball valve.