underground water line to hydrant and barn

charlie67May 17, 2012

I want to install an underground water line to a hydrant in the yard and then continue on to a barn. What is the most current type of line in use today/ And if it is some sort of plastic what is the best under ground connection type to use? do barbed fitting and hose clamps hold up, or is there a better way to make and underground connection?

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You may use

Brass Pipe (cost prohibitive),

Copper Pipe types K,L & M in both hard drawn rigid lengths & annealed roll pipe (again,nearly cost prohibitive),

CPVC Pipe (careful here, that is CPVC pipe, Not CPVC CTS tubing which is commonly found in the local big box stores),

Ductile Iron Pipe, (Cost prohibitive, labor intensive and relatively short service life),

PB-Polybutelene Pipe, although with the number of class action suites against PB its doubtful if you could find it.

PE-Polyethelene Pipe- commonly called "Roll Poly",

PEX tubing, Tubing price is reasonable but it requires expensive fittings and special tools.

PVC pipe- inexpenive and easy to install, but it requires straight level runs and a fitting at each change in direction. Being rigid lengths it also requires a joint at every ten or 20ft interval and most underground pipe failures occur at joints.

My recommendation would be PE (roll poly) which is very cheap, easy to install and uses rather inexpensive barb fittings and only a screw driver or nutdriver to tighten the clamps. For direct burial I would recommend nylon barb fittings with stainless steel hose clamps.

Roll poly is commonly available in 60' & 100' rolls but it can be special ordered in 250' rolls so you could make continuous runs with no buried joints other than at the hydrant and the barn.

Regardless of what pipe you choose you need to consult a "Friction Head Loss Table" to determine the amount of pressure loss that would be attributed to pipe wall friction for the length of your run.

If you can tell me the distance from your house of the source to the hydrant and to the barn I will be glad to look up the friction head loss for you.

Also, if you live in a region that is subject to frost the line must be a minimum of 6" below the listed average frost depth for your area.

If the line has to pass through a masonry wall you have to sleeve the pipe through the wall below the frost line.

You also need a "main shutoff valve" and a "backflow preventer" and possibly an air gap (depending on local code) on the source end of the line.

In regards to longevity. I helped my Dad install a PE line from the house to the barn on my Granddads farm in 1959. That line is still in use today, supplying all the water needs for 100 head of cattle, 15 draft horses and all the sanitizing needs for the milk house and milk production equipment and we have never had to perform any repairs on that line.

    Bookmark   May 17, 2012 at 6:55AM
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Agree with Pup, 100%. It's a no-brainer to use PE.

Be sure to take Pup up on his offer to calculate head loss.

    Bookmark   May 17, 2012 at 8:26AM
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Is this pe drinking water rated or approved?

    Bookmark   May 17, 2012 at 4:43PM
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It causes horrible, hideous mutations in lab animals, but other than that it's fine. Do a search for "Creature From The Black Lagoon" to see what happened to the lab guy who first drank water from a PE pipe.

No, really, it's approved for potable water. Look for the NSF approval.

    Bookmark   May 17, 2012 at 5:06PM
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All the pipes I listed above was taken right from the code as pipes approved for potable water supply lines.

    Bookmark   May 17, 2012 at 6:10PM
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Pup,the distance to the hydrant is 100' and then add another 75' to reach the barn for a total of 175'. Thanks for the info from all of you.

    Bookmark   May 18, 2012 at 6:03AM
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In order to properly compute the FHL (Friction Head Loss) we need to know both the length of the run and the expected gpm of flow.

You stated that you are installing a lawn hydrant and continuing the line on to the barn, where I am assuming you will install a second hydrant to protect the valve from freezing in winter.

Hydrants are a variation of a hose bibb and according to the load table in the code hose bibbs are rated at 5gpm.

I am computing the FHL as a two part problem because the line begins at the house (or other source) and runs 100' to the hydrant, then continues on to the barn, so the first 100' of the line has to carry the total combined load of 10gpm to the hydrant, then it is only carrying 5gpm from the hydrant to the barn.

To give you an illustration of how great the effects of FHL are; let us first consider what would happen if you ran a 1/2" line.

For a 1/2" line @ 10gpm the FHL in the first 100' to the hydrant would be 82psi, and @ 5gpm the FHL from the hydrant to the barn would be another 17.58psi for a total loss of 109.58psi. As you can see, even if you had the maximum 80psi at the source end, you would be lucky to get anything better than gravity flow at the barn.

Code minimum for a "water supply line" to a structure is 3/4" so let us see what this will give us.

A 3/4" line @ 10gpm has a FHL of 20psi/100' so the pressure at the hydrant would be 20psi less than the source pressure. A 3/4" line @ 5gpm from the hydrant to the barn would be another 4.29psi loss, so the pressure at the barn would then be 24.29psi less than the source pressure and unless you have exceptionally high pressure at the source this would also prove to be very unacceptable.

If you run 1" line with both the lawn hydrant and the hydrant at the barn open at the same time the loss would be 6.02psi at the hydrant and 8.31psi at the barn hydrant, however we still don't know what the actual dynamic pressure (pressure under flow) is at the source. If the source pressure is below 40psi under flow an 8.31psi drop is significant, especially if you anticipate adding a 50' hose at the barn.

Now let us pour a cup of coffee and think about this whole project for a moment. First off, you only want to have to do this once in your life and second, when compared to the cost of excavation and installation labor the actual price of PE pipe is relatively cheap.

If you were to run an 1-1/2" line from the source to the hydrant the FHL for the first 100' of the run would only be 0.72psi and if you then continued from the hydrant to the barn with an 1-1/4" line the FHL would be 0.33psi for a total combined loss of 1.05psi with both the lawn hydrant and the barn hydrant open simultaneously. This means that even with the lawn hydrant in use, a hose at the barn would still have about the same working pressure as a hose connected to a hose bibb at your house.

Now let us consider the cost of the excavation. If you are overly ambitious you can take it from an old man who has been there and done that, you could dig the trench by hand and save some money, But take it from experience. That would involve about 3 days of arduous back breaking, mind numbing work, and you still have to lay the pipe and backfill. I can assure you, by the time you finish that project, the price of renting a machine looks cheap.

The question then becomes, what machine do you need? Certainly a backhoe can do it, but unless you already have one on the farm a backhoe is way too much overkill for this project.

The preferred machine would be a ditch witch type trencher. If you are not familiar with them they are a small machine that has a digger blade on the rear end that looks like a super size chain saw blade. The size of trencher you would need depends upon how deep you need to put the line. (6" below your average frost depth).

If you live in a region where you only have a foot or 18" of frost they have a small walk behind unit that would do fine. If you need to go deeper they have larger models that are on four wheels and you ride it. Nearly all of the riders also have a small push blade on the opposite end for backfilling, and some even have a mini backhoe to dig the holes where the hydrants will be.

Here is a tip when renting machinery from your local tool rental company. Most of them charge a 1/2 day and a day rate, but if you rent the machine on a friday or saturday and have them deliver it to the site most of them do not deliver or pickup on weekends so they will drop it off Friday and pick it up Monday morning, but they only charge you for one day.

Oh, here is another tip. When buying your pipe, check out TSC (tractor supply company). They sell a lot of PE pipe for farm water lines & irrigation lines so they keep a good stock and generally their price is much better than what you will find in the big box home supply. They also have the hydrants and all the fittings for PE pipe.

Believe it or not, if you do the job with a moderate sized trencher one man should be able to complete your job in a single 8 or 10 hour day.

And one final hint while I am thinking about it. Sometimes getting a barb fitting in PE pipe can be a little bit of a challenge but their is trick to it. When your ready to install the fittings get a 5gal bucket of hot water and soak the end of the pipe a bit to soften it before inserting the fitting.

You will also need pea gravel to bed the hydrants in the bottom of the mounting holes. The pea gravel allows the water in the riser to drain out when the hydrant is closed so the riser won't freeze. They generally recommend making the hole about 2' in diameter and 2' deep than the hydrant position. You fill the hole with pea gravel up to the hydrant valve position, set the hydrant and add a bit more pea gravel, then I would cover the pea gravel with 6mil poly to prevent soil from working down and clogging the pea gravel, then backfill normally.

    Bookmark   May 18, 2012 at 4:19PM
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wow pup. thanks for all the info.very helpful. I have to tell you I totally agree with not attempting a hand dig.I'm 62 yrs young and I finally learned about my limitations. We actually do own a Massey Back hoe with a 12" wide bucket. We have very rocky ground here and digging isn't easy. The Massey makes short work of it all though with a 53 hp Perkins diesel engine. Actually I was looking at the PE hose at Tractor supply, seems very reasonable in price. Do you think running 2 separate 1" inch lines is an option? Plenty of room in a 12" wide trench. Also because of the rock, what is the best way to protect the plastic pipe?

    Bookmark   May 18, 2012 at 4:35PM
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If you run two separate lines the volume of flow in each line is then 5gpm and the FHL in 1" pipe @ 5gpm is 1.72psi.

That would yeild a 1.72psi drop to the hydrant and 3psi drop to the barn, but both of those drops should prove to be okay.

I forgot to mention we also have to consider VSH (vertical static head). If the line is running level VSH is not a factor but if there is any significant change in elevation from the source to the load we have to also add or subtract VSH at 0.434psi per vertical foot.

By example, if your barn is on a hill and it is 10' lower than the source you would gain 4.34psi, whereas if it was 10' higher than the source you would loose 4.43psi in addition to the FHL loss.

PE pipe is fairly tollerant of rocky soil, however they recommend that you bed it with 4" of sand, then put a 4" to 6" of sand over the pipe before backfilling.

You can be sure that back in my apprenticeship days I hand dug miles of trenches, but once I turned out as a Journeyman it didn't take me long to teach a new apprentice how to use a shovel.....LOL

When I retired the first thing I did was give my shovel away.

    Bookmark   May 18, 2012 at 5:15PM
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