# Buried PEX



## Homerepairguy (Aug 1, 2010)

Although I've installed PEX water lines "inside" of our house, this will be the first time I'll be burying a PEX line. Note that it never freezes where I live.

I have a drip irrigation system where I have 3 anti-siphon valves mounted on a 2x4 that's attached to our fence. The water feeding those valves will come from our house via a 3/4 inch PEX line that will be buried. There will be no joints in the PEX underground and the PEX will just stick up from the ground on both ends. I need to shield the PEX from sunlight on both ends. 

There's a video on youtube that has the same situation where the buried PEX comes up from the ground and attaches to a pipe that goes into the house. The plumber puts black foam insulation on the PEX and it looks like the bottom end of the insulation will be buried. Here's a link to that video. See the 37 minute mark where he puts the insulation on the PEX:

 https://www.youtube.com/watch?v=_TIEou9dAgU


My questions are:


Is that an accepted way to shield PEX from sunlight? Won't the foam insulation just deteriorate in a couple of years?
Doesn't PEX need a special type of insulation that won't deteriorate the PEX tubing?
Thanks,
HRG


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## SeniorSitizen (Sep 10, 2012)

Crimp AL foil around it and paint it blue.


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## rjniles (Feb 5, 2007)

Use black poly pipe rather than PEX.


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## Homerepairguy (Aug 1, 2010)

SeniorSitizen said:


> Crimp AL foil around it and paint it blue.


That's one option that I could use. Thanks.

Still wonder if using foam insulation like that shown in the video is an accepted method for shielding PEX tubing that comes up from the ground outdoors. If anyone knows, please post.

Thanks,
HRG


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## Homerepairguy (Aug 1, 2010)

rjniles said:


> Use black poly pipe rather than PEX.


Thanks for taking the time to post an alternate option. I have left over Wirsbo/Uponor ProPex from my home installation and I have the expansion rings and the expansion tool so I would like to use it up. Especially since I paid so much for the tool :wink:.

Thanks,
HRG


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## SeniorSitizen (Sep 10, 2012)

Homerepairguy said:


> That's one option that I could use. Thanks.
> 
> Still wonder if using foam insulation like that shown in the video is an accepted method for shielding PEX tubing that comes up from the ground outdoors. If anyone knows, please post.
> 
> ...


The foam insulation I put around the suction line on my A/C condenser deteriorates exposed to afternoon sun 3-4 hours/summer day. Although I've never put a time on the amount of deterioration. Are there any difference in quality ratings as most products seem to have? IDK


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## Homerepairguy (Aug 1, 2010)

SeniorSitizen said:


> The foam insulation I put around the suction line on my A/C condenser deteriorates exposed to afternoon sun 3-4 hours/summer day. Although I've never put a time on the amount of deterioration.


Thanks for that info. I suspected as much.



> Are there any difference in quality ratings as most products seem to have? IDK


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## Thurman (Feb 9, 2009)

This post is basically about one of the problems I have with local codes. PEX is NOT allowed to be buried underground for anything--nothing. The black poly tubing (polyethylene) normally associated with incoming water lines and/or lawn sprinkler systems is allowed to be buried locally. I'm the type that when I want an answer I go to the place to get an answer so I went to the local code office to get and answer as to why PEX cannot be buried and black poly line can be. Ready? According to a local code official/inspector: "We have a lot of red clay soil in this area and PEX will not stand up to this type of soil if buried. The red clay soil will rub a hole in the PEX if it directly buried within the soil. The use of PEX as an underground water feeder is permissible only IF the PEX is contained within another approved type of covering, such as installed within PVC conduit or piping. The poly has a history of not having the holes rubbed in it with direct burial within this area". Go figure. ~


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## Homerepairguy (Aug 1, 2010)

Thurman said:


> This post is basically about one of the problems I have with local codes. PEX is NOT allowed to be buried underground for anything--nothing. The black poly tubing (polyethylene) normally associated with incoming water lines and/or lawn sprinkler systems is allowed to be buried locally. I'm the type that when I want an answer I go to the place to get an answer so I went to the local code office to get and answer as to why PEX cannot be buried and black poly line can be. Ready? According to a local code official/inspector: "We have a lot of red clay soil in this area and PEX will not stand up to this type of soil if buried. The red clay soil will rub a hole in the PEX if it directly buried within the soil. The use of PEX as an underground water feeder is permissible only IF the PEX is contained within another approved type of covering, such as installed within PVC conduit or piping. The poly has a history of not having the holes rubbed in it with direct burial within this area". Go figure. ~


The buried run for my project is only about 8 feet. I will be putting yellowish sand below and above the PEX line. One for protection against rocks, and two for a warning indicator if anyone digs the ground. It's just a short run.

Thanks,
HRG


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## Daniel Holzman (Mar 10, 2009)

I have often wondered why High Density Polyethylene (HDPE) is commonly used for direct underground bural, while PEX (cross linked polyethylene) is often not permitted to be used for direct burial. I have heard numerous theories, none very convincing. The idea that buried plastic pipe will "rub holes" due to movement seems dubious. PEX itself is chemically virtually inert, and does not interact with any commonly used insulation material that I am familiar with. Note that SupplyHouse.com (a supplier of PEX) believes that direct burial of PEX is permissible, however they note that local rules always apply http://blog.supplyhouse.com/direct-burial-of-pex-tubing/.

It is certainly true that PEX deteriorates when exposed to sunlight, however HDPE does also, unless treated with special stabilizers. HDPE is not so far as I understand any stronger or more resistant to scratching, and if the pipe is sliding or shifting around underground, there is something wrong with the installation. For my two bits, I would have absolutely no hesitation about burying PEX for a non-critical application like irrigation, but as always, check with your local code official first. As for the sunlight problem, wrap the PEX in any sunlight resistant material, or enclose the part of the PEX above ground in a sacrificial tube of PVC.


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## Homerepairguy (Aug 1, 2010)

Daniel Holzman said:


> I have often wondered why High Density Polyethylene (HDPE) is commonly used for direct underground bural, while PEX (cross linked polyethylene) is often not permitted to be used for direct burial. I have heard numerous theories, none very convincing. The idea that buried plastic pipe will "rub holes" due to movement seems dubious. PEX itself is chemically virtually inert, and does not interact with any commonly used insulation material that I am familiar with. Note that SupplyHouse.com (a supplier of PEX) believes that direct burial of PEX is permissible, however they note that local rules always apply http://blog.supplyhouse.com/direct-burial-of-pex-tubing/.
> 
> It is certainly true that PEX deteriorates when exposed to sunlight, however HDPE does also, unless treated with special stabilizers. HDPE is not so far as I understand any stronger or more resistant to scratching, and if the pipe is sliding or shifting around underground, there is something wrong with the installation. For my two bits, I would have absolutely no hesitation about burying PEX for a non-critical application like irrigation, but as always, check with your local code official first. As for the sunlight problem, wrap the PEX in any sunlight resistant material, or enclose the part of the PEX above ground in a sacrificial tube of PVC.


We are both on the same page.

I primarily wondered if protecting PEX outdoors using the foam insulation as shown in the video is an accepted method. But from the responses so far, I'm not going to use the foam insulation method and go with what you said in your last sentence.

Thanks,
HRG


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## SeniorSitizen (Sep 10, 2012)

About 50 years ago we quit using black poly pipe on the farm because of Gophers chewing holes in it. Whether it has been chemically improved to prevent that problem IDK. In other words, a Gopher rubbed a hole in it.

It's now used mostly as a protective sleeve for other tubing such as the under slab plumbing of my house. Makes re-plumbing a snap if that ever becomes necessary.

Some plumbing supplies keep long radius pvc riser sleeves for this purpose. May have other names also.


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## Ghostmaker (Mar 2, 2013)

Thurman said:


> This post is basically about one of the problems I have with local codes. PEX is NOT allowed to be buried underground for anything--nothing. The black poly tubing (polyethylene) normally associated with incoming water lines and/or lawn sprinkler systems is allowed to be buried locally. I'm the type that when I want an answer I go to the place to get an answer so I went to the local code office to get and answer as to why PEX cannot be buried and black poly line can be. Ready? According to a local code official/inspector: "We have a lot of red clay soil in this area and PEX will not stand up to this type of soil if buried. The red clay soil will rub a hole in the PEX if it directly buried within the soil. The use of PEX as an underground water feeder is permissible only IF the PEX is contained within another approved type of covering, such as installed within PVC conduit or piping. The poly has a history of not having the holes rubbed in it with direct burial within this area". Go figure. ~


That's news to me.. We been burying pex in Ohio since it's been a code approved material. And heating guys have been placing it underground even longer.

2 concerns with any plastic that is buried. Rocks are bad so bedding them completely in sand is a good idea then back fill. Sun is bad so you must use a plastic sleeve on that area.


Good vinyl electrical tape will also work.
http://plasticpipe.org/pdf/pex_designguide_residential_water_supply.pdf


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## Homerepairguy (Aug 1, 2010)

Daniel Holzman said:


> ...snip...
> As for the sunlight problem, wrap the PEX in any sunlight resistant material, or enclose the part of the PEX above ground in a sacrificial tube of PVC.


I did the job yesterday. To protect the exposed PEX from sunlight I bought a length of 2-1/2 inch square plastic rain gutter downspout in dark brown. I ripped one side of the downspout lengthwise. Then I cut two lengths for both sides of the exposed PEX. Spread the downspouts apart and slipped them over the PEX tubing.

The top of the downspouts are well above the top of the PEX so very little indirect sunlight could affect the PEX tubing but I taped the tops with electrical tape anyway. Later I'll figure out a way to make plastic caps for the tops of the downspouts if the electrical tape starts to deteriorate.

A side benefit of using plastic downspout to shield the PEX from sunlight is that it also protects the PEX tubing from string trimmers and pets or rodents.

A tip if anyone else uses plastic downspouts to shield exposed PEX from sunlight:
When I ripped the downspout lengthwise, the downspout bends inward which caused the ripped sides to overlap about 1/4 inch. While this is a good thing to prevent sunlight from getting in, the bending force is fairly strong which made it rather difficult to spread the downspouts apart to slip them over the PEX tubing. After the job was done, I figured out that what I should have done was to make two "U" shaped handles out of wire clothes hangers. Then bend about 3/8" of the ends back. This would have allowed easily hooking the handles on the ripped ends and spreading the downspout apart. I'll make some handles if/when I need to remove the downspouts for maintenance.

Hope this helps someone,
HRG


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