# underground pex alternative?



## b33p3r (Sep 28, 2010)

I'll be putting in my under ground pex this week and since the cost of manufactured insulated pex is out of my reach($$) I came up with the following alternative for 1/2 the cost.
   2  1-1/4" pex with foam pipe insulation around each individually,  pulled through 4" sch 40 pvc pipe. The 4" PVC will be inside 6" sch 40 PVC. In between the 4" and 6" pipe will be great stuff expnded foam. All this will be laid on top of 12" of gravel, pitch to drain water away to daylight(Gravel is left over from another project). All joints will be glues and I'll also apply some silicon caulk to the outside of the seams of the couplers and such. I'll also cover all piping with a thick mill plastic to get any water down to gravel bed before meeting the PVC. It's a straight 75' shot so only one elbow up to boiler shed.
  This is costing me half of buying pre-insulated pipe. It also allows me to pull new lines through the 4" pipe should I ever need to. I'll also pull under ground wire through same 4" pipe for electric + a pull string for future needs.
  I'll let everyone know how this worked come spring next year but thoughts are appreciated.


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## juddspaintballs (Sep 28, 2010)

How are you going to spray cans of Great Stuff 5' deep in between the 4 and 6" PVC (10' long sections, 5' is the distance from each end to the center)?


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## goosegunner (Sep 28, 2010)

Have you looked at the price of 4 and 6" pvc lately?

6" is over $20 for a 10' piece here.


gg


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## b33p3r (Sep 29, 2010)

6"    $20.00 for 10 ft = $2.00 p/foot
4"    $11.00 for 10 Ft = $1.00 p/foot throw in the couplings and such and your at about $6.00 p/foot.
I'll post the total when I'm done.
    I plan on drilling holes just big enough to insert the straw from cans. After I do the first hole I'll let it expand and then determine the spacing of the spray holes. I plan on doing a 10 ft section at a time.


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## leaddog (Sep 29, 2010)

Have you priced out having it sprayed with foam. It would be faster and have more insulating value. Around here you can get it done for about $6-8ft.
leaddog


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## heaterman (Sep 29, 2010)

How are you going to suspend the 4" inside the 6" to get insulation all the way around it?
How did you arrive at the number of cans of great stuff needed to do the job?


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## rkusek (Sep 29, 2010)

I was thinking the same thing when I read your post.  Your wasting your time and money.  Find a spray insulation contractor that will spray the pex directly in the trench.  I bet you can find someone that will cost less that what this is going to cost you.


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## goosegunner (Sep 29, 2010)

huskers said:
			
		

> I was thinking the same thing when I read your post.  Your wasting your time and money.  Find a spray insulation contractor that will spray the pex directly in the trench.  I bet you can find someone that will cost less that what this is going to cost you.



True

I had a guy lined up to do 130' for $600. I ended up going with the logstor because of timing with the excavator and the foamer. My trench was deep for a water line and I didn't want to take the chance on cave in while waiting several days for the foamer. Thought about backfilling a little but thought settling under the foam would be bad.

gg


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## b33p3r (Sep 29, 2010)

The price for the spray in foam I got was...you ready for this....$900.00 for 75 feet! Thus the alternative method. I'm not sure how many cans I'll use yet. I have to do the first test spray to see what the coverage is. I'll get back to you on that one. I'll cut a wood disk to support the 4' pipe until the foam stiffens up and holds it . Then move it to the next section.


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## Tony H (Sep 29, 2010)

Using sections of pipe is sometimes a problem even with glue and proper assembly the frost heaving will often pull the pipes apart. You would be much better off to use roll pipe and tubing with no external joints. Another thought would be to use roll pipe made for water lines to run your AC wire and aa spare tube for future, it's a code violation to run AC in the same tube as water. You might not get tagged for it now if you have no permits but it could cause you trouble when selling if the inspector notices it.


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## sgrenier35 (Sep 29, 2010)

Are you doing 1 sleeve for each pipe?  If not you probably won't get 2 -1 1/4" pex with insulation on each one through the 4 " pipe.


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## b33p3r (Sep 29, 2010)

Tony H you are a wise man. I never gave the electric in the same pipe as the water a second thought! Thank You. At this point I have no intentions of selling the house but who knows............point taken. As far as frost heave goes..I'm burying the lines below the frost footer so frost heave won't be an issue. 
   I already have a 10' section of 4" pipe and the 2  1-1/4" pipes with foam does fit with a little room to spare. Very little, but room to spare.
  The only thing I haven't tested yet is how far a can of spray foam will expand between the 2 pipes. That test will be done within the next 7 days. I'll post back with the results.


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## Tennman (Sep 29, 2010)

Lots of "been there done that" guys sounding the alarm for you. I don't have enough time to discuss all the issues with your approach. Ask goosegunner where he bought Logstor of the right length. Otherwise I wish you well... read the underground sticky about where not to save money. Your approach and motivations are remarkably similar to my disaster. I'd like to know how much your saving vs buying Logstor cut to length.


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## woodsmaster (Sep 30, 2010)

Expanshion and contraction can also pull the joints apart. thats why sewer pipe has a rubber gasket and is not glued.


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## b33p3r (Sep 30, 2010)

Tennman, 
                    I'm not ignoring the alarms. I'm actually trying to sound them. I haven't seen anyone here do a pipe in pipe install. Yes I'd like to save money whenever I can but not at the cost of quality. I'm throwing this out to get people to tell me why it won't work. I know after thinking this through that there is something I could be missing. Woodmaster just gave me the first reason why it's probably not a good idea!


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## Tennman (Sep 30, 2010)

Sorry, the two sentences "I’ll let everyone know how this worked come spring" and "I’ll post back with the results" implied to me your course was set. I'll take a minute since I was time crunched on my last reply. I used the same insulation sleeves. I had to dig up that first home brew system I tried which bore remarkable similarity to your idea. In the beginning your approach will provide better water protection than what I thot was water impervious but later proven to have many pinholes allowing water ingress. My first season boiler exit temps were good but measuring my HX inlet temps provided the hard data that my homebrew insulated lines sucked.... big time. Last Spring a blew ALOT of money to dig up and redo. The sleeves that where not filled with water and saturated like a sponge at our kitchen sink were locally flattened apparently from just the weight of the lines with water. Very poor to no insulation at least on one side. Obviously those sections not water saturated were lousy insulators because the properties were poor. The inside of your PVC cavity will be nice and warm... what does that tell you? I used Tigerfoam thinking where I drilled holes it would expand down the tube. NOPE. And even if I drilled LOTS of holes how would I keep the lines centered so the Tigerfoam expanded uniformly around the sleeves. Well after about 30 frustrating minutes I said screw it this is good enough. WRONG. Bottomline IF/WHEN those sleeves get wet you're screwed and mostly if they don't get wet you're still screwed. I could share more but really out of time. Ok, I gotta go make money. I may just add this rant onto the end of the sticky because this is about the 5th time I've typed it. I'll ask permission first.


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## b33p3r (Sep 30, 2010)

Tennman,
               I understand your frustration with the original install and I truly do thank you for the warnings. However, you never mentioned exactly how you installed your original piping? Was it pipe in pipe with foam in between or was it single 4" pvc pipe ?  Can you tell me details about your original install?
               I want to get my pipe in ditch real soon for obvious climate reasons but I have not bought the PVC pipe yet. I have gone to lowes and made sure a 4" elbow will fit within a 6" elbow.  My neighbor will be digging my ditch with his Kabota and he will show up when it's convenient for him, not me as it should be.
               One of my personality flaws is I won't take can't for an answer. I need to know why. I hope this doesn't irritate any one on this forum I just can't accept something without a reason. That's why I threw out my ideas prior to installing. A coworker of mine started asking me what I was trying to do with the under ground piping. After describing to him what I was proposing he said that is how they used to do it in the military. The only thing he added was they would spray foam the couplers of the outside pipe and wrap in plastic type material.
               From what I can gather from your post is you ran a single PVC pipe and pulled your pex through it. You then drilled holes in that PVC and tried to fill it with foam trying to surround your pex? Yes?
               What I'm proposing is running a 4" PVC pipe,sch 40. Within this pipe will be my 2   1-1/4" pex lines. Each with foam pipe insulation wrapped around each(like the piping foam you get from lowes/home depot).  Then I will slide 6" PVC sch 40 over the 4" PVC piping. I will then drill holes in the outer most 6" PVC (without compromising the inner 4" PVC pipe)  to shoot great stuff expanding foam with all intentions of filling the gap between the 4" and 6" pipe. I plane on siliconing all coupling seams on both pipes and after talking to my co-worker I might as well surround all 6" couplers with foam. This will all be laid on a 6-12" bed of gravel to daylight. It will also be covered in a thick mill plastic so water hits the gravel before it hits the PVC.
                I'm confident  I can do this for less than I can buy logstor for. The plus to my idea is I can still pull new pex lines  if needed. With Logstor you have to dig it back up. I really want to know about your original install that failed so I don't run into the same problems. But please give the details of your original install so we can learn from mistakes.


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## parkini (Sep 30, 2010)

I think you can save yourself a lot of headache and money if you just insulate the lines in the trench without all of the PVC and foam pipe wrap.  I just ordered a tiger foam kit and sprayed the lines in.  The process goes very quick and is very sound.  I was able to run two 1" lines and two 3/4" inch lines for 14.00 a foot.  Logstore would have cost me 24.00 a foot because of the dual run.


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## Tennman (Sep 30, 2010)

BINGO on what parkini said


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## slowzuki (Sep 30, 2010)

The lines need to have good insulation from each other and from the soil.  The return line from the house will "cool" the incoming line.  The large diameter of the 6" pipe gives a nice big radiator surface to the soil, the fairly big 4" inside makes are darned good radiator from the inside lines to the insulation.

To be efficient, you want to insulate them from each other, and insulate them from the ground in the most compact ie least surface area and best insulating material you can.  The double pex in a pipe is one of the best ways to do this, foaming a trench is next.

A lot of people think if the ground doesn't melt over their pipe they did a good job, there is more to it than this as the ground can absorb massive amounts of heat if the pipe is buried at any depth.

Also, people will look at the outgoing and return temp and say, hey I'm not losing much but really they are seeing the return water heated by the outgoing.  Need to check the drop from heat source to house on both lines, and the drop while in the house, to get an idea of where all the heat is going.


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## Willman (Oct 1, 2010)

Can foam (single component) needs air to cure. I have cut thru cured foam into uncured foam in a previously confined space. A rocker panel on a car. The bonehead who filled it should have used 2 component foam. The foam then grew like it was just sprayed. This is how it remains a liquid in the can.This after a prolonged period of time.  A better approach would be to use a pourable 2K foam. Calculate the space and mix and pour in. 2 component has a higher r value as well as being stronger. 

Will


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## slowzuki (Oct 1, 2010)

Actually just needs moisture.  Normally air carries that moisture in, so he must have fixed the rocker pretty well!


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## Willman (Oct 2, 2010)

> Actually just needs moisture.  Normally air carries that moisture in,



When the can foam expands it hardens/cures from outside in. A big enough area will allow the foam to remain uncured in the center. Once cut away it will start expanding again. It was unreal watching it grow after a couple of months in the rocker. I figure the can foam inside a glued up pvc pipe of the length  needed here would not cure fully and in turn would not offer the full r value. 

Anyone know what the r value is on can single component foam is ?

I have seen foam board used for a 3 sided trench with the spray foam sprayed inside. The foam guys like to have a defined area for an accurate quote. Just trench spraying would prolly initiate a high bid to cover their material use.

I think a 2 pipe pvc chase would negate the heat loss between supply and return and still allow future service.

Will


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## breklaw (Oct 2, 2010)

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Something we have learned over the years is that you can't lay pipe directly on gravel. It must be surrounded by 6" sand on all sides, OVER gravel. Rocks move, pipes move, and they will find and pierce your pipe. We have seen this with thick galvanized pipe many times. How about  2 4" pvc pipe spray foamed in? Seperate supply and return, well insulated, and easily replaced.
Bill


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## juddspaintballs (Oct 4, 2010)

parkini said:
			
		

> I think you can save yourself a lot of headache and money if you just insulate the lines in the trench without all of the PVC and foam pipe wrap.  I just ordered a tiger foam kit and sprayed the lines in.  The process goes very quick and is very sound.  I was able to run two 1" lines and two 3/4" inch lines for 14.00 a foot.  Logstore would have cost me 24.00 a foot because of the dual run.



How many feet did you end up running?  I might go with a TigerFoam kit if I get a high estimate for my run.


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