Underground lines - not the place to skimp!

[Vizsla]

I know its an old post, but the zpipe is good for snowmelt applications in your yard/lawn. Ask owners not the salesman. There are several Michigan customers that did the foam trench with. The pipe, or replaced it after a season of seeing how it performed. 127' run to HX, boiler supply 176-188, never could get higher than 168 to the HE, at 6-7 GPM. Wet, low ground, bad conditions during winter didn't help. Driving the tractor or skid steer over it was a no go.

 

[Procyrus]

Hello I am new to the forum and have been doing lots of research on how to do my underground lines. I almost made the mistake months ago and bought that crap wrap that ebay sells. A few of my friends have used the closed cell foam spray; one using a contractor and one using a kit. I really like cjdave's method and was wondering if he has any problems with the installation since he has done it. I dont have to worry about tree roots or anything but it will be going under a driveway that accommodates lighter vehicles. I reside in northeast ohio and I have nothing but clay to dig into. I plan on renting a backhoe and dig about 3 to 4 feet deep, line it with 6 mil plastic, then 2" xps foam board, and filling it up with touch 'n seal U2-600, pretty much how cjdave has done.

Any thoughts, suggestions? Thank you.

 

[Tennman]

Please, no offense to Dave, but I fail to see the benefit of the blue foam. Lining the trench with plastic or not using the plastic allows the dirt to serve as your mold. Coefficient of Thermal Conductivity for XPS ~.035-.045; for Polyurethane blown foam ~.01-.013 per the manufacturers data. The lower the number the better the insulator or XPS is about 1/3 as good as polyurethane. My experience is XPS in the weather it absorbs water, but maybe not true for all types. So if it's easier and a better insulator I don't see why you wouldn't just blow all closed cell polyurethane. Maybe I'm missing something, but the thicker the polyurethane the better the thermal efficiency. If you go the Tiger foam route, depending on the length of your run, you'll need a bunch of those small $600 kits. If U2-600 is a closed cell polyurethane it should work. I just don't see the advantage of messing with the boards particularly if they absorb water.

 

[Procyrus]

They do make the foam boards closed cell. I can get 3" thick 4x8 sheets for $15 a piece from a local guy. After I cut up those sheets and make a trough out of them, no more than 12" in width, all I do is lay the pipe and spray the 80' length. Giving that those 600 kits cover 600 board feet, and I have an 80' length to fill, I will only use 240' of that spray to fill 3"over the pipe. I think 3 inches covering all sides of the pipes will be ample, almost a 6" diameter. The foam pieces will be fused/sealed together with the spray foam. As cheap as those boards are, much cheaper than the spray foam, I could figure out a way to router the sheets to sandwich in the pex, and eliminate the spray, but I need the spray to fuse the foam boards together. And with the almost half of the 600 kit left over, I need that to seal in some areas around the boiler and parts of the house/shop. I will be doing this project in a week and will take pictures as I go.

If I didnt use the foam boards as a trough, I would need an extra 600 spray kit. They sell them on ebay for $636, the foam boards will run me about $75. Thats the difference in savings.

Doing it this way is still costing me about $1,000. But its better than the crap I almost bought, the 3 and 5 layer junk.

Dave has also let me know that he hasnt had any issues since his install.

 

[shawntitan]

They do make the foam boards closed cell. I can get 3" thick 4x8 sheets for $15 a piece from a local guy. After I cut up those sheets and make a trough out of them, no more than 12" in width, all I do is lay the pipe and spray the 80' length. Giving that those 600 kits cover 600 board feet, and I have an 80' length to fill, I will only use 240' of that spray to fill 3"over the pipe. I think 3 inches covering all sides of the pipes will be ample, almost a 6" diameter. The foam pieces will be fused/sealed together with the spray foam. As cheap as those boards are, much cheaper than the spray foam, I could figure out a way to router the sheets to sandwich in the pex, and eliminate the spray, but I need the spray to fuse the foam boards together. And with the almost half of the 600 kit left over, I need that to seal in some areas around the boiler and parts of the house/shop. I will be doing this project in a week and will take pictures as I go.

If I didnt use the foam boards as a trough, I would need an extra 600 spray kit. They sell them on ebay for $636, the foam boards will run me about $75. Thats the difference in savings.

Doing it this way is still costing me about $1,000. But its better than the crap I almost bought, the 3 and 5 layer junk.

Dave has also let me know that he hasnt had any issues since his install.

I used a 600 board foot Tiger Foam kit and came out short...
https://www.hearth.com/talk/threads/tiger-foam-let-me-down.21395/
No problems with temp loss, or the application, just a heads up that it didn't give me as much as I expected.

 

[The Weimar]

Hi Guys, the higher quality the insulation and the more air space that you can create underground will greatly increase the insulative abilties of your installation. I used the german made insulated pex that has the pex nicely spaced and insulated with a very dense foam, and I pulled it through a 6 inch PVC conduit that will help if I ever have to work on it, and adds another layer of protection and Insulation. The stuff that is wrapped with insulation works, but there is better stuff available. Not cheap by any stretch....

The Weimar'

 

[Procyrus]

I finally completed my project, did it just like Dave but changed a couple things around.

1. I used 1 1/2" XPS foam boards and made troughs out of them, in 4 foot lengths and 4 inches in height, I used the small cans of spray foam to assemble them. The foam acts as a sealant and an adhesive.
2. The 1" O2 barrier pex lines are a pain to deal with, even letting them warm up in the sun on a 70 degree day did nothing, so I tied a weight to then end of each one and stretched them out as far as a could to help straighten them. After a week of this they still had "memory" and coiled back up some. To separate the 2 lines i cut XPS foam into 2" strips and zip tied them together, that helped out a lot.
3. I used 10" spikes and nailed through the 2" strips, between the 2 main lines, through the troughs into the ground to center everything and to hold them in place.
4. I then zip tied the water supply line to the return line. You will see 3 lines in the photo, the supply (blue), the return and main (red). The main line is not touching anything to ensure minimal temperature loss.
5. It was 55 degrees and sunny yesterday. The touch n seal u2-600 needs to operate between 70 and 90 degrees. I stored the 2 tanks in a room with an electric heater for 3 days at 85 degrees. It is critical to keep the tanks warm before operating them. As soon as I was ready I took the tanks out, hopped in the trench and started spraying. My neighbor moved the tanks as I was spraying. I took 3 passes on everything. Its an 80 foot trench and the troughs are 4" deep. You have a 30 second window before the nozzle starts drying, but they give you plenty of nozzles. You can not spray 4 inches at once, they advise you to make passes. They were correct because I noticed if I tried to spray a second layer on right away it blew the first layer off. This stuff dries in 30 seconds.
6. The troughs did save me on a few things, to make sure the lines were centered, to hold everything down, and to minimize on the spray foam. The sections of trough should be close together as possible but the ends don't need to be glued, I had a couple turns and pitches to make. The foam kit sealed everything together.

I had to do it this way because I could not get a spray foam contractor to come out, nobody would return my calls or emails. The pex lines, the xps boards, the foam kit, and other misc items came out to about $1,100. I was able to insulate the lines, parts of the boiler, and I have about 1/4 left in the tanks to do some areas in the basement. Doing it this way I was able to run a new water supply line to the shop that will be used for the boiler as well. The boiler has a float in the top that will automatically turn the water on and off as needed, just like a toilet tank. Down the road a may get a sealed system, which is why I bought the oxygen barrier lines.

I am very happy how everything turned out. I would highly recommend this kit, covers 600 linear feet and is easy to work with. Much thanks to Dave and to my neighbor who sold me the boiler and helped me as well.

 

[shawntitan]

I had to do it this way because I could not get a spray foam contractor to come out, nobody would return my calls or emails.

I had the same problem, LOL... Those guys must be busy... Maybe I should l look into starting a spray foam business...

 

[varadhammo]

I have some 5-wrap z-supply line in the trench already, luckily it's not all backfilled yet, the part that is is easy enough to dig up. I decided to spray foam it, and I had a guy come out and do an estimate for foaming around the 6" corrugated in the trench (~90' each way)

I had him do a bid for spraying just the sides and top (2") and also a separate number for doing 2" underneath the corrugated, which added another ~70% to the cost.

My thinking is that foaming underneath is not as important as sides & top, since it's already waterproof and has some insulation and air space in the pipe. Is it worth the added price to foam underneath it as well, or am I getting into diminishing returns?

 

[Wood-row Wilson]

Although not completely finished, I thought I would report on my foam-in-trench project coming to completion. I ordered the Green Foam it 602 board feet closed cell spray foam and was very happy with the instructions, supplies and the product itself. I took advantage of a rare 70 degree late October day here in Michigan to start the process. I won't spend a lot of time repeating much of what has been said already in this thread, but much of what I learned and how I deployed my plan is a result of the learning I've found through this and other threads. Here's a highlight of my day:

Was working with Pex B oxygen barrier tubing and with the combination of not having a straight run, it was tough to keep things separated. Back-hoe dug trench 24" wide, so I constructed the foam board trench as described a few times above. I was able to score 2.5" foam board which helped to beef up the total amount of insulation around the pipes. I drilled a 2" hole through the concrete slab in both my laundry room (water heater) for the first two lines and pole barn for the other end of the four lines. The 2 to the furnace go under the foundation and into the crawl space before the rest of the 50 run to the furnace. In total, 4 lines through the trough. Had the help of two others to keep the pex straight, move the foam canisters, and lay plastic over before quite quickly covering back up with dirt before the next day's rain. All in all, it went well but ended up 10 ft short for the <100 run. I may have been a bit liberal, but was happy with what I buried! Here are my biggest take-aways:

• Should have done more shopping on the foam. I was referred by a contractor that I contacted to go with the DIY kits and was referred to a local retailer that had the foam, but ended up ordering the Green Foam it Brand. I plan to purchase more foam through http://www.distributioninternational.com/. I called recently to get some pricing and found it was very competitive. Come to find, they have multiple locations. Don't hold me to these numbers, but here is what I received recently. Competitive to Foam it Green and Tiger foam, but in hindsight I should have called and purchased the 1000 board ft kit. Less than $100 for 400 more board ft! 200 board ft –$282.43, 300 board ft– $334.42, 400 -- $???, 600 board ft– $623.12, &1000 board ft– $717.90
• Should have taken more time to set the lines! It was tough to wrestle four lines to stay separated, get a good amount of insulation around each, while foaming. Many times I had to spray a bit and let it sit just to keep things straight. I wish I gave myself more time set the lines and go back to spray around them to keep things consistent.

I plan to purchase more foam to finish the insulation of the 10' of pex that's currently exposed at the end of the first run along with what is exposed in the crawl space to the furnace.




Thanks to all of those that contribute to this forum that helped make my install a (so far) reasonable success!

 

[runnerxc]

Any update on the foam underground applications? Have you experienced any more heat loss now that it has been a few years and everything has settled?

 

[Tennman]

Nope. No change in performance in 5 seasons. Make the foam as thick as you can afford. Assuming closed cell polyurethane foam the only way to improve R value is additional thickness. I'd guess past 3-4" all around (including between the tubes) the ROI starts to drop off rapidly. I have +3" on my storage tanks and they feel like the ambient.

 

[Greenfield Dave]

Ok, I have a question for the experts. Is there ANY way to insulate my underground piping without digging it up? I skimped on the install, mostly out of ignorance many years ago, (hadn't found this forum yet) and now I am losing waaaay to much heat. I buried the 3 wrap PEX in corrugated drain pipe about 30" down.

If I have to dig, I may just abandon the old piping and install new. And I WILL foam it in this time.

Any input is much appreciated..

 

[Tennman]

Nope.

 

[Pat32rf]

Nope.

While you have to dig, I would think that a small (compact tractor size) backhoe would let you reuse the pipe after you go to closed cell foam.

 

[adamant]

anyone have bad results with the insulated pex you see on e bay?

 

[Pat32rf]

anyone have bad results with the insulated pex you see on e bay?

 

[Pat32rf]

Never seen a poster claiming to have GOOD results. The opposite seems to be VERY common. Maybe if you are inb desert conditions or running overhead...

 

[maple1]

anyone have bad results with the insulated pex you see on e bay?

Post 76, up the page.

Don't know if it came from Ebay but likely the same type.

 

[Antman]

Pete, Yes, I used the plastic sheeting just to keep the process clean. After the foam is blown it serves no purpose. I just laid it up on the sides of the trench as shown in the pics and put rocks on it every 8-10'. Ok.... can't spend a lot of time on this but a quick look shows XPS thermal conductivity at .027-.03. Urethane foam at .021. Do some quick research on line like I just did and compare Heat Transfer Coefficient. Bottom line using the spray polyurethane is a better insulator so using the sheet stuff is a waste of time and money. No need for multiple trenches, since the electrical conduit doesn't care about temperature, you can do what I did, just lay on top of the cured foam and cover with dirt. So in summary, if you compare the material properties of what you intend to use, you'll most likely find the XPS is a poorer insulator (or a better heat transfer material) than the spray, closed cell, polyurethane.

BTW, my water round trip distance is about 440'. I am routinely seeing a 2*F delta from my AZEL temp sensor in the boiler room where my water enters my 1 1/4" Pex. After prolonged idle... yeah bad but.... I frequently see the deltaT close to less than 1*F (an unbelievely sometime less than 1*F). That is an amazing .22*F/100' of run. In review, my contractor that dug up my first "go cheap" attempt using those insulation sleeves had a 12" wide bucket. So my pex is in a block about 12"W x 10"deep. Far more than most need but it was a byproduct of carefully digging up my first attempt so I could reuse my pex (mission accomplished). If I knew how I'd post pics of my AZEL digital display to so the temps to document what I'm asserting. There ain't no way the off the shelf stuff can match my 12"x10" foam brick that I had sprayed. My underground is about 180' and I paid $700 or $800 to do the trench. All insulation done in about 30-40 minutes then recovered with dirt. I would guess the cost/performance crossover point for spraying in place vs the Thermopex type stuff is maybe when the underground gets in the 30'-40' range. At shorter underground distances the losses using a Thermopex type product probably wouldn't justify the expense of a foam contractor's minimum charge.

Thanks for your sticky on underground lines. I noticed you are in Southern Tennessee. I am installing a Garn in the Memphis area and have two long runs: a 250' run (500' primary loop) and a 300' run (600' primary loop). Do you know anyone who would help me out with closed-cell PUF in trench? If you are close by maybe I could get you to stop by some time or show me you setup?

 

[Tennman]

Thanks for your sticky on underground lines. I noticed you are in Southern Tennessee. I am installing a Garn in the Memphis area and have two long runs: a 250' run (500' primary loop) and a 300' run (600' primary loop). Do you know anyone who would help me out with closed-cell PUF in trench? If you are close by maybe I could get you to stop by some time or show me you setup?

Hey Antman, My SIL's name is Anthony and he goes by Ant. Can't help with local foam insulation contractors, but there has to be some in a city of Memphis' size. It appears your heating two buildings with one boiler. With runs that long I'd strongly consider 1 1/2" pex. Our underground is about 170' or a 340-380' round trip and I wish I'd have bit the bullet for 1 1/2" pex. I probably would have recovered the pex cost within several years in electricity savings resulting from a slower flow rate. Our home is a btu hog so we needed a pretty big pump due to the flow velocity to get to the gpm we needed. High velocity flow results in increased head due to wall resistance. You're welcome to visit to see our system, but need to schedule to make sure I'm not out of town. I added a thread about the "First Windhager in Tennessee". You'll see quite a few pictures of our system in that thread. I love using pellets, but the BioMass is still plumbed into our 1000 gal of storage so we can burn either wood or pellets. You can PM me if you have any questions. I'd be glad to run a quick calc of your gpm and head in my spreadsheet built from the Taco TD10 datasheet. Given those run lengths you'll save a ton of money doing foam in trench. Based on the foam on our storage tanks, it seems after 3.5-4" thick is diminishing return on thickness. But for underground I'd shoot for at least that much with at least 2-3" separation between the supply and return lines. PM if you have other questions, but with a system of your size I assume you're plugged in with an experienced installer.

 

[Pat32rf]

Well now I am wondering.....
Last November we did a quick and nasty install of a used P&M ML36 at our tenants house next door. Used an old chunk of either LogStar or Thermopex for the 15' run to the house, then connected a water/air radiator in the cold air furnace line and also a sidearm heater for water. They have been keeping the temp about 24C all winter, every few days I drop off about half face cord of wood in a skid. They keep the firebox of that P&M full, but most of it looks like charcoal as the fan only starts now and then..
This has worked so good that this summer I want to relocate the OWB over to our house and run pipe back to the tenant's, about 100' The boiler would be about forty feet from our place and I had planned on foaming these runs of PEX.
Most of the run however would be along our driveway which is built on native gravel. Each fall this gravel fills with water and then freezes and heaves about 6-8".
I expect that I would have to dig about 4' to get completely below the frost, even though the snow covered lawn only freezes 6" or so.
How deep do you normally plant this pipe? I have a feeling that the frost will not hurt Thermopex or similar pipe, but I worry about a DIY foam trench...
Our geothermal pipe to the lake is only about 2-3 feet down....

 

[jfriesner]

Here is my experience. I got this style pipe, not sure the brand, used from a friend, it was dug out of the ground from a previous install, and I reused it on my install. I have it running 65' from my boiler to the house. It is roughly 30" deep but surfaces by the house to enter into my furnace room through the exterior wall. As you can see snow sits on it and doesn't melt. The snow fell this morning, about 8 hours ago, and it still hasn't melted off of it. Yes I have boiler going and set at 180F. I also have a 15' section of the same stuff running directly on the ground to my hot tub. When nothing is calling for heat I have a 4 degree difference between supply/return at the boiler. My loop is about 300' round trip. The stuff is amazing and definitely worth what you pay.

Also wanted to add I live in north central MN where we've already been below zero this winter.

 

[Potsdam]

 

[Potsdam]

Cheap and easy without over thinking much. 75 ft run from garage boiler room to an old 1880's house. dug 2-1/2 ft deep with (1) 2" blue board on the bottom and the rest as seen. All 1-1/4 heat pex insulated with standard pipe insulation inserted in water / sewer PVC glued. Ran the low voltage and 120v lines in between and electrical conduit for future needs above blue board to connect house and boiler controls. Had to make room for pex expansion in house and garage before copper runs. Solid build with no heat losses to ground. Boiler makes 180F and house receives 180F. I don't grow grass in the winter . Only regret is not heating the Water/Sewer PVC and bend verses using 45's. this is the spot I worry about year after year with the expansion/contraction. To reduce effects, the loop from the garage to house circ pump runs 100% of the time as long as the boiler is above 140F.
The reason I did this approach was witness to the failure of the highly marketed insulated supply and return pex on the market that costs runs of about $15 foot. Poor customer lost so much heat to the ground and return flows , he grew grass and burned more wood than heat his home.