Another Insulated Pex Question

http://www.ebay.com/itm/OUTDOOR-WOO...171?pt=LH_DefaultDomain_0&hash=item5ae24583c3

Does anyone know anything about the pipe in the above ebay listing. It appears to be better than the wrapped pipe. I have read about the problems associated with the wrapped pex inside the cooragated pipe. The price per foot of the above seems hard to beat for what it appears you are getting. Thanks in advance for any help on this.

From the pictures it looks like it's got to be a lot better than the bubble-wrap type but R16 from water to soil is a stretch.

The insulation looks thin between pex and black pipe. Looks like more insulation between the 2 pieces of pex than the outside. I think you could buy pex and have it sprayed in trench or DIY with Tiger foam type kit for less cash and have better results.

i have a guy thats going to do mine this week using 6" coragated with a slit cut it the top,1 1/4 oxy barrrier & closed cell foam. 1600.00 for 150 ft

Fill us in on how he keeps the pex in the center of the tubing while he foams it.

Welcome to the forum wrh51,
One of the reasons this type of pex insulation is better than the bubble wrap is the foam prevents air flow in the large pipe (which can easily happen if the ends aren't sealed) just from the fact that you have a large pipe in the ground with a lot of open air space. Air flow is only one of the reasons but it is really important. Bubble wraps that leave an open pocket next to the pex can make a wind tunnel that allows air circulation in the big pipe and that means lost btu's sometimes evidenced by a melt line but better defined with guages at each end of the tube. Simple closed cell that wraps the individual pex is much better but still allows for convection loss in the ground because of air flow and closed cell that fills the tube and prevents air flow is best. There is a potential for lost btu's if there is a thin barrier of foam between the pex and the large tube as seen in the link but it will have to run for a distance to have an appreciable effect because the actual loss is from infra red radiation more than direct convection.

If your pex is leaning up against the side of the conduit after foaming and the assembly is in moist earth there would be a tremendous loss due to conduction.

Does "infra red" mean radiation? Looks like we've covered about all types of heat transfer! ;-)

Fred 61,

You were curious about how to keep lines seperated during foam in place. Attached is a photo of my lineset, which was a 55' run underground. I did not use corrugated pipe, but maybe this will help. I used Tenman's method for foam in place, with a couple of modifications. I used 2" foam boards cut to 11" squares. I then drilled 1-1/8" holes in a pattern so that I could run 4 oxygen barrier pex lines (red), a domestic water line (white) and a low voltage conduit line (black polyethylene). I set the spacer boards about 4 feet apart, and it worked nicely to keep the spacing between the lines consistent. You can also see some steps that I put over the lines in the foreground of the photo. I cut three 8 foot 2x8s into 12" lengths. I nailed them together in sets of three to make several steps, which the foam contractor could easily walk on, as the lines were set in the trench before he arrived. The foam contractor simply picked each step as he went, and leap-frogged them down the line. The foaming process took about 15 minutes for 55 feet.

Well done! Well worth the extra effort. Can't fail. How would that have been done within a pipe?

Looks great Boomer! I'm not sure about the plastic though. Was it hard to thread all those pipes through the foam boards? I think your method is far superior to anything involving corrugated drain tube. I wouldn't waste my time with that stuff. I just had two 1 1/2" pex lines and the spray man used his feet to hold them about 3" off the ground while he foam under them, then he foamed around them but I know the distance between the lines varied from time to time but at least they didn't touch. I'm sure he got at least 3" on the outer sides of the pex and probably a lot more in some locations. He didn't measure how much foam he used and the owner bid the job over the phone based on "insulating two 1 1/2" lines 350 feet long". They had never done this on a residentual job but had done something similar for a big commercial job for Kiewit so they at least knew what I has talking about. If I was using a DIY kit I think the foam boards would help reduce the amount of spray foam and help keep things uniform. When water gets through the plastic, which would be hard to prevent, won't it just be that much harder for it to drain?

The plastic is installed only to keep dirt out of the foam during installation, which the contractor insisted upon. They had done projects like this before, so I did as they asked. The foam we used was closed cell, which is impervious to water. I folded the plastic over the top before covering it with dirt, so I dont think the plastic will fill up with water. Seems like the pressure of the dirt will make it difficult for much water to get between the plastic and the foam, which would not be much different than the damp soil being in contact with the foam.

I spec'd out the Tiger Foam and found that the $750 kit (price includes shipping) would be just barely enough foam for my project. The contractor I hired quoted the same price, and they did it for me while I watched and marvelled. They also brought with them years of experience, and a guarantee that there would be more than enough foam for the job.

Threading the pipes through the foam boards was not too difficult, mostly just time consuming. It helps to use a template to drill the holes, so that the holes for each line are all in the exact same place. This allows you to thread a couple of boards at a time. I also sprayed the pipes with water to lubricate them, and let them sit out in the yard in the sunshine to soften/loosen them up a bit. Once I had the boards in place the lineset became a massive unit, much like a serpent. It was a two person job to get it in the trench. I had to have a date nailed down with my contractor, because once I had the lines and plastic in the trench, rain would have filled it like a swimming pool. I lucked out and the forecasted rain never came.

Thanks for the help and info. I have read a ton about pex piping on multiple forums and manufacturer websites. I have written off the "wrapped" pipe completely. I have looked at various types that are like the one on the ebay listing. I think I have settled on getting this: http://www.thermopex.com/ . I have found a local dealer which gives me a better comfort level than dealing with someone out of state. Cost is $12.50 per foot which is a little more than the ebay listing BUT I don't need 150 feet so I will spend less overall. I did the math on doing it myself with spray in foam. I will be digging the ditch myself. I have my own excavator. Out of pocket costs are less but I have to consider the cost of my time. I am thinking 4-6 hours to dig, lay in the thermopex and backfill. Done. Doing it with pex and spray in foam and making jigs to seperate the pipe etc. - 10-12 hour day at best. So has anyone used thermopex before? Pros Cons other than what I have mentioned? Thanks!

BoomerJ,

Now that you have a heating season under your belt, how did the buried lines work out? I like the way you set up the lines with the foam boards. I am getting ready to bury my lines some time this month and I will probably copy parts of your idea? Woudl you change anything if you could? Any advice?

Thank you,

Bob

Have seen all of the i n ditch installs over the years, and this by far looks the best. We installed the microflex piping for a 155' run to house. For my info, all of you seem to take into account the loss of btus due to insulation and moisture. My concern was the fact that the pex expands 1" per 100' for every 10 degree rise in temp. Do any of you feel that the closed cell foam will be able to withstand this cycle (expansion/contraction) for and extended time frame without cracking open allowing ground water to penetrate?

Jamie

I used thermopex. Overall I like it and it does a good job. You dont get as much insulation as you could by foaming in place but my temp loss in 100' isn't noticable on my cheap gauges. I like that it is in a nice and tough casing.
It is kinda hard to bend and manuvure. If your going threw a cement wall you may want to peal the coating and foam off the part that will be in inside to make it easier to get threw the hole. You can insulate that part later.
Good luck. J.T.

wrh51, I'd stay away from that stuff. Either do like BoomerJ did, or a thermopex type of product. If you've gt to make tight turns, you'll have to foam in place.

Ahhh... One of my favorite topics. Hopefully ya'll've (that's southern for you've) read the latest posts on energy transfer performance in the Underground Sticky. I posted my documented DeltaT loss/ft based on our digital AZEL sensors. As hinted at above thermal energy "leaks" from our systems by one or all of three methods. Conduction (molecules touching something), Convection ( fluid molecules flowing by), or Radiation (infrared with no molecules at all involved)... The bubble stuff is inferior for each of those energy transfer paths to foam. After you've foamed you'll understand why worrying about sticking the our pex in corregated "protection" (in my experience) a waste of time and can lead to inferior insulation. Forget the protection and just blow an addition 1"-2" thickness around the lines if you're worried about rocks or traffic. That is a win-win. Boomerj's method for controlling spacing is clever, but as shown in the Sticky, I controlled our 3" line to line spacing within +/- .25-.50" just by holding the lines as the foam guy blew away. Not a criticism, it's beautiful, just really not necessary from a thermodynamic standpoint. Also, someone wondered about the issue of differential thermal expansion. That is the pex growing and the foam not (or visa versa). Yes, this will create huge shear forces at the bondline of the pex to the foam. So what may happen???? If those bondline shear forces exceed the adhesive strength of the pex to foam bond if will break leaving probably about a .00000001" clearance. For all practical purposed irrelevant considering ALL the other potential energy leak paths in our boiler world. That energy leak versus what I lose to IR radiation in my black iron lines is so far down in the total energy wasteage that "in the noise" isn't even accurate. So to summarize... resist the temptation think you MUST enclose the foam in SOMETHING. It could really hurt you. The only time I'd consider protection is if it was a high traffic area for heavy trucks. Precise line to line spacing is good but if kept to about 3" +/-1/2" you're still VERY good. As I said many times before, today, you just can't do better thermodynamically than the foam in place method. But for shorter runs the Thermopex products make cost/performance sense because the losses are small and the cost of getting a foam guy out for a small job is a big factor. Ain't no way anyone could have shipped to me two 1 1/4" lines encased in a 12"x12" block of closed cell foam about 150' long!! Best wishes and.... RESIST CORREGATION TEMPTATION! My new battle cry.

I hear ya'
I called the contractor and set up my appointment for the end of the month. I'm getting foamed for 90 feet and paying $12 a foot. Add that to the 1-1/4" hePEX plus (supply and return) at about $660, and I will be paying $1740. That works out to $19.33 a foot. Not bad.

I was going to do foam in trench. Both Boomerj and Tennman have provided a lot of great information on how to do this method correctly. However, I ended up doing 1 1/4 inch thermopex preinsulated pipe for my 100 ft. run from barn to the house. It is a great product. I paid $18/ft for the pipe. Least expensive local contractor for foam was $12/ft and the high quote was $30/ft. After figuring cost of the pipe and considering labor the thermopex was an easy choice.

This is a somewhat frustrating issue with the foaming in trench approach. In some locations these guys are like hen's teeth so quotes can make the products like Thermopex very cost attractive. Where we live there are several foam contractors so my price/foot was very attractive vs Thermopex. Either solution is excellent so cost becomes a major factor. As mentioned in the underground sticky, I got my foaming done for ~$5/ft vs your $12. So the price/ft varies radically based on availability of competitive quotes. Regardless, you'll be very pleased with the results. Since both products use the same polyurethane insulation, energy leakage performance comes down to foam thickness. At that point it's tough to beat doing it in the trench.