Digging the grave

[sjfrench]

Advice needed: I read through the wiki on not skimping on underground lines. It seems like the death sentence is moisture on the lines. So I'm digging a grave for my lines to be buried.

Here is the background:
This is fro a Garn install
Running 1" pex lines
Four supply/return runs - so a total of 8 pex lines at 1" each.
Length of the run underground is only about 16-18 feet from the barn to the house.

So now the question: Can I just bury all eight lines together in an uninsulated, heavy-duty, 8" PVC pipe? There will be no seams in the run and all elbows at the end will be glued. I'm planning to bury the line about 24-30" deep in a trench that is about 18" wide. Does it need to be insulated in that short of a run? If so, how would you do it?

I'll run power and data lines separately.

 

[ewdudley]

Advice needed: I read through the wiki on not skimping on underground lines. It seems like the death sentence is moisture on the lines. So I'm digging a grave for my lines to be buried.

Here is the background:
This is fro a Garn install
Running 1" pex lines
Four supply/return runs - so a total of 8 pex lines at 1" each.
Length of the run underground is only about 16-18 feet from the barn to the house.

So now the question: Can I just bury all eight lines together in an uninsulated, heavy-duty, 8" PVC pipe? There will be no seams in the run and all elbows at the end will be glued. I'm planning to bury the line about 24-30" deep in a trench that is about 18" wide. Does it need to be insulated in that short of a run? If so, how would you do it?

I'll run power and data lines separately.

Definitely want plenty of insulation.

For 15 or 20 feet I'd be tempted to construct some sort of dry steam tunnel type of affair and just run 1.5" or 2" black iron. That's a hell of a mess of PEX, the fittings alone would be quite an expense.

 

[sjfrench]

Definitely want plenty of insulation.

For 15 or 20 feet I'd be tempted to construct some sort of dry steam tunnel type of affair and just run 1.5" or 2" black iron. That's a hell of a mess of PEX, the fittings alone would be quite an expense.

That's an interesting thought. Hadn't even crossed my mind. My manifold and all pumps are in the Garn barn. So once I left the manifold, the next step was supply/return to three exchangers and DHW. I'll have to reformat my mind around the thought of running black pipe underground and then splitting off into pex. You just made my brain hurt...and I genuinely appreciate it.

How would you insulate the 8" PVC pipe? Inside the pipe? Outside the pipe? Both?

 

[Nofossil]

I'm assuming that you're using multiple 1" lines to save cost. In any event I'd keep supply and return at least somewhat insulated from each other as well as from the outside.

 

[ewdudley]

... My manifold and all pumps are in the Garn barn. So once I left the manifold, the next step was supply/return to three exchangers and DHW. ...

Oh, I thought the idea was to use four smaller PEX lines instead of one big one because it worked out less expensive for some reason or another.

So assuming you will be running multiple lines from the boiler area, how about piece of 30" poly culvert. Twenty foot section would run something like $550 last time I checked. Cut to fit with a chainsaw, easy peasy. Lay down some foam boards in the bottom and sandwich in the lines. Put a loose plywood floor over it and have a nice storage area with the left over space when you're done.

(For the DHW circuit seems like 1/2" would be plenty to carry enough btus for DHW tank recovery.)

 

[sjfrench]

Oh, I thought the idea was to use four smaller PEX lines instead of one big one because it worked out less expensive for some reason or another.

So assuming you will be running multiple lines from the boiler area, how about piece of 30" poly culvert. Twenty foot section would run something like $550 last time I checked. Lay down some foam boards in the bottom and sandwich in the lines. Put a floor over it and have a nice storage area with the left over space when you're done.

(For the DHW circuit seems like 1/2" would be plenty to carry enough btus to DHW tank recovery.)

I'll have to look into that 30" poly culvert. Not sure I understand what you mean about putting a floor over the area and using it for storage. This run will be outside between the barn and the house. Can you explain that a little further?

Yes, I will be running multiple lines from the barn to the house. These two structures are not attached and about 16-18 feet apart. I'm running a 1" pex for each supply and return. I'm going from the barn to three separate heating zones with exchangers already installed in the plenums (six individual 1" pex lines). I also have a fourth run (2 individual 1" pex lines) to the DHW. I'm actually going to heat two 50-gallon tanks that are side by side. I'll basically go to one tank, run to the second, and then take the return from the second tank back to the Garn. Hope that makes sense. Heating two DHW tanks is part of the reason I was going with a 1" pex.

I am planning on laying foam board under the PVC. I'm not sure that's enough insulation.

Thank you so much for the advice. Please feel free to keep it coming!

 

[heaterman]

Oh, I thought the idea was to use four smaller PEX lines instead of one big one because it worked out less expensive for some reason or another.

So assuming you will be running multiple lines from the boiler area, how about piece of 30" poly culvert. Twenty foot section would run something like $550 last time I checked. Cut to fit with a chainsaw, easy peasy. Lay down some foam boards in the bottom and sandwich in the lines. Put a loose plywood floor over it and have a nice storage area with the left over space when you're done.

(For the DHW circuit seems like 1/2" would be plenty to carry enough btus for DHW tank recovery.)

Saw that done on a farm up north of me. The Garn we installed was almost 300 feet from the house and this guy came up with the equivalent length of 4' diameter steel culvert from somewhere.....I think he's cruising Craigslist when we are all sleeping.....
Anyway, having a hydrahoe on the farm, he dug a trench from the barn mechanical room to house and knocked a hole in his basement wall. You can now walk (hunched over a bit) through the culvert from the barn to the house underground. Being that the culvert was not water tight he "chaired" the tubing up on foam blocks to keep it dry. He used multiple 1" lines for reasons of flow due to the high head.
The culvert makes a nice tornado or bomb shelter...

 

[ewdudley]

Saw that done on a farm up north of me. The Garn we installed was almost 300 feet from the house and this guy came up with the equivalent length of 4' diameter steel culvert from somewhere.....I think he's cruising Craigslist when we are all sleeping.....

I got a kick out of that, it was indeed the inspiration for my suggestion.

I'll have to look into that 30" poly culvert. Not sure I understand what you mean about putting a floor over the area and using it for storage. This run will be outside between the barn and the house. Can you explain that a little further?

I was picturing a 30" hole in the basement wall with all the pipes and insulation laying in bottom foot or so, leaving a foot and a half of space for stashing long and skinny stuff. Like the bomb shelter on a smaller scale.

Yes, I will be running multiple lines from the barn to the house. These two structures are not attached and about 16-18 feet apart. I'm running a 1" pex for each supply and return. I'm going from the barn to three separate heating zones with exchangers already installed in the plenums (six individual 1" pex lines). I also have a fourth run (2 individual 1" pex lines) to the DHW. I'm actually going to heat two 50-gallon tanks that are side by side. I'll basically go to one tank, run to the second, and then take the return from the second tank back to the Garn. Hope that makes sense. Heating two DHW tanks is part of the reason I was going with a 1" pex.

I am planning on laying foam board under the PVC. I'm not sure that's enough insulation.

I was just suggesting using a 30" tube instead of a 8" tube so there would be plenty of bone dry room for insulation and just enough crawl slither space for somebody to lay down the insulation and piping inside the tube. (That is to say, somebody skinnier than me.)

For DHW I was thinking the 1" might be overkill. Running 1/2" at 2 gpm with only 25 degF deltaT would get you 25000 btu per hour, which is roughly equivalent to two 3500 watt water heaters running simultaneously.

 

[Nofossil]

I'd be totally disappointed if you don't install tracks for a garage creeper so that you can scoot through and mess with the minds of houseguests.

 

[Pat53]

When I did my lines I used 1.5" blackpipe. I had about 30' from the boiler to my storage tank in my garage. I dug a trench 3' deep and 2' wide. Had the dude with an on-site spray foam company come out and spray about 6" of foam on all sides of the pipes. Essentially zero heat loss from the boiler to the storage tank. He also put 4" of foam on my storage tank at the same time. Whole deal cost me only $300. Don't scrimp on the underground stuff, you'll regret it sooner or later.

Pat

 

[Tennman]

Boy, that many lines and that short of a distance, a service tunnel would be simple and the ultimate for future maintenance given the number of lines and the short distance. Guard the energy in the system going both ways and don't forget that energy escapes three ways, radiation, conduction, and convection. That basically means to contain the energy the absolute best, it must be trapped at the surface of each pex line. Given you're installing a Garn and most likely you're in this for the long haul with that many lines, I'd do a service tunnel. And, just think how cool that will be at parties when you show off the Garn "reactor" to the guys..."now let me show you the service tunnel to the main facility". Yep, if you go the tunnel route and you crawl thru it and it's comfortable in there, you'll know your insulation needs work.... but you can fix it! I think I'd look at a couple pieces of concrete culvert so I could use the above idea of a creeper in there. Pretty cool opportunity you have there. A Garn and a service tunnel that'd be pretty sweet. Keep us informed, I'm interested how you go.

 

[sjfrench]

Okay...somehow I went from a 24" trench with 8 inch PVC to you all having me build a service tunnel. I'm good for digging a 24" grave to bury the lines...but not a bunker. You all are crazy!

I'll run the lines from the barn, through the ground and come in through a crawlspace. Since my manifold is in the barn, and I have to split from black pipe to pex anyway, figured I might as well do it at the barn manifold.

My main inquiry is if running the lines through heavy duty PVC is a good call. It's only 16 feet from the barn to the house crawlspace. Keep in mind...this is 20 foot section of 8" PVC. Has anyone got experience with running their lines through PVC? How did you, or how would you insulate it?

 

[Tennman]

Yeah... that has a nice ring... service tunnel/bunker... a survivalist's dream. Ok, question 1, should you worry about insulating basically ~100 ft of supply and return pex. I would. I'm not sure how many btus you'll lose, but it will be bad. I think a pro like Heaterman or EW can give you a guess from experience. But this next part is from direct experience. I tried injecting foam into a plastic pipe to encapsulate two 1 1/2" pex lines. An absolute, abysmal failure. I also used sleeves on pex and slid sleeved pex lines into 8" dia plastic ~10-12' plastic to be buried. Even bigger disaster for two reasons, the regular foam sleeves are not great insulators, better than nothing, but not close to polyurethane foam. In my case water got into my plastic tube and at that point it was history (I think you could avoid that with sealed PVC... maybe).

So having been there done that trying to put foam in a tube, that only leaves insulating before you put it in the pex and 4 lines each with a sleeve or a bundle of 4 in one big insulated... something... The best would be 8 thermopex lines.... but for that you'd need a.... bunker. AND do not underestimate in your plan the bend radius you'll need at both ends coming up from the ground whether insulated or just bare. That will be far bigger than an 8" PVC elbow. Gotta go. Gonna be fun hearing suggestions.

 

[Clarkbug]

Okay...somehow I went from a 24" trench with 8 inch PVC to you all having me build a service tunnel. I'm good for digging a 24" grave to bury the lines...but not a bunker. You all are crazy!

I'll run the lines from the barn, through the ground and come in through a crawlspace. Since my manifold is in the barn, and I have to split from black pipe to pex anyway, figured I might as well do it at the barn manifold.

My main inquiry is if running the lines through heavy duty PVC is a good call. It's only 16 feet from the barn to the house crawlspace. Keep in mind...this is 20 foot section of 8" PVC. Has anyone got experience with running their lines through PVC? How did you, or how would you insulate it?

No experience here, but an idea and an opinion. Since its the internet, figured I would let them fly!

I would keep supply and return lines separate to try and avoid loss that way. While your return temps will differ, no sense losing your nice hot supply temp to cold return water. So at the least, two separate pipes.

I would also say dig the trench 30", put in plastic, support two pieces of PVC off of the bottom, then spray foam the PVC. This way the PVC stays warm, and you can put a little great stuff in each end once the apex is in. It lets you replace a line if you have to, and makes sure you don't have a gap in insulation.

 

[brenndatomu]

Yeah... that has a nice ring... service tunnel/bunker... a survivalist's dream. Ok, question 1, should you worry about insulating basically ~100 ft of supply and return pex. I would. I'm not sure how many btus you'll lose, but it will be bad. I think a pro like Heaterman or EW can give you a guess from experience. But this next part is from direct experience. I tried injecting foam into a plastic pipe to encapsulate two 1 1/2" pex lines. An absolute, abysmal failure. I also used sleeves on pex and slid sleeved pex lines into 8" dia plastic ~10-12' plastic to be buried. Even bigger disaster for two reasons, the regular foam sleeves are not great insulators, better than nothing, but not close to polyurethane foam. In my case water got into my plastic tube and at that point it was history (I think you could avoid that with sealed PVC... maybe).

So having been there done that trying to put foam in a tube, that only leaves insulating before you put it in the pex and 4 lines each with a sleeve or a bundle of 4 in one big insulated... something... The best would be 8 thermopex lines.... but for that you'd need a.... bunker. AND do not underestimate in your plan the bend radius you'll need at both ends coming up from the ground whether insulated or just bare. That will be far bigger than an 8" PVC elbow. Gotta go. Gonna be fun hearing suggestions.

Could use a 8" PVC conduit sweep ell, maybe 36-48"?