insulating OWB lines

[sw18x]

I bought a house with an OWB three years ago and I'm losing almost 15 degrees of heat between the furnace and the house. The lines leave the house and the OWB in pvc pipe, the install was about 12 years ago and so I have to assume they didn't insulate the lines. My summer project is to dig them up and insulate them. Given the fact that 15 x 2 = 30 degrees of heat is lost to the ground every time the water leaves the OWB and returns, I'm looking forward to saving some wood and getting my gas bills down to 30 bucks a month (right now a gas boiler supplements the OWB).

I'd like to hear some thoughts on my current plan. Rather than replace all the lines, what I want to do is expose the old pvc, then slide larger sections of tongue and groove pvc pipe over the top of the old pvc. These new sections will be 5 or 6" diameter, with 2 or 3 pre-drilled holes in each section large enough to fit a spray foam nozzle. I'll center the new sections of pvc on the old, then fill them with spray foam, so the old pvc containing the pex lines will be completely encased in spray foam.

I haven't priced out the tongue and groove pvc, but I'm assuming they will be cheaper than buying the same length of insulated pex tubing. It will be a painstaking process digging alongside and under the old pvc once we expose it with the excavator, but if my labor saves me money then so be it - I've got a 16 year old nephew on summer vacation and the way I see things, it will be good for his work ethic.

Any thoughts on this would be much appreciated.

 

[brenndatomu]

How long of a run we talkin? If it's not too long I'd dig it up and replace it. I bet your lines are insulated, just waterlogged. Also, I don't think your plan will give you thick enough insulation to make any real difference for all your trouble. It may be a lot less trouble/better results in the long run to just dig and replace, and, there are some really good preinsulated lines out there now.
My dad had this same issue, so they had to dig a sump at one end to install a sump pump with a float to dewater the ditchline. It made a big difference, but I'm sure their insulation is still wet and they are still losing more heat than they would be otherwise. They were gonna put in new lines with closed cell insulation inside 6" SDR35 PVC sewer pipe (watertight), but at over $12k for the materials (due to the length/multiple runs) they decided the heck with it, it's good enough for now.

BTW, what the heck is tongue and groove pvc pipe???

 

[sw18x]

Based on some other problems we saw with the original setup, my money is still on finding no insulation once we dig.

Question: if you run insulated lines through sealed pvc pipe, wouldn't that prevent waterlogging?

Here's an example of tongue and groove pvc. With 6" pvc encasing 3" pvc, that would give me 1.5" of spray foam. I'll have to ask my spray foam guy what kind of insulating properties that would give me.

Tonue & Groove Split PVC Pipe - Osburn Associates, Inc. Store

 

[sw18x]

ok, scrap that plan - the current pvc is 4", shrouded by 6" pvc that would barely give me 3/4" of insulation.

Looks like I'll probably tear the whole thing out and go with insulated pex. I've got about a 60 foot run, I'm only insulating the boiler lines (the domestic hot water lines do just fine right now, I don't see the need for the extra expense to get our water hotter than we need it), so that would be 120 feet. I found a 100 foot roll online for $264, my buddy is a plumber so I'm hoping he can get me a good price and can scrounge up the extra 20 foot.

So this brings us to a new round of questions:

What's the best way to go about this? Simply seal the insulated pex in pvc? I'm still tempted to fill the pvc with spray foam, or even double shroud with two layers of pvc and fill the second larger OD pvc with spray foam, since some of the pex lines will be in direct contact with the pvc. This will also safeguard against waterlogging. Let me know what you all think.

 

[NSMaple1]

Forget all about putting lines inside other pipe.

Excavate the whole thing, get rid of all PVC pipe and everything else in the trench besides just the water lines, and hire a spray foamer to spray foam the lines with closed cell foam right in the trench. Space the pipes apart from each other a few inches, and get a good 6 inches or so between the pipes & dirt all around.

 

[sw18x]

I've heard of other guys doing that, my concern is: won't the spray foam break down over time if you just pile dirt over it and leave it exposed? Definitely sounds like the easiest way to go though.

 

[sw18x]

Also, can you get away with non-insulated (cheaper) pex if you have 6" spray foam insulation?

 

[NSMaple1]

Hint: google 'underground lines not the place to skimp'

 

[RiverRocket]

ThermoPEX® - Insulated Piping
This is the only way to go...JMO

 

[blackdogon57]

ThermoPEX® - Insulated Piping
This is the only way to go...JMO

I wouldn't even dig the old stuff up.
Trench next to it. Bury thermopex and be done in a few hours.

 

[Johnny Yooper]

Thermopex, period. I have 140' of it going in next weekend, replacing 4 inch insulated PVC pipe I put in 9 years ago; a long story for another day. After significant research over the last year, I opted to go with Thermopex (I have poor draining soil with high water table especially in the spring.....you can guess my story already). It's not the cheapest method out there, but as the saying goes, you get what you pay for.

 

[xrayman]

go with thermopex. I had mine laying on the ground the first winter I had my c.b. it had a foot of snow on it a week after i layed it and never melted the snow.

 

[AIM]

Just read the MANY MANY MANY threads about failed do it yourself insulation. Then go buy the thermopex.

 

[sw18x]

Thanks for the replies. I like the look of the thermopex, but I'm afraid to ask what it costs per foot. I'll give them a call today and get a quote.

According to their website, thermopex comes in 1" and 1 1/4". My lines measure 7/8" on a tape measure, do I have 3/4" lines or 1"?

If my current lines are 3/4" and I go with 1", what kind of effect will it have on my pump circulation? Anything to worry about?

And you're right, doesn't even make sense to dig up the old lines, just trench alongside it. The picture of the install on the thermopex website looks like they barely even cover the lines, how shallow can you get away with when using the thermopex?

Thanks again!

 

[upsnake]

When I put mine in it was in the 12 dollar a foot range.

CB has some pretty good info on installing the line on their site. I think it is like 12 -24 inches. Mine are right around 18. I also have poor draining, high water table soil. (had to keep pushing my pipe down when installing it b/c it was floating in water). I have had no problems with so far been in 3 years.

Oh ya i have 1 inch pex lines too, not sure on the actual ID though.

 

[blackdogon57]

My 1" pex is 1" outside diameter and uses 3/4 fittings for valves/corners etc. Pretty sure the thermopex is the same when you cut back to make connections.

 

[hanniedog]

Read where you had some stuff lined up but was 20 ft short. Just my two cents don't end up with an under ground connection if it can be avoided.

 

[RiverRocket]

You'll be fine using 1" Thermopex.
I've heard of people burying it just deep enough to get a couple inches of dirt over over it...to people burying it 4/ft
I think the depth depends more on what kind of traffic your gonna run over it..if it's just lawn mowers and foot traffic go shallow, if your going under a driveway go deep...

 

[RiverRocket]

Read where you had some stuff lined up but was 20 ft short. Just my two cents don't end up with an under ground connection if it can be avoided.

They make a water tight splice kit that does a really nice job...

 

[jh35]

My neighbor has 150' run and loses less than 2 degrees with Thermopex. I have a 90' run of Thermopex but haven't checked the loss. I paid $11/ft last fall.
Another neighbor has done it the cheap way three times which adds up to way more than doing it right one time.

Jeff