PVC for OWB installation

[rmagill]

Hi, I am new to the site and an just starting my install. I have been reading alot and I had a question.
I see many installations with pex and copper. Once the insulated pex comes in the house can you use PVC instead of pex or copper.
My reason for considering it is that pvc is so much cheaper and easier to work with.
Another question is.. How deep do you really have to dig when using ThermoPex? I have a short 35' run. I am down about a 12" and am now hitting some serious rocks.
Thanks

 

[STEVEGODSEYJR]

I think the best thing to do is not go cheap. Yeah... you save a little money here and there but it bites you in the arss in the end. I cheaped out with the insulation around my underground lines and I have a long wide strip in my yard when it snows. I should have just bought some logistor or something similar. Best way is do it right the first time. Steve

 

[blackdogon57]

PVC wll not stand the heat - even Schedule 80 is good for only 140F. Pex is cheap and easy to work with - give it a try

 

[smokinj]

PVC wll not stand the heat - even Schedule 80 is good for only 140F. Pex is cheap and easy to work with - give it a try

+1 pex is good to 180

 

[rmagill]

Thanks for the quick answers. How about the trench with the Thermo-pex, How deep do you really have to go?

 

[mtfallsmikey]

I think the best thing to do is not go cheap. Yeah... you save a little money here and there but it bites you in the arss in the end. I cheaped out with the insulation around my underground lines and I have a long wide strip in my yard when it snows. I should have just bought some logistor or something similar. Best way is do it right the first time. Steve

DITTO!...PVC no good....bury the lines to at least the average frost depth in your area, mine are 40" deep....see disclaimer below...

 

[Labman]

CPVC is just as easy to work with, takes the heat better, and only costs slightly more than PVC,

 

[MS-310]

Do not use PVC or CPVC it wont last at that heat. I do know for a fact I seen CPVC used and lasted for about 2.5 years then it failed. PEX pipe is about less then $.85 a foot use it and dont be worried. For the underground pipe keep it below the frost line.....Just a good rule of thumb.

 

[kalib stock]

Do not use PVC or CPVC it wont last at that heat. I do know for a fact I seen CPVC used and lasted for about 2.5 years then it failed. PEX pipe is about less then $.85 a foot use it and dont be worried. For the underground pipe keep it below the frost line.....Just a good rule of thumb.

:agree2:

 

[oneoldbanjo]

I thought the reason you don't use PVC is that it will allow Oxygen to permeat and reach the water - and the PEX will not. The water in the system is not supposed to have any oxygen in it or it will rust the boiler. The PEX will not allow the oxygen to pass through the pipe to supply oxygen to the water.

 

[mtfallsmikey]

I thought the reason you don't use PVC is that it will allow Oxygen to permeat and reach the water - and the PEX will not. The water in the system is not supposed to have any oxygen in it or it will rust the boiler. The PEX will not allow the oxygen to pass through the pipe to supply oxygen to the water.

Not all PEX has an oxygen barrier...and it is not needed on open systems, like typical OWB systems.

I'd just rather not use CPVC for heating apps...even tho it's rated for 200 deg., some fittings are not hot-water rated.

 

[smokinj]

I thought the reason you don't use PVC is that it will allow Oxygen to permeat and reach the water - and the PEX will not. The water in the system is not supposed to have any oxygen in it or it will rust the boiler. The PEX will not allow the oxygen to pass through the pipe to supply oxygen to the water.

that two!

 

[trialanderror]

+1 pex is good to 180

spec sheet on the logstor i bought is good to 203F.

 

[trialanderror]

I thought the reason you don't use PVC is that it will allow Oxygen to permeat and reach the water - and the PEX will not. The water in the system is not supposed to have any oxygen in it or it will rust the boiler. The PEX will not allow the oxygen to pass through the pipe to supply oxygen to the water.

that's a good theory too, but most 'outdoor wood burners' are open loops to the atmosphere, unlike the traditional boiler. Boilers operate up to 30PSI, so you can achieve 260F+ temps without boiling....

i used 2" steel pipe for my garage setup, i kept the water at 210F and open to the atmosphere, just tested the water occasionally to keep it neutral and nothing was severely rusted. surface rust is normal, big handfuls of boogers and globs floating around is another story.

but everyone favors OWB's instead of boilers because of laws and code being the pressure they operate.....everything inside the house is like a big bomb waiting to fail....

 

[Lurch16th]

Glad I saw this 2 mins before i was on my way out to buy a bunch of cpvc 6" an under, to make a heat exchanger for my pool. Back to square one, with stainless steel i guess.

 

[ghitch75]

i got cpvc run to my water/air and to my water heater for almost 5 years now and it looks as good as the day i did it.....just use FLOWGUARD GOLD brand and brass insert adapters and it will last for years....here is a pic of my water heater...

 

[blackdogon57]

pvc =

a big bomb waiting to fail....

 

[AIM]

I have no educated answer of my own but a local dealer/installer of OWB's only puts his lines down 18" or so at the MOST. As a matter of fact. He told me to trench to 18" and put a few inches of stone in PRIOR to laying the pipe. He says to keep them high to avoid as much ground water as possible. (he is using the foamed in 4" corro pipe) Many times here I have read where guys just laid their lines out on top of the ground for the first year due to a late install and had no problems so I see no real point in keeping them below the frost line.

As for CPVC once you hit the house. All I can say is that my garage has been this way for 2 years now without a problem. 2 years isn't much of a test though. Now that I am better set up to run pex I'd likely just do the whole thing with pex though.

 

[Lurch16th]

Well in theory, if the owb is never shut down, the lines will never freeze anyway. But, 40" of ground is a better insulator then 18". So it may just be a trade off of personal preference.

As for the cpvc, it's hazy, but coming back to me now. I had a rental unit for about 16 years. Most of the plumbing was cpvc and was nothing but a pain in the A$$. I remember fixing many a leak and the thing that was most irritating was you have to let the glue cure for 8 - 24 hrs. So I always had to come back and tenants were without water. Any chance i had, i replaced a run with copper.

But that's under street pressure, 50 - 100 psi. My OWB runs maybe 3 psi.
Still, I'm staying away from cpvc.