Gray vs White PVC

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Barbqranch

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Arcata, CA
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Plant maintenance electrician Semi-retired
My understanding of why you should never use pvc for compressed air is that failures are catastrophic. Water compresses very little, so if the pipe cracks, the pressure goes down quickly as it leaks out. Compressed air, on the other hand, will keep pushing on the pipe longer, causing it to sometimes explode.
 

GoldDigger

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Placerville, CA, USA
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Retired PV System Designer
My understanding of why you should never use pvc for compressed air is that failures are catastrophic. Water compresses very little, so if the pipe cracks, the pressure goes down quickly as it leaks out. Compressed air, on the other hand, will keep pushing on the pipe longer, causing it to sometimes explode.
My comment was not on using PVC for compressed air but rather pressure testing a pipe system before putting it into service.
It is true that there would be a greater risk in the event of a pipe failure, but that would have nothing to do with the instructions on the glue itself.

PS: I am currently fighting an underground outdoor irrigation water system in which it seems that every 10th joint or so was incompetently glued. Each new stress opens another joint....
 

FionaZuppa

Senior Member
Location
AZ
Have you considered using sprinkler pipe?
i have not. irrigation poly is only rated for about 80psi, and in normal use the pressure in the poly will be less than line pressure because when poly is "on" the water is leaking out from many places. irrigation poly has on/off valve on the upstream side, thus when "off" there is no psi in the pipe, etc. and, fittings are dismal.

there is NSF poly pipe, rated at 200psi, but its like $2/ft !! NSF 100psi is 32c/ft. white PVC is ~20c/ft

but hey, PEX seems to be about on par with white PVC, and it comes in long rolls. i do however need to make a few connections, so i have to weigh the cost of tools too.
 
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iwire

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Location
Massachusetts
is this info correct

"PVC is fine to use outdoors. The pressure is also fine. Schedule 40 is good for a working pressure of 200 psi+ all the way to 1-1/2" size.
It's mandated by ASTM D1785. All PVC must meet this code.
"

PVC conduit is not pipe, it is conduit and I highly doubt it is tested or designed under a pipe standard
 

FionaZuppa

Senior Member
Location
AZ
ah, pex is the way. only ~18c/ft + a few fittings. i'll use sch80 for the risers (hose spigot, etc).
any of the metal fittings will get some yellow snot and a tape wrap, should be good until i am gone to the after-life, etc.
 

FionaZuppa

Senior Member
Location
AZ
If you use PEX, check sizing to make sure you get the flow you need. I believe the ID of PEX is smaller than other pipe material.

yeah, agreed. its just some outdoor water for garden hose. my 18c/ft is way off, the guy on the phone did not clarify. its actually 50c/ft for 3/4" pex.
sched40 white 3/4" pvc with bell end is just 24c/ft. 3/4" electrical sched40 bell end is 20c/ft. using electrical conduit i can save $12. but, i have no definitive info on if it really matters if i use the gray stuff....... so i'll just spend the extra $12.

the pex price was local retail, online a 300ft roll is just 24c/ft, but it will take days for me to get.

thanks for all the feedback.
 
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GoldDigger

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Location
Placerville, CA, USA
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Retired PV System Designer
... to be about on par with white PVC, and it comes in long rolls. i do however need to make a few connections, so i have to weigh the cost of tools too.
I am working on a DIY project which uses PEX for hot and cold. I used 3/4 PEX from hot water heater to manifold and homerun 1/2" everywhere else from there. Seems to be working OK. On the cold side, 1" PVC to a manifold connected with 3/4" PEX and 1/2" PEX to everything but the water heater inlet (that is a pass through 3/4" from the manifold.)

I chose the copper crimp collars and crimp die that uses Channellock pliers instead of the more expensive re-usable spring clips and expensive crimp tool. No regrets so far BUT be sure to follow the recommended 1/8" or 1/4" spacing from end of PEX to crimp collar or you will get leaks. BTDT, got wet T shirt.
 

FionaZuppa

Senior Member
Location
AZ
I am working on a DIY project which uses PEX for hot and cold. I used 3/4 PEX from hot water heater to manifold and homerun 1/2" everywhere else from there. Seems to be working OK. On the cold side, 1" PVC to a manifold connected with 3/4" PEX and 1/2" PEX to everything but the water heater inlet (that is a pass through 3/4" from the manifold.)

I chose the copper crimp collars and crimp die that uses Channellock pliers instead of the more expensive re-usable spring clips and expensive crimp tool. No regrets so far BUT be sure to follow the recommended 1/8" or 1/4" spacing from end of PEX to crimp collar or you will get leaks. BTDT, got wet T shirt.
as i have found, PEX pricing is more than std sch40 white bell end PVC pipe.
 
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