Stationary Compressor Mounting Pads?

[Bird]

Gary, I used the PVC air lines for a few years myself with no problem. Like you said, they were inside the shop out of the weather, although it was an uninsulated, unheated metal sided building. And I, too, have seen a PVC water line with a small crack leaking on one of my outside hydrants. However, a fellow who worked for me had a little mobile home at the lake and he once forgot to turn the water off before a freeze and he said that PVC shattered and he had to completely replumb the trailer.

 

[VA_Joe]

I don't know what the right answer is. I was using some 3/4 inch PVC pipe last weekend and it said in big red letters "not for compressed gas". Since water pressure can be as high as 70 or 75 psi (that's what my relief valve is designed for) my guess is that 125 psi is within the margin of safety. Does anyone know what PVC (with cement joints) is actually designed for (I don't remember seeing any indication on the pipe).

Joe

 

[JustGary]

You can buy PVC pipe in different pressure ratings, which should be stamped on the outside of the pipe. The pipe does derate as it gets colder, but the chance of me actually using it when it is really cold is pretty slim. The pipe is rated at 73*F, and it's barely below that here in NW FL in the middle of November. For those of you who live north of I-10, I can't say what might happen if you use PVC for air pipe.

In my case, if it cracks or splits or blows out I'll probably just put a new stick in its place for about $3.

Oops, to answer the question, I noticed at This here page that 200 PSI pipe is cheaper than Schedule 40 pipe. The 1/2" Schedule 40 is 600 PSI at 73*F. 3/4 Schedule 40 would be close to that.

- Just Gary

 

[VA_Joe]

Interesting page. Thanks.

 

[Gravy]

Do NOT use PVC for compressed air. I have personal experience with schedule 40 pvc pipe shattering and putting plastic shrapnel through 1/2" sheetrock. If a person had been nearby, it could have been really ugly.

There are plenty of alternatives - iron and copper pipe, the GaragePak approach if you've got the $$$, various hoses and tubing that are designed for compressed air. Using PVC doesn't save enough money to be worth the risks.

Gravy

 

[CT_Tree_Guy]

I agree with Gravy 110%.

Using PVC pipe for this application violates my #1 safety rule - I call it the "little bell" rule. If a little bell goes off in your head when you're about to do something saying "well, I know this isn't quite right/safe/recommended/according to the book ... but I'm going to do it anyway" .... stop, and don't. (Or at least try VERY hard not to. We've all had to "push the envelope" when the heat is on, but I don't see this as that type of situation. And I also don't really see this as a "little bell" going off - more like a two-man gong).

Call me an old lady (You're an old lady!) but there's so much that can go wrong when you DO things "by the book" that there's no point in tempting fate with the laws of physics. There's a good reason that the PVC pipe is labelled "not for use with pressurized gas".

Think of that pressurized PVC as a bomb waiting to go off. Maybe not all by itself (or maybe so), but have you ever had something big and heavy smack into something else and break it? I have.

And while the pieces of (potentially) flying PVC might be light, I wouldn't want one stuck in my eyeball.

Plus, black pipe better helps to keep moisture out of your system by condensing water vapor and allowing it to run down into the drop legs (with valves on them for expelling water) that are part of a well-designed system. Some people like copper for its corrosion-resistance. I'm a black pipe guy for its toughness and threaded joints, but I'd consider copper for future installs.

Please forgive me if I'm coming off a little strong here, I'm just trying to keep everyone as safe as possible.

 

[VA_Joe]

I guess I shouldn't use it for hydraulic lines either. /forums/images/graemlins/grin.gif

 

[Farwell]

I agree with you 100%.
Farwell

 

[CT_Tree_Guy]

Joe -

Well it just says "pressurized gas", so you should be good to go /forums/images/graemlins/laugh.gif

 

[mark777]

RichT,

I used pvc for years and never had a problem. Then one day while visiting a local discount tire shop, there was an incident with a section of 1" pvc plumbed to their tire machines (about 10 years ago). The flexible airlines from the pvc to the machine were fine, but the pvc lines secured to the wall (one in particular) blew apart. At the 'T' fitting, where the run included a water drain, it quite literally exploded, sending pieces flying across the shop at quite a high velocity.

The employee told me that it was the second time it happened in the 5 years he worked there. He also stated that the slow build up of pressure and then the immediate drop from using high CFM equipment causes the pipe to surge and weakens the joints.

That incident was enough for me. I will never use pvc in combination with air again.

At my latest shop I built a few years ago, the building inspector (my machine room) came and inspected for PVC. Here in this county, it is a "Red Tag" special. Even though all of my airline in the shop is 3/4" copper, he still checked the compressors at the source to make sure there were no pvc attachments plumbed anywhere.

The inspector said that in any commercial or residential application, PVC is not to code in conjunction with compressed air, any and all platic plumbed pipe must be removed.

Just my heads up as I don't know what your county state codes are.

Regards, Mark