PEX pipe diameter

[Jerry.Tan]

I worked as a plumber in the 80's, and back then, plumbing was mostly copper or the older galvanized steel. PVC was being used for drainage, and CPVC was available but not legal in some places. PEX did not exist yet, (as far as I know), but was not sold for common household use.

Anyhow, I want to replace the pipes in my own house, which are copper, but were installed poorly and regularly freeze in winter. While considering moving some of that copper pipe, and sticking with copper, I found that copper pipe is much more costly than it used to be. I decided to look into PEX. I have heard the pipe is strong, does not break easily if it does freeze, and fairly easy to install, once the expensive crimping tool is purchased. At the same time, the brass fittings are very expensive, and while the PEX itself appears to hold up well if it freezes, I question how well those brass fittings hold up if they freeze.

I was almost sold on the PEX, despite paying the high price for the fittings and having to by that costly tool, until I noticed the ID of those pipes. A so called 1/2" PEX is really only about 3/8", with the fittings being close to 1/4". That may work fine for a bathroom sink, but I question how slow the shower will run, and know that an outdoor spigot for the garden hose is going to have poor flow. Using 3/4" for everything is more like using 1/2" copper, so I'd almost have to use 1" pipe to feed the outdoor spigot.

I can now see why they use a manifold system when they install PEX, because daisy chaining from fixture to fixture will result in poor flow and pressure.

My house has no basement, so I have to install the pipes inside walls, or on top of the interior walls and hide them with trim, to avoid ripping the whole house apart. Thus, the manifold method is not appropriate because it would require too many pipes to hide.

I've decided to go back to using copper, or maybe use CPVC, which I know is easy to install, but I know it dont hold up well if it freezes.

At the same time, I question how the PEX industry can legally call their pipe 1/2" or 3/4" and so on..... when it's really one size smaller than it's rated. To me, that is false advertising.

[philoÂÂ]

Not exactly answering your question but I am a non-plumber and I recently replaced some very old pipes.

I used Sharkbite no expensive fittings and no tools needed.

In all the years I've (as an amateur) done plumbing repairs, it was the first time there were no leaks , the very first time.

[Ed Pawlowski]

It is called that since the OD is the same and can use the same fittings, such as Sharkbite and replaces the copper of the same nominal size.

You state is it one size smaller than rated. What is it rated? Do you have numbers? I have to assume you looked up the flow ratings and have the figures. Maybe you can bring a class action suit and have lawyers make millions of dollars.

I have some PEX in my house and do not notice any flow restrictions and yes, if feeds my showers both hot and cold. I also have a section of 3/4" PEX replacing a section of copper in my baseboard heat. Saved a lot of headaches I had with the copper in that section over the years.

You may find this of interest The terms PEX pipe and PEX tube have been used interchangeably, however some manufacturers distinguish between the two by manufacturing to different inside/outside diameters. For example, PEX pipe may be manufactured to IPS-ID (iron pipe size, inside diameter controlled) sizes with varying thickness to meet pressure requirements, while PEX tube may be manufactured to CTS-OD (copper tubing size, outside diameter controlled) sizes, commonly with a standard thickness of SDR-9 (standard dimension ratio).

Here are actual sizes Note that 1/2" is .475 ID

It is larger than what you state as the size smaller in copper. 3/8 copper is .402 in K, .430 in L .450 in M so PEX is in between.

[Jerry.Tan]

Sharkbite fittings are very expensive. Sure no crimp tool is needed, but those fittings are around $7 and up. That's no biggie for a repair needing 2 or 3 fittings, but to do a whole house will need at least 30 fittings. And if I used all 1" and 3/4" PEX, the fittings are more costly. So, just the Sharkbite fittings alone would be at least $300.

I figured out I can plumb the whole house with CPVC for around $100. (pipes - fittings - glue/cleaner - and hangers). Does not include sink faucets, valves, shower control, water heater, etc. Most of that stuff I'll reuse what's here now. I'm just trying to get rid of the copper pipes that are almost all under the crawl space or on exterior walls, and tends to freeze every winter, which not only is aggravating, but does further damage when it thaws and soaks stuff. I'd rather see the pipes inside the house than deal with the freezing issues.

Smaller than the measurements given, such as 1/2" No, I did not look up flow ratings. It's very obvious just comparing the stuff in the store, that the PEX ID is not even close to rigid copper or steel.

No lawsuits. Not worth my time. I just wont use it.

I was not aware of the two types. Th stuff sold in the stores, all has smaller ID than comparable Iron or copper or even the CPVC.

Yes, the pipe is not as small as I said, but the fittings are. The flow of any pipe is the diameter of the smallest pieces. Pretty much the same as a chain is only as strong as it's weakest link. The ID of the fittings is about the same as the supply tubes under sinks. That's why the PEX would be fine for sinks, but not for showers, and particularly not for an outdoor spigot. Plus diasy chaining them would make the flow worse. Most home (supply) plumbing beginning with steel pipe, (and the really old lead pipe), used 3/4" and went down to 1/2" as the daisy chaining ended. To be somewhat comparable using PEX, one would need 1" and taper down to 3/4" at the end of daisy chains.

The OD of a pipe dont mean shit, it's the ID that determines flow. I do understand that the walls need to be thicker compared to metal pipes, but it should not be called 1/2" when it's not even close. In the store, I took a piece of rigid copper 1/2" and a roll of 3/4" PEX. The ID was about the same. (Of course I'm comparing 1/2" to 3/4"), but the ID of the 1/2" PEX was considerably less.

I'll have to admit that this is not the first time plumbing has not lived up to it's "rated size". flexible copper (in rolls) has always been rated different than it's actual size. That's why a lawsuit would not make sense. In many ways, it's a shame they never came up with more sensible standards.

[bob haller]

CPVC is cheaper but freezes and breaks easily. Plus its 10 foot lengths.

You will be spending lots more time in the crawlspace:(

Check around for sharkbite costs, Home depot many are 5 bucks each, and less on line.

I did my very first pex job last winter ZERO leaks and really easy:)