Why are pipes used in plumbing more than hoses?

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I thought PEX was just an industry term for HDPE pipes, but no, you're right. The X stands for crosslinked and irradiation is one of (the more expensive) ways of achieving it. It sounds like most common PEX is made by adding peroxides to the HDPE or LDPE before extrusion and the chemical causes the thermoplastic to become a thermoset after the heat and pressure of the extruder. Neat stuff.

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Ah! I was wondering how such a seemingly simple hose had a corner on the market. Apparently it's not a simple hose at all!

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It sounds like you may know. Does PEX have all those same concerns about plastic water bottles, the BPA and people say there are many more chemicals that didn't get the same attention.

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Plumbing Apprentice here. Garden hoses wear out in 5-10 years, and ideally the water and drainage pipes will be there for decades.

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Do they wear out because they’re exposed to the elements and movement, or because of their material? I read that as “what if you were to put a hose in the wall?” Would its rate of degradation be the same as say a pvc pipe?

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- Over time the rubber of the hose dries and cracks, and the elements/movement can expidite that process. I guess a hose inside of a wall could last much longer depending on the material. If they were made in the same way Fernco fittings are made, they could last a just as long (Fernco claim the fittings can last 50 years, but the company has only been around for ~50 years so the claim can't really be tested).
  
  Pvc is designed to last 50 years but some people claim that its useful lifespan is 75-100 years, but Pvc hasn't been around long enough to test the 100 year claim.
  
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Huge disclaimer that I'm not a plumber or even close to a plumber, but I did have a house and think about houses:

Isn't the current "standard" plumbing PEX plumbing, which is basically just a bunch of hoses?

Like I think you're on to something but the industry beat you to the punch 😉

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Even now in some places repairs are done with cpvc. Op may be wondering why they didn’t choose hoses in the first place.

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- Oh, good point! Yeah, in our old house (copper plumbing) plumbers usually did repairs with cpvc, not sure why.
  
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I recently had to have my 1980s house's water main connection replaced because they used some experimental flexible hose material from the late 80s and it's all starting to embrittle and fail now. Wouldn't have happened with PEX...

I've been reading about PEX now and it sounds like it only became commercially viable to produce in large volumes in the 1990s, even thought it's existed as a form of polyethylene since the 1930s. It's just now becoming cheap enough to be used everywhere because it's obviously better and we have lots of material performance data on it.

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- Polybutylene. Yeah bad times if you’ve plumbing made out of it the US.
  
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- some experimental flexible hose material from the late 80s
  
  I got you beat there. My house had cardboard sewer pipe. Orangburg pipe.
  
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@ALostInquirer As others have pointed out it is largely a matter of price and durability. My background is in industrial equipment so keep that in mind. It is worth noting what differentiates pipe from hosing at least in my industry, pipe is a tube made of a single solid material of a certain thickness, tubing is a single material tube of a thinner wall thickness, and hose typically consists of multiple layers or materials to maintain flexibility while still being durable. Some industries like medical may call a flexible tube of a single material a hose, but this is usually colloquial and not the official terminology found in standards and regulation.

Because hoses are made of multiple materials and typically laminated or woven and adhered together they are much more complex to manufacture, and so more expensive, often at minimum 5x as expensive. When you look at hoses meant to last for decades this can go up a lot, 10-20x, this is because flexible materials in general degrade over time and become brittle and/or porous, prone to springing a leak. The methods used to prevent this require expensive chemicals, or patented processes which keep prices high.

PEX is growing in popularity because it is flexible and durable but relatively inexpensive, only 1.5-3x as expensive in cost of materials as CPVC typically. PEX is a type of pipe/tubing made of Cross-linked Polyethylene, which is a singly polymer, Polyethylene, that has been either treated with a chemical such as a peroxide or silane, or irradiated with an electron beam, to induce cross-linking of the long-chain polymers. This Cross-linking makes the material much more durable and elastic, while requiring only a single treatment and no lamination or weaving. As such PEX can be manufactured more cost effectively than hose, making it a good middle ground between rigid pipe like cPVC or copper for potable water applications.

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Thanks for the detailed reply! My suspicions were that it may have been related to the complexity of manufacturing (including the materials development that's enabled it within the past several decades), but the costs alongside that had slipped my mind given the scientific reasons that would have been more of a hard block in the past.

Also across the various replies here, TIL a bunch more about what's up with PEX, which I'd not gotten around to researching. Sounds like some wicked stuff all things considering!

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- @ALostInquirer Yes, Pex is pretty good for a lot of things, though it does have it's weaknesses. For instance it is UV sensative and will break down and crack of left in the sun. Also, the fact that it is often joined with compression fittings like the proprietary Sharkbite connectors does make assembly faster, but the failure rate of those components is higher than an adhesive bonded sleeve fitment. Being flexible also has its downside, for while it is nice to be able to bend the pipe to conform to angles, you do have to bend it to each and every stud penetration individually rather than being able to thread a hard pipe through all in one motion.
  
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Isn't a pipe just a stronger hose?

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Pass me that blunt

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I work in construction and will give you the common viewpoint (non-US).

We use PVC pipes to drain used water and PPRC pipes to supply fresh water to flats in an apartment. These are all installed to be practically permanent. The concrete is put in place on top of these pipes.

I imagine hoses can be used for the same purpose, but the price would be simply higher and no investor would prefer hoses over pipes for this reason. If there is a type of hose that is as effective as these pipes and as affordable, it's not available in my region

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After doing plumbing professionally for 10 years I've come to the conclusion that the main reason is difficulty of insulating PEX once it's installed. Plumbers don't generally do insulating in commercial jobs. There's inherently no such differences in quality that would make PEX unsuitable for most applications. Still we seem to prefer either composite pipe for water or steel for heating. PEX mainly when it's installed somewhere you can't check for leaks later bexause with PEX you can do it with minimal to no joints. Underfloor heating for example.

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The standard PEX is somewhere in the middle- a stiff hose.

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While I’m not a plumber there is something to consider as well.

Water hammering

I think this is why something like Pex works well since it’s flexible while not being so flexible that you’d have to worry about long term abrasion and wearing away from a hose bouncing back and forth from it.

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But water hammer is an understood, fixable problem. It’s mostly that modern appliances have solenoid valves that switch too quickly for older piping found main most peoples homes. Even then, a water hammer arrestor will usually cover it

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Pex is also resistant to bursting in the event of freezing. I used pex in my van build and the few times the pipes have frozen haven't resulted in any issues other than having to wait for the pipes to thaw.

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I would call most plumbing as hoses as they are using flexible plastics in most installations. Pipes are generally referred to as rigid items. But that is selective even. Hoses under some definitions are pipes with multiple layers. Ie. Rubber and a metal mesh grid for strength.

Think the definitions are quite interchangeable. We simply use the cheapest most dependable option available that adheres to code.

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Hoses are much more useful if they can bend and be coiled up. Pipes usually are quite hard to bend.

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