# pex vs. copper for an indoor boiler



## tjvt (May 29, 2014)

Aside from pex being a whole lot cheaper, any other advantages to pex vs. copper?


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## JMac23 (May 29, 2014)

We'll if you don't care how it looks at all, it's a lot easier to get it where you need it. Keep in mind the fittings are much more expensive, & unless you are borrowing the tool that will be pricey too!


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## goosegunner (May 29, 2014)

How about any overheat situation?

Pex surely will not handle the same heat and pressure of copper or iron pipe.

gg


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## Clarkbug (May 29, 2014)

Pex expands a LOT more than copper or black iron.  Just keep it in mind, not necessarily a good or bad thing.


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## maple1 (May 29, 2014)

I don't think I've read of any copper failures. I have read of pex failures.


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## bmblank (May 29, 2014)

If frozen copper will bust open. Pex usually doesn't.


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## mike van (May 30, 2014)

I ran copper, 220 ft of 1 1/4"    It stays nice where you put it, without the movement of pex.  If I have to, I can sweat a fitting without running out to rent a pex tool.   Copper is a one time investment.


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## velvetfoot (May 30, 2014)

mike van said:


> I ran copper, 220 ft of 1 1/4"    It stays nice where you put it, without the movement of pex.  If I have to, I can sweat a fitting without running out to rent a pex tool.   Copper is a one time investment.


Have people here used an equivalent amout of pex?  That's a big investment in copper.  As an aside, I just did my first pex plumbing job in the house, and it's very easy to do the joints.


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## maple1 (May 30, 2014)

bmblank said:


> If frozen copper will bust open. Pex usually doesn't.


 
Yes, true. But in an indoor boiler situation, I think I would be hesitant to use pex. A sudden burst of 200+° water could do some serious damage if someone was in range. Boilers can easily go over 220° in an overheat situation. I would stick with copper or black iron.


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## foamit up (May 30, 2014)

All my boilers have 1 1/4" pex in the long runs, once i got to the last 12 ft before the boiler i switch to black iron pipe. I just have a couple 90's before or after the pex joint to take up expansion. I have not notice any expansion in my systems and have not had any burst or broken pipes. Before crimp rings were so handy to get for this size i used double hose clamps on every joint with barb fitting. They are still working. So get a good pex pipe and go for it. Foamit UP


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## mike van (May 30, 2014)

velvetfoot said:


> Have people here used an equivalent amout of pex?  That's a big investment in copper.  As an aside, I just did my first pex plumbing job in the house, and it's very easy to do the joints.


                                                                                                                                                                                                                                                                                                                                                 With the cost of my install going to 15 thou. +  [Garn, building, plumbing] I didn't feel the need to cheap out on pipe.  Copper is forever, [my opinion]   plastic, well, who knows?  Has it been tested for 50 years?  When I was a 'new guy' at CL&P. someone made the decision to go with rubber ties to hold the wire on insulators,  10 years and thousands of rubber ties later, the sunlight broke them down, wire fell off the glass, burned down, tore bushings out of transformers, etc.   They saved some money when they bought those rubber ties though.


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## maple1 (May 30, 2014)

foamit up said:


> All my boilers have 1 1/4" pex in the long runs, once i got to the last 12 ft before the boiler i switch to black iron pipe. I just have a couple 90's before or after the pex joint to take up expansion. I have not notice any expansion in my systems and have not had any burst or broken pipes. Before crimp rings were so handy to get for this size i used double hose clamps on every joint with barb fitting. They are still working. So get a good pex pipe and go for it. Foamit UP


 

Ya - there is also a difference between near-boiler piping, and, well, not near-boiler. Maybe the OP could clarify some on what he's planning & his boiler setup - including overheat/heat dump setup. I don't think I would want PEX on the part of my system that is going to be dumping heat if needed - or near boiler.


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## brant2000 (May 30, 2014)

I agree with what everyone has said here...for most boiler installs copper would be the better (albeit more expensive) pipe choice.  With many other piping applications; however, plastic pipe is likely going to prove superior over time.  It really hasn't been around long enough to confirm this, but in place of what most steel/cast iron pipe has been used for, plastics (HDPE, PEX, PVC, etc.) will most likely last much longer and at a fraction of the cost.  Unfortunately most plastics show a significant strength reduction around 180-200 deg F, which is a shame.  Hopefully better high temp plastics will be developed soon.


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## tjvt (May 30, 2014)

maple1 said:


> Ya - there is also a difference between near-boiler piping, and, well, not near-boiler. Maybe the OP could clarify some on what he's planning & his boiler setup - including overheat/heat dump setup. I don't think I would want PEX on the part of my system that is going to be dumping heat if needed - or near boiler.


I got 2 legitimate estimates for boiler install. The plumber that quoted copper was significantly cheaper than the plumber who quoted pex. This was surprising to me, but struck me as a no-brainer...go with the guy who is going to use copper and do it for less money. Not being a plumber, I wanted to make sure I wasn't overlooking something. Still sounds like a no-brainer given the circumstances.


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## Highbeam (May 30, 2014)

The special tool for crimping pex rings is only 60$. Just buy it and you don't have to worry about this fear of having to go out and rent one.

I wouldn't use the PEX near the boiler for heat and expansion reasons but everywhere else it is great stuff. It has been in use for decades around the world. New tech is always slow to catch on but have you seen a plumber's truck lately? Not much copper anymore.


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## BoilerMan (May 31, 2014)

I love the look of copper, and it is 100% (if sweat and not pro-press) oxygen or any gas for that matter tight.  PEX still allows oxygen to pass through it and the higher the temp the more oxygen.  A radiant floor is a good application for PEX or any buried in concrete situation.  
PEX also as mentioned will not take long term high heat of a solid-fueled appliance for the long run, look it up on here it had failed in a power outage or a circulator failure (we all can have that happen).  Copper has been tested and had been installed since the 1940s and is still in service in heating systems from that era.

TS


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## Vizsla (Jun 1, 2014)

Copper or iron pipe all day long for near boiler piping. JMP, I almost always use copper for everything on the distribution , from boiler to zone valves or manifolds.


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## heaterman (Jun 5, 2014)

We always run copper or iron from the boiler to the main manifold area at the very least. The manifold itself where you will split off your zones should also be hard pipe. use Pex for your runouts to heat emitters if you want. It can be handy and there is nothing wrong with it when used in the right place or application.


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## velvetfoot (Jun 5, 2014)

I imagine that retrofitting pex might be easier.


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## Babu (Feb 17, 2015)

tjvt said:


> Aside from pex being a whole lot cheaper, any other advantages to pex vs. copper?


According to this study. Uninsulated 3/4" Pex-Al has a larger temperature drop than 3/4" copper! http://www.savegas.com/NewsArticles/HotWaterDist_Part4.pdf


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## brant2000 (Feb 17, 2015)

Babu said:


> According to this study. Uninsulated 3/4" Pex-Al has a larger temperature drop than 3/4" copper! http://www.savegas.com/NewsArticles/HotWaterDist_Part4.pdf


Interesting.  If true, it would make a great in-tank heat exchanger.


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## tom in maine (Feb 18, 2015)

I use PEX in our shop for testing. 
In my house, the boiler loop is copper. The distribution is PEX. Copper looks better and as long as it is not prone to freezing, it is going to be durable.
Since our boilers are unpressurized, I can boil the boiler loop and not think twice about it. (It makes for big fun!)


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## F4jock (Feb 18, 2015)

I use Pex now. Don't like to sweat fittings anymore. It's good to 180f at 100 PSI which suits my needs. Cut, slap on a Sharkbite and / or some SS flex and you're done. Copper looks better, sure, but I'm not going for house beautiful awards in the furnace room or behind walls. As for durability Pex should last long enough to outlive me. Copper may have some durability advantages at hogher temperatures and presdures tho, so if you're good with a torch, go for it.


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## dman_110 (Feb 19, 2015)

If you run into a freeze situation, you cant use a pipe thawer on Pex, you gotta locate it and hit it with a blow drier or some sort of heater. copper you can throw two clamps on and send some current through it, and thaw out the whole run. just a thought


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## davem3261 (Feb 20, 2015)

I used per for the 1st time for baseboard heat in my addition.   I did notice the ID of a 3/4 pex fitting was about the same size as 1/2 copper.   That's gotta hurt flow alot.   Pex was easy to work with wish I spent the extra money on the copper.   My boiler will creep up to 205 if it idles for awhile.   I hope it's never an issue if that zone calls while the Temps are higher than normal


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## Bob Rohr (Feb 20, 2015)

davem3261 said:


> I used per for the 1st time for baseboard heat in my addition.   I did notice the ID of a 3/4 pex fitting was about the same size as 1/2 copper.   That's gotta hurt flow alot.   Pex was easy to work with wish I spent the extra money on the copper.   My boiler will creep up to 205 if it idles for awhile.   I hope it's never an issue if that zone calls while the Temps are higher than normal




Determine what type of flow rates you need copper and pex tube have different ID.  Not a lot of selection in 1-1/4 pex fittings as far as tees and adapters.  Copper in sizes 1-1/4 and larger may pencil out less $$.

If you do go with large diameter pex, buy the straight 20 foot sticks


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## Highbeam (Dec 21, 2015)

Bob Rohr said:


> If you do go with large diameter pex, buy the straight 20 foot sticks



This is so true. I fought a coil of 3/4" in domestic plumbing and won't do that again. Way too stiff.


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## krinkov (Dec 21, 2015)

i used copper on my install in 1986 for the essex boiler now use the same copper pipe on the 140 woodgun in 2015.i use copper on everything then you are finished.


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## maple1 (Dec 21, 2015)

I have found though that you need to be careful with copper on DHW lines, particularly ones that hook up to a boiler coil. I had one spring a leak a few years ago, it was wasted away to not much, and when my father made changes on his a few years ago his were pretty well toasted too. Not sure if it's a chemistry thing, or a velocity thing, or a combination.


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## Pat32rf (Dec 23, 2015)

Copper is supposed to be the NOBLE metal but has proved to dissolve under the right conditions. This is why we now have to install coated oil lines to our furnace or water heaters in Ontario. In our area we have acid water and when we remove copper domestic water  lines that have been in service for 30 years they are very eroded on the inside. When I have a wall open I replace them.....
Some years ago I used to service electric water heaters and boilers. One sausage maker insisted on very pure water for his steam cooker. I had to replace his regular copper elements every year as they dissolved in the pure water. Don't know where the dissolved copper wound up.....


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## Highbeam (Dec 25, 2015)

Pat32rf said:


> Copper is supposed to be the NOBLE metal but has proved to dissolve under the right conditions. This is why we now have to install coated oil lines to our furnace or water heaters in Ontario. In our area we have acid water and when we remove copper domestic water  lines that have been in service for 30 years they are very eroded on the inside. When I have a wall open I replace them.....
> Some years ago I used to service electric water heaters and boilers. One sausage maker insisted on very pure water for his steam cooker. I had to replace his regular copper elements every year as they dissolved in the pure water. Don't know where the dissolved copper wound up.....



That dissolved copper stays in the water all the way through the sewage treatment process. I get called in to fix the water system when discharges from the sewage treatment plant contain too much dissolved copper. Never mind the compromised plumbing systems.


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## Pat32rf (Dec 26, 2015)

There used to be a geothermal system in our area (Ontario) where they would bury the copper freon coils directly in the ground instead of running antifreeze and another heart exchanger. You only needed a short run of copper instead of hundreds of feet of PVC.....From what the old timers say, the copper started to leak in about 15-20 years and needed to be replaced as it was paper thin.


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