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Old 09-27-13, 12:28 PM   #1
Daox
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Default What kind of PEX tubing for hydronic heat?

What kind of tubing have you guys used in your hydronic floors? I realize you need an O2 barrier of some sort if you want to go with an iron pump. But, beyond that, is there any other considerations?

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Last edited by Daox; 09-27-13 at 12:31 PM..
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Old 09-27-13, 04:51 PM   #2
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What kind of tubing have you guys used in your hydronic floors... is there any other considerations?
If you're using aluminum plates, there is the possibility of pipe expansion & contraction noise (AKA: 'popping'). As far as I can tell, the noise is a result of the 'tackiness' of the oxy-barrier coating grabbing and letting go of the aluminum, and not all coatings are the same.

Mike Mobile Mechanic reported that he found a pop-free brand, that he recommended. If you decide to go with uncoated PEX, it is pretty slippery and not likely to pop. Also, with PEX-AL_PEX, the aluminum acts as an oxy-barrier, and the outer PEX is not coated... but you lose some tightness of bend radius with PEX-AL_PEX

As I recall, one of our Norwegian posters said that they used some kind of thin cloth sleeves over the PEX to prevent popping. I never heard of that anywhere else... but there you have it.

But if you use bronze pumps, and have no iron in your circuit, or sensors or valves, you shouldn't need an oxy-barrier at all, so no coating would be required.

If you go with Uponor PEX, they offer a special expansion tool that only they can $upply... although you ought to be able to use one of the ring systems, too.

Some of the radiant floor 'trade-lore' carries forward from the days of iron pipes, where iron pumps made perfect sense. Good luck.

-AC
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Old 09-29-13, 09:27 PM   #3
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Just to clarify some of AC comments, any of the the so called "1/2 inch" PEX tubes can use each others fittings as they all meet the CSA/UL standard. REHAU (my favorite) and Wirsbo (Uponor) are made the same way and have the same sizes (SDR9). Crimp fittings work on both as do as will compression fittings.

A word about O2 barriers. They are not all created equal. The REHAU barrier allows less O2 through the wall than the Uponor. Uponor used to have a tube called PE-PEX with 3 layers of O2 barrier but to compete with REHAU and Heat-link (back in the day), they dropped the layers to 2 (HE-PEX) which has slightly less protection.

No tube is impervious to O2, not even the Pex-al-pex. When the tube is bent, the AL can separate on the bend. It is a small opening but O2 can enter.

I have 15 - 20 year old boiler systems with this tube and there is often sludge in the tubing. This is true of any PEX tube, and it is only a matter of time before some sludge or corrosion is evident. It may take years. In extreme cases, the sludge due to filling and draining and filling again can clog up a pump, bronze or iron body.

My advise is to always use an O2 barrier tubing for any closed loop system. Penny wise and pound foolish.
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Old 09-30-13, 12:40 AM   #4
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My advise is to always use an O2 barrier tubing for any closed loop system. Penny wise and pound foolish.
So if you have made the decision to use stainless HXs and bronze pumps, what does oxygen barrier PEX actually do for you?

And the sludge you are describing, where does this come from? I know that in the iron pipe days, sludge was a fact of life, but where would it actually come from? Is it bacteria growing?

Sounds like an in-line filter would be a must.

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Old 09-30-13, 06:09 AM   #5
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I have taken apart 100 year old steel pipe systems and the inside of the the pipe is pristine because no O2 got in there to cause rust and unless there is consistent leaks it will be good for another 100 years. Steam systems are a different matter entirely.

There won't be bacteria because there is no food for it and it needs an O2 environment. Most sludge is particulate matter in the water, pipe cutting oils or rust from any iron or steel component and even if some parts are brass, there may be a steel mesh or pin in it. Even smaller amounts can sometimes get into a pump bearing and seize it up.

In the heating trade we know it is just good practice to try and keep the whole system O2 free.

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Old 09-30-13, 08:47 AM   #6
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What if I installed one of those O2 vents inline with the pump? Would that be enough or a good idea?

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Old 09-30-13, 08:55 AM   #7
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An air eliminator is always a good idea but don't confuse O2 migration with air. The O2 will diffuse in the water and bond to whatever sediment or particulate that floats around the system. Air will raise up to the highest point to be vented (hopefully)

I don't get the desire to not buy O2 barrier pipe. Tubing is cheap these days and if it is the difference of $.05/ft, what should it matter. It is extra protection.
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Old 09-30-13, 11:11 AM   #8
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Just to clarify some of AC comments, any of the the so called "1/2 inch" PEX tubes can use each others fittings as they all meet the CSA/UL standard.
I edited my post to say that Uponor "offers a tool"... It's not required.

But, on the Oxy-Barrier issue, I have searched high and low for something that resembled science regarding the oxy/no oxy issue, and this was as close to science as I could find:

Quote:
Q. Do I need an "oxygen barrier" tubing?

A. Studies indicate that if water temperatures remain below 140 degrees, no significant amount of "oxygen diffusion" will occur. An OPEN system using a stainless steel water heater (i.e. Polaris) as a heat source will suffer no negative effects from oxygen diffusion in any case. However, radiant systems using higher water temperatures would probably benefit from oxygen barrier tubing. So would a steel boiler in a CLOSED configuration because that type of boiler is more vulnerable to oxidation than a cast iron boiler. As a result, oxygen barrier tubing could prolong the life of the boiler.

In addition, some municipal codes simply require oxygen barrier tubing in any radiant system. This despite the fact that none of the experts seem to agree on how much, if any, damage is being done to the radiant system. As mentioned above, at normal, low radiant temperatures, oxygen diffusion is minimal. Is it worth spending more on tubing in order to, maybe, prolong the life of the system? Especially since non-barrier tubing has been used for years in low temperature systems without any reports of accelerated damage.
Radiant Heat From Radiant Floor Company - Radiant Heating FAQ
Early failure in steel expansion tanks does seem to be a oxy problem, but apparently by using a potable water expansion tank with non-barrier tubing seems to do the trick.


But I'm still curious about the sludge thing...

Could it be oxy reacting with anti-freezing additives?

-AC
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Old 10-01-13, 07:45 AM   #9
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AC,

Sludge in plumbing (of any kind) comes mainly from two places: impurities in the water and pH imbalance.

In recirculating systems, impurities build up as water is added. The system burps, water leaches or leaks out, valves hiccup, etc. Makeup water is usually added from the municipal tap, which contains lots of trace elements dissolved in it. Also, everything corrodes or dissolves eventually as long as there is heat and flow. Iron rusts, dissimilar metals electrolyze, plastic chafes or bleaches, and when the temp goes up and down the expansion and contraction dislodges the stuff. Then the stuff goes round and round in your system until it settles. Somewhere.

pH is the other culprit. Low pH is bad for the plumbing, since acid eats metals. Too high pH is bad for the water, since the impurities begin to form scale. Actually, glycol is somewhat basic and absorbs oxygen as it ages. However, when it gets old, the pH drops and the corrosion inhibiting action is neutralized. Then the impurities have their way with the system as above.

The easiest way to prevent all sludge-related problems is by doing occasional inspections or pm's. A ten dollar pool water test kit will tell you how your water is, along with a visual. Just drain out a quart and have a look at it. Kind of like checking the coolant in your car.

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Old 10-01-13, 08:19 AM   #10
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I have a Ph meter and regularly test glycol in solar systems and heat pump ground loops so, yes, it is essential to do so at some intervals. Solar systems should be done annually but ground source run at lower temps so I have seen glycol last 10+ years.

Many years ago (20 or so IIRC) I got ahold of the test data for barrier and non barrier tubing, both Wirsbo, REHAU, and Stadler and a couple of others as almost all were European made at the time and noted which ones had the lowest rates of diffusion. There is a few reasons why non barrier systems are not done in Europe and one of them is about liability. The contractor is responsible for the system for many years after installation and there is a great reluctance to have to go back and remedy something done 10 years previous.

I was once a witness for a big boiler company in court, when a homeowner sued said company because the cast boiler rotted out in 3-4 years. The HO was instructed to put in barrier tubing but to save money, put in non barrier. We were able to show that the O2 migration caused the failure and that it was not the responsibility of the boiler company. The tubing was tight, without leaks over the period so a massive amount of sediment was not the issue.

Some people do say that will all non ferric components, this shouldn't matter but to me a pump (for example) should last 40 years. In closed systems they do and in open systems, they usually don't. To me an closed, non barrier system is half way between an open system and a closed system with barrier tube. The standards describe the amount of diffusion over a period of time but we have to remember that the tubing is to be there for 50+ years.

Jeff has some good points, but my point is that we should design the system, not to be "good enough" but to last a long long time and good engineering means mitigation the effects of known issues. Barrier tubing is a no brainer.

As a side note, I think some companies will have more tube sales if they sell a slightly cheaper product so that might sway their opinions.

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