Under cement floor pipe for heating

Ruthgirl

My contractor laid zurn 3/4 inch Pex tubing under my basement cement floor.  He said it was rated for 200 degree water and that it contains an oxygen barrier.  It runs the span of the wall which is approximately 10 feet.  My inspector looked at the pipe part that sticks out of the cement floor and said it does not contain an oxygen barrier and it is not insulated.  In this situation what should I do?  Is it necessary to have an oxygen barrier and insulation or due to the short span of the pipe, is it ok as it is?  Should I have my contractor redo it?  Thank you for your reply.

CMadatMe

Here's the deal

My first question is...How did the inspector identify that tubing to not have an oxygen barrier?

An oxygen barrier tubing is required in a heating application. The reasons is oxygen can find its way through the tubing. This can cause all ferrous material (iron) in the system to start to rot from the inside out. This was 1st discovered back in the 70's  in the Northwest part of the country. There, they were using poly-butelyne (may not have spelled it correctly)  tubing in radiant heat applications and what they were finding was that the ferrous materials in the systems started to fail.

I don't believe 10 feet is going to cause a problem in the short/medium run but it will have some effect but to what effect I couldn not tell you.

hot_rod

so...

sounds like you need a 3rd opinion to see if it is barrier or not?



If it is non barrier a heat exchanger separation is a do-able option. Or all non ferrous components in the boiler, pump, expansion tank piping.



The installer that told you it is barrier tube should pick up the cost of the HX and non-ferrous pump, etc. IF in fact it is non-barrier tube.



Not sure what you mean by insulation? Under the slab or around the pex penetrations through the slab?



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JerseyWreckDiver

Non Barrier Pex.

Her inspector knows because he has installed a substantial amount of radiant heating himself over the years.



I'm going to stop talking about myself in third person now, because it's weird.



I also know, because it looks like this. Last I checked, Zurn only makes white tubing in Non-barrier grade. And unless someone is producing one I haven't seen yet, totally possible, O2 barrier tubing shows two distinct layers in the cut end, 3 if it's Pex Al Pex or Alumi Pex.



Now, what happened here is that the tubing was laid in a trench that happened to be open for a sub-slab drainage system cause it was a convenient way to get from one side of a fireplace to the other with the baseboard run, so it's not an entire system with non barrier Pex, it's about 10 - 12 feet of tubing. Standard, cast iron heat exchanger boiler. Is the amount of oxygen that may come through this going to be a real problem? I'm not certain, which is why I suggested the OP come here.

CMadatMe

Was Just Trying to

asertain how you identified the tubing because at times the writing on the tubing isn't clear enough or there is not enough exposed to get a clear reading. By your pic you can clearly see that it is potable tubing. While you did pick up on this I also picked up and would be concerned that this tubing isn't sleeved exiting the concrete. Expansion and contraction will happed at the point closet to the slab thus in time possibly wearing the tubing and causing a leak.

Like I stated in my previous post...While not using oxy barrier tubing is a no,no  I don;t think 10' will have an immediate impact but will over time have an effect on the ferrous materials in the system To what extent I can not tell you. I don't think anyone can..Never seen a study on effects based on length of non-barrier tubing installed in a heating system. 

EricAune

Replace it

The easiest fix for the problem would be to replace the tubing now.  Concrete is not a permanent surface, is easily removable in most cases.  The same can not be said of a corroded cast iron heat exchanger, air scoop or any amount of black iron piping.



The contractor either did not know the truth and reasoning behind the type of tubing needed.  Either way, it sounds as if you might think of interviewing another contractor, you might find the first one is not as qualified.



Insulation is a definite at point of pass through.  Should be insulated for its entire length if its not being used as a emitter. 



Peace

hot_rod

moving how many BTUs?

1/2" pex would easily slide inside 3/4" over that length. With a bit wider delta T you could move 20,000 BTU, or more through 1/2".



But as suggested the correct way is to install insulated 3/4 barrier pex, if that is what the load requires.



In a trench with sub-surface drainage?? The tube must be in a dry trench or BTUs will wash away, even with insulation. Maybe an overhead route would be better?



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Jean-David Beyer

Non-barrier tubing..

It is my understanding that some air separators, such as Taco 49-125 (that I have) and Spirotherm VJR-1C extract air, microbubbles, and some dissolved gasses (such as oxygen). While I would not advocate using non-barrier tubing for an hydronic heating system, should not such an air separator work for just a short piece of the wrong tubing? Presumably these things can reduce the dissolved air in the water to less than 0.5% I guess the question relates to the rate of air transfer through the tubing and the rate of air removal by the separator; can the separator remove the air at least as fast as new air diffuses into the tubing.

hot_rod

non barrier may void

the warranty on the boiler.



Chemicals are another "fix" but an ongoing one. Oxygen scavengers can be added but they get used up and need a boost. That's a common method for open system outdoor wood boilers, keep dumping in the juice.



The amount of O2 ingress is related to the operating temperature, hotter systems inhale more than low temperature.



Hard to predict exactly how much of a problem it will be with so little pex, but why risk it.



They make barrier pex and radiant tube for a good reason.



We've paid a very expensive price to learn that lesson. Ask Goodyear and any former Heatway, SolarRoll and PB and installer



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Jean-David Beyer

hotter systems inhale more than low temperature.

Are you sure about this? If we were dealing with just water in contact with oxygen, the reverse would be true, since gasses are usually more soluble in colder water (until it freezes, anyway). So if you are correct, it must be that the tubing is more porous at higher temperatures, more so than the decrease of solubility of the oxygen in the water.

hot_rod

Tomas Lenman

wrote an excellent book on PEX tubing when he was with Wirsbo. Looks like he has this book downloadable at at his website.



He knows and knew what was about to happen we we started installing non barrier tube, back in the day.



I believe he covers O2 issues in the book, or google around for other articles on the subject.



I know the high temperature HW baseboard systems deteriorated much quicker than low temperature radiant, with non barrier tube installed.



www.mrpexsystems.com/waterpipes.asp



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