Oxygen In Radiant Floor Heating

My expansion tank rust out in about 1 year.replaced 3 in about 4 years.I've been told its high oxygen in the water .How can I get rid of it.
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BOB1901

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Is the system open or closed?
It sounds to me like it's an open one and uses a expansion tank designed for a closed system.
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HeatMan Wrote:

This is a radiant floor heating system. The sys has an air eliminator,operating pressure is around 15-20 lbs,temp is about 130 degrees and closed sys.The sys uses a hot water tank to heat the water. I had tried anti freeze to act as a lubricant to stop the rusting of the expansion tank (mixed a few gallons in to the sys),no luck. It seemed to make the expansion tanks rust faster.First tank lasted about 18 months,second about 12 months ,third about 9 months. Any way of reducing the oxygen in the water.
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BOB1901

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BOB1901 wrote: ...

What does the installer say? Surely yours isn't the only one they've done. What is unique about yours? If everybody has the same system, they all should have similar problems. Failing help from the local installer, have you contacted the system manufacturer for advice? There are lots of radiant floor heating systems in use and I've not heard of this being a generic problem so _something_ must be unique here.
I've no direct experience w/ one of these systems, but I'm puzzled as to how you're getting such high dissolved O2 to begin with. Is the water heater electric, perchance, and you're getting localized boiling off the heating elements continually generating the dissolved air? Is there some local cavitation in pump doing something similar?
To minimize dissolved O2/air, if the system is filled and left open to atmosphere, eventually it will come to an equilibrium point. This could be accelerated some by pulling a slight vacuum on the system to lower pressure (opening the pop bottle effect).
What's the rest of the piping, why isn't there a problem elsewhere in the system? Also, replacing a steel tank (apparently unlined) tank w/ a stainless or lined one should elminate the problem from a different angle.
I'd surely want to hear more from the system installer/manufacturer on why I was having such problems if nobody else is--or what they're doing for everybody if I'm not unique...
Just my $0.02, IMO, YMMV, etc., etc., ...
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dpb Wrote:

The sys has about 400 feet (4 separate runs) of PEX tubing (orange plastic tubing-designed for this sys,no oxygen barrier).I installed the sys (DIY),with help from manufacturer,company in Vermont,US. I spoke to them and they don't have any idea.Other sites have said the problem is no oxygen barrier in the tubing.I was told I didn't need one since I was using a gas hot water heater. Can't change the tubing so trying to find way of lowering the oxygen content.The only other idea was a plactic lined expansion tank.The problem is will the oxygen attack the copper tubing or the water heat if not that. Thanks for any help.
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BOB1901

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Now it becomes clear..

400 foot runs? What kind of pump do you have, a Taco base mounted one? Pros never go over 300 feet.

As I said, get an expansion tank for a potable water system. If you put anything at all in the system, such as an oxygen scavenger, you'd better have a double check valve or a back flow preventer on the system. Otherwise, you may end up drinking, cooking with, or showering in your oxygen scavenger. Betcha the Vermont company never told you that.

Friend, your main problem was that you went with the possibly worst company on the 'net. Sure, they were a lot cheaper than having a pro do it, but look a the problems you've been having. That company sells rubber stamp systems and their tech support is actually non-existent. They have your money and don't really care for you any more, so they have no clue of the problem you're having, even if they just got off the phone with the exact problem with another customer.
Was an accurate heat loss done? A standard gas WH has an input of about 40K BTU's. That may take care of and area of between 600 and 1000 square feet. That ain't much.
Good luck. Go to the Wall and ask them about the Vermont company. http://forums.invision.net/Main.cfm?CFApp=2
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On Thu, 7 Sep 2006 17:57:43 +0100, BOB1901

I've thought long and hard about this and have come up with NO IDEA how someone dreamed up one is a factor of the other.

You'll need to find a reputable chemical-man/water treatment company (good luck on that. Ask some of the local manufacturing companies who they use for their boilers and cooling towers) and have your boiler water treated properly. Not a big deal.
-zero
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zero wrote:

In a closed system, and this one should be, distilled water has no excess oxygen almost by definition.
So long as the boiler does not heat the water to more than about 150F, no steam bubbles either
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dpb wrote:

Another solution is to look for a Well Mate tank, all fiberglass tank with REPLACEABLE bladder!!
Model WM-4 is 16 inches in diameter and 22 inches tall.
More expensive, but if you get 20 or more years of life out of it????
MFG List for a 14.4gallon tank with 30/50 draw down of 4.4gallons is $275. Online retailers will discount to roughly $155. Interestingly enough, a 20gal tank is $5 cheaper in some cases.
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Next question. Do you know the name on the tubing?
Easy answer. Whoever did the install used non-barrier tubing. There is virtually nothing that can be done as far as an oxygen scavenger that will last.
My suggestion is to use an expansion tank for potable use.
Who installed the system? Was it one you got off an internet sales site?
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32094

Hello Bob,
The corrosion in your expansion tank is due to dissolved oxygen in the fluid attacking ferrous materials including the tank, circulating pump and any other steel or iron component. The flexible radiant floor pipe you used did not have an oxygen barrier to protect the system. The oxygen passes through the wall of the tubing due to an imbalance between the closed heating system and open oxygen rich envirnoment in our atmosphere.
If your floor heating system is connected to your hot water tank and the DHW plumbing system just change the tank to the amtrol or equivalent listed below. If your radiant system has a dedicated heat source in other words it is a closed system your may have other issues and components to change.
To eliminate your problem replace the expansion tank with a model suitable with potable water systems such as the amtrol ST5 or ST12 and replace the circulating pump with a bronze or stainless steel model. Your goal is to replace any component not suitable for open potable applications. If your system was installed by a professional plumber go back to him to remedy this problem or if this was a DIY project then contact a radiant heating designer at your local plumbing wholesaler for help.
If your heat source is a steel or cast iron boiler this item is also being attacked. Your solution will also require a stainless steel heat exchanger to isolate the tubing system from the heat source. Talk to a professional in the future.
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And you're JUST finding this thread?
The question was answered a long time ago.....

used
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