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.
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
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
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., ...
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.
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.
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.
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.
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
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?
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
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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