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Old 09-25-12, 03:04 PM   #1
Daox
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Default Iron pumps & oxygen barrier pex

I'm looking for opnions. I bought 300' of pex tubing last night and I'm not even sure if it has an oxygen barrier or not. I know if it doesn't, I shouldn't use a cast iron pump which is cheaper than bronze or stainless. I'm looking for opnions on if its worth trying to use oxygen barrier pex or just go with a bronze or stainless pump? I imagine even with the oxygen barrier the iron pump will still go bad eventually, and by the time you pay for a 2nd pump (dunno about rebuild kits), you're a good way to the price of a bronze or stainless pump, and maybe beyond it.

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Old 09-26-12, 01:19 PM   #2
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Quote:
Originally Posted by Daox View Post
I'm looking for opnions.
O2-barrier PEX can be PEX-AL-PEX, which has an aluminum layer. O2-barrier PEX can also be O2-barrier coated.

If you have colored PEX it is almost certainly O2-barrier coated. The O2-barrier coating is not 'slick', but rather tends to have a slightly 'tacky' surface texture. You can tell the difference with your fingernail.

If you have white, there is a good chance that it is NOT O2-barrier... but it is possible that a transparent O2-barrier coating has been used. Use the fingernail test.

To make matters more interesting, there is even coated PEX that is O2-barrier, and has a final non-tacky layer on the outside, so it is PEX + O2-barrier + PEX... the reason for this last type existing is there seem to be some problem with 'popping' sounds when O2-barrier PEX is used with aluminum plates, because the 'tacky' coating tends to grab & release the PEX with temperature changes (PEX tends to change about 1" / 10 degree F / 100').

I have poured over quite a bit of literature regarding radiant floor installation practices in the US over the last 60 years or so. Some of the advice you come across should be viewed through a historical filter.

One thing that doesn't change, and that you should keep in mind is that if there is any tendency toward galvanic-action erosion, it will be accelerated by constant flow.

Early radiant floors were plumbed with iron pipe in concrete, and used iron pumps. there are numerous references to "black water". This referred to the color the water gets after having circulated for several years. It was considered a good thing, as the water had reached the maximum rust carrying level it could reach, and further corrosion was not going to happen... or so they thought.

Relatively recently, the European innovation in plastic pipe (PEX) has become the mainstay in the US. The new rules of thumb seem to be:
  • Open Loop... (heating water also used as DHW) don't really need O2 barrier, as there is already so much O2 in the water already, and the O2 is constantly replenished. Iron pumps will have short life... bronze & stainless are best.
  • Closed Loop... O2 barrier required, iron pump OK as long as there is not a galvanic action metal (like ANY bronze) in the system. If there is only stainless, it is not so different from iron.
  • Safest & most expensive is to use O2 barrier and bronze pumps. If you have too much money, go with stainless.

Best,

-AC
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Old 09-26-12, 02:36 PM   #3
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Well, the tubing is red in color, but the manufacturer (nibco) doesn't specifiy an O2 barrier on it. This leads me to believe that it doesn't have one unless its burried amongst one of the handful of ASTM specs. Here is the mfg page. It does not have a tacky coating, it just seems smooth to me.

NP60 Coils - PEX Tubing

I purchased my 300' at the local Menards for $240. Just today, I found that I can get 300' of 1" PEX with an O2 barrier from pexuniverse.com for about $195. So, I'm inclined to return it and order the PEX online. I was planning on ordering pex crimp fittings from them anyways for connecting the solar panels.

Talking with a friend at work, he said the iron pumps can last quite a long time, around 15 years. At which point you can get a rebuild kit for roughly half the price of the pump. Once you buy a rebuild kit, you're at the price of a stainless pump (no bronze option). I think I can probably handle a rebuild every 15 years.
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Old 09-26-12, 07:09 PM   #4
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Quote:
Originally Posted by Daox View Post
It does not have a tacky coating, it just seems smooth to me.
Well, the 'tacky' coating is not actually sticky. It's more like if you were to slide your finger nail across the surface, it isn't real slick. By comparison, the non-barrier PEX will feel 'self-lubricated' like nylon bearing material if you ever experienced that.

NP60 Coils - PEX Tubing

I'm challenged as a reader... you can probably read better than I can. If you can't find it, I probably can't either.

Quote:
Originally Posted by Daox View Post
I purchased my 300' at the local Menards for $240. Just today, I found that I can get 300' of 1" PEX with an O2 barrier from pexuniverse.com for about $195. So, I'm inclined to return it and order the PEX online.
Better, cheaper... no challenge there.

Quote:
Originally Posted by Daox View Post
I was planning on ordering pex crimp fittings from them anyways for connecting the solar panels.
I took a solar installer certification course, and they were rather deprecating regarding the use of PEX for solar. They recommended copper. However, at the prices charged for copper vs. PEX, I can understand your choice.

Quote:
Originally Posted by Daox View Post
Talking with a friend at work, he said the iron pumps can last quite a long time, around 15 years. At which point you can get a rebuild kit for roughly half the price of the pump. Once you buy a rebuild kit, you're at the price of a stainless pump (no bronze option). I think I can probably handle a rebuild every 15 years.
I bought a used iron pump that had been used in a heat pump DHW application for two years. I opened it up, and it was clear that it wouldn't last another two years.

Beware of dis-similar metals in your system(s)... like copper collectors & iron pumps. Or brass fittings & iron pumps. Galvanic action will win in the long run.

Best of luck to you...

-AC
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Old 09-29-12, 06:46 AM   #5
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OK, some companies, such as Nibco and Bow make their PEX primarily for domestic water and colour it red or blue for hot or cold, not because of O2 barrier. O2 barriers are different depending on the manufacturer. The REHAU stuff feels nothing like the WIRSBO stuff so you have to look up the part numbers. Al least in Canada, HD or Lowes don't sell O2 barriered stuff because they cater to the plumbers more than the heating guys.

AC is right, though, the P-AL-P stuff has an internal barrier.

Most pump stations for solar come with cast iron pumps and that is NOT a problem. It will last for decades. The issue is oxygen. If it is kept out, the existing O in the water deposits itself on the sides of the piping, pumps and everything else and you then have an inert fluid. I have taken the water out of 60-80 year old heating systems and aside from it being black and stinky (cast iron rads and copper piping), everything was great.

PEX allows more O2 to come in than copper or steel so it will be a problem in the future....distant future.
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Old 10-18-12, 08:36 AM   #6
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Thanks guys. I did end up returning my nibco tubing and purchased the 300' of oxygen barrier pex tubing from pexuniverse.
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Old 10-18-12, 06:21 PM   #7
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Great, you won't regret it.

BTW, there was an early post from AC (I believe) asking if you were going to use a "drain down" system with vacuum breakers. You were not doing that, which is good, and drain down systems have fallen out of favour because of solenoid failures that allowed water to stay in the pipes and freeze.

"Drainback" systems should NEVER have an auto air vent or vacuum breaker at the top of the system, unless all components are non ferrous. Even then it is not necessary and should be avoided. The water will trickle back to the tank over time, long before any freezing can take place.

Sometimes I am not sure if people know the difference between "drain down" and "drain back".
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Old 10-18-12, 06:39 PM   #8
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I've actually never heard of a drain down system. Is that a closed loop system that isn't full of water?
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Old 10-18-12, 07:32 PM   #9
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It's a system where a solenoid opens from the tank and potable water is filled up to the panels when the control calls for heat. The pump then starts and circulates the water directly from the tank through the panels and back to the tank. When it is too cold out, some solenoids close and some others open and the potable water drains out and down the drain. It is a bit wasteful of water but it was very efficient because there is no HX and only one pump but sometimes the solenoids would fail and the panels would freeze.

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