Manabloc Supplying Cold Water Non-Oxygen Barrier Pex Mix & Radiant Heating
Last Post 16 May 2014 07:31 AM by dave111. 8 Replies.
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clovesUser is Offline
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10 May 2014 09:24 PM
Hi everyone,

I have a closed radiant heating system and I had an question about pex tubing that popped up. Our water main is getting fed into a water filter and then into a 30 port manabloc. The manabloc will provide our domestic water for all of our fixtures. The manabloc has a cold feed through at the bottom which is made to feed the water heater. We will be running 3/4 barrier pex to the water heater and 3/4 barrier pex back to the hot intake on the manabloc.

The 1/2 feeds for the fixture will be non-barrier pex. My question is will the non barrier pex on the cold side from the fixtures send oxygen molecules into the the cold feed through supply of the manabloc? This of course would introduce oxygen into the radiant heating system which would be a bad thing.


sailawayrbUser is Offline
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11 May 2014 01:34 PM
Manablocs are typically used for plumbing domestic water and not typically used for plumbing HR. Where exactly is your HR system (i.e., emitter loops, circulator(s), etc)?

Yes, oxygen will go through PEX that does not have oxygen barrier. Yes, oxygen can be bad for HR system components if they are not brass or stainless steel. However, it isn't clear to me that this non-barrier PEX is even part of your closed HR system.
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newbostonconstUser is Offline
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11 May 2014 09:49 PM
As far as I know oxygen barrier pex is not to be used with potable water.
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sailawayrbUser is Offline
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12 May 2014 11:00 AM
Domestic water plumbing is an open system and there will always be oxygen in the water anyhow. So there is no need to use oxygen barrier PEX for domestic water plumbing. Oxygen barrier PEX can be used for domestic water plumbing, but there is little point for using it…so save your money…
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Eric AndersonUser is Offline
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12 May 2014 12:49 PM
If the tank in question is an indirect storage tank heated by your boiler as a zone. Then what you show is fine. You don’t need to run the 1” pex through the manbloc to the indirect tank. You can Tee it off above the Manblock because the bottom port does not have a valve, and you want a shut off valve before the tank. Depending on what your heat source is, you might want a mixing valve on the hot water output of the tank. Ideally you only want the hot water out at ~120° deg Since the DHW is constantly getting new- oxygenated Water, the oxygen barrier is not necessary- but it does not hurt. IF you are using the manbloc as the distribution for radiant heat also, you need to rethink what you are doing.
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newbostonconstUser is Offline
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13 May 2014 01:56 PM
The chemical that they use to make the oxygen barrier when manufacturing the pex often makes water taste bad....and many manufactures have printed on the pipe "not for potable use" please make sure the pex is for potable use before using it...
Posted By sailawayrb on 12 May 2014 11:00 AM
Domestic water plumbing is an open system and there will always be oxygen in the water anyhow. So there is no need to use oxygen barrier PEX for domestic water plumbing. Oxygen barrier PEX can be used for domestic water plumbing, but there is little point for using it…so save your money…


"Never argue with an idiot. They will only bring you down to their level and beat you with experience." George Carlins
sailawayrbUser is Offline
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13 May 2014 02:57 PM
Accomplishing the necessary testing to obtain a potable water certification rating costs many dollars. PEX manufacturers do not often apply for potable water certification for their heating system oxygen barrier PEX products because they are already more expensive PEX products than their cheaper domestic water PEX products even before obtaining the unneccessary potable water certification rating, and not many people are going to use these more expensive heating system oxygen barrier PEX products for plumbing domestic water.

We are not aware of any harmful effects from the use of ethylene vinyl alcohol (EVOH) applied to the outside of heat application PEX as an oxygen barrier. If anyone has definitive information about this (i.e., other than urban legends based on the box stating not certified for potable water use), please share it. Nevertheless and again, only someone who really wants to spend more money than is necessary would ever use heating system oxygen barrier PEX for plumbing domestic water, whether it has a potable water certification rating or not. You also likely won’t pass a domestic water plumbing inspection if you use a PEX product that does not have a potable water certification rating.
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FBBPUser is Offline
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13 May 2014 07:51 PM
Barrier pipe is often used for potable water simply because there was twenty feet or so left over from the floor loop.
dave111User is Offline
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16 May 2014 07:31 AM
I used it for the toilet feeds as it was certified, and it wasn't blue, it was a better fit with the color scheme. And, as was noted earlier, I had some left over from the floor loops.
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