pex tubing....

[mrcaptainbob]

I installed an OWB late 2004. Was told to use 1" PEX for the run from the OWB to the house. At that point it was converted to copper. Two years later I installed hydronic heat in the up and downstairs baths, using 1/2" PEX. I was recently cautioned that the use of standard white PEX for the floor heat was not a good idea and will fail in the future. And that I should have used the 'appropriate' hydronic PEX for that part. Of coarse I can uninstall what is there and replace it all, but is that really necessary? If it comes apart in the floor, why would I have confidance in what is buried four feet in the ground? It's still running the same hot water.

[HayZee518]

Materials = pvc, cpvc, polyethylene. All I've ever seen for heat or domestic hot water is grey tubing.

[mrcaptainbob]

PEX info...

Hi, HayZee. I kniow the red and blue PEX is used for domestic potable systems. And I think the orange stuff is supposed to be the PEX of choice for hydronic systems. I used the white PEX and am wondering about it's life expectancy.

[HayZee518]

searching a few pex sites brought up life expectancy - how's 200 years plus sound? non exposure to uv light [sun] yielded the 200 yr figure. any color of pex with proper fittings.

[mrcaptainbob]

Pex

Hmmmm. 200 years. Of coarse, it is where the sun don't shine.
Thanks for the help, HayZee. That eases my mind.

[Redwood]

Hope you are still watching this thread mrcaptainbob.

The problem with PEX for hydronic applications is that you do need a special PEX!

PEX tubing will allow some things to pass through the cross linked polyethylene and the problem is that oxygen will enter the system. The special PEX for hydronic applications has an oxygen barrier that that will prevent oxygen from entering the water.

Failure to use PEX with the Oxygen Barrier will result in your cast iron boiler rusting out. along with any iron fittings used in the system.

The water in a hydronic system rapidly looses its oxygen and unless there is a leak in the system and water is added frequently or, PEX without the oxygen barrier is used corrosion in a system is almost non-existent.

Oxygen Barriers

Some applications require PEX with added oxygen barrier properties. Radiant floor heating (or hydronic heating systems) may include some ferrous (iron-containing) components which will corrode over time if exposed to oxygen. Since standard PEX tubing allows some oxygen to penetrate through the tube walls, various "Oxygen Barrier PEX" tubing has been designed to prevent diffusion of oxygen into these systems. Two types of specialty PEX pipe are offered:

1. Oxygen barrier PEX has a layer of polymer laminated to the outside surface (or sandwiched internally between PEX layers) that prevents oxygen from penetrating. The polymer film is usually EVOH (ethyl vinyl alcohol copolymer), used in the food industry as an oxygen barrier.

2. PEX-Al-PEX (or PEX-Aluminum-PEX or "PAP") is a specialty PEX tubing manufactured by several suppliers. This tubing has a layer of aluminum embedded between layers of PEX to provide an oxygen barrier. PEX-Al-PEX may also be called multilayer pipe or composite plastic aluminum pipe. PEX-Al-PEX will also retain shape when bent, and may also exhibit less expansion and shrinkage during temperature fluctuations, but may be less flexible than PEX tubing. PEX-AL-PEX costs about 30% more than standard PEX. http://www.pexinfo.com/

[mrcaptainbob]

Pex....

Thanks for that info, Redwood. Great info. I may be in the clear then, as I am using the Central Boiler brand 1650XL Inhibitor Plus (Inhibitor plus Polymer Solution) [p/n 1650]. It is what's recommended By Central Boiler and we make sure ph is balanced per their charts.