I had to replace a Water Heater over at My Moms House. I was going to use PEX for the Flexiable Lines coming off of the Water Heater.

I have no experience with PEX and when I first read up on it said the PEX could be used for Hot Water Lines.

The next day when I did more research 2 sites said the PEX could not be used as a direct connection to the Water Heater. One site said the PEX had to be 18 inches away from the Water Heater and the other said I think it was 2 Feet.

If you keep it away from direct Contact of the Heat Source it could be used for Hot water.

There is also another Type of PEX that has some sort of exterior coating that acts as an Oxygen barrier. That PEX can be used to be cast into Concrete under the House to act as a Floor Heater for the House.
PEX Information
"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."


The PEX sold at the local Home Depot said on the Box it did not have the Oxygen Barrier.

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84 300D, 82 Volvo 244Gl Diesel

Thanks for all the advice. Turns out when I got over there, despite the plumber's claim that all the valves needed to be replaced, that his only problem was a couple of the valves were leaking around the o-ring seals. the motors were fine. So we pulled the valves, swapped in new ones and reinstalled the motors. Valves were a little pricey at $40 each but better than a $1500 plumbing bill. Filled the system using Brian's instructions. It's back up and running.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Cool!

(or should I say Hot!)

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Excellent.

Can you change the valve on those without sweating in an entire valve assembly?

$40. is cheap. The Honeywell valves are usually about $70............sometimes you can get one for less on e-bay.

Yep. Valves have a bayonet system which attaches them to the body. You can even install a seal kit to stop leaks. It wouldn't have worked in this case because they had been leaking for so long that everything was corroded on the outside and one valve body broke as I was pulling it out with a vice grips. Took about an hour to swap out two valves including extracting the broken valve and cleaning up build up in the body of the valve.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Interesting.

I wasn't aware that the White Rodgers valves had that flexibility.

The Honeywells (I have nine of them) have proven to be durable performers with only two motor failures in about 10 years.