Two questions about long runs of PEX, and the need for oxygen barrier, for a...

[nyoo65]

...heating engineer or plumber.? Is there a plumber, or heating engineer, who might answer a question from a novice? I want to add a loop to 1/2" pipe that runs from the mains (town supply) to my hot water heater. That runs is currently about 5'. The new loop will go out to my back yard, through a solar heat store, and come back to the standard (hardware superstore) electric hot water heater.

Question #1: The designer of the solar thermal structure advised me to use PEX because my water is 85 psi, but many PEX vendors sell a costly "oxygen barrier" PEX if my system has any ferrous parts. I'd prefer to use the cheaper commoner PEX. How do I know if I have any ferrous parts?

Question #2: This new extra loop will add 160' of 1/2" copper inside, and 1/2" PEX outside (80' going, 80' coming back) buried below the frost line, and 200' of 1" PEX inside the solar thermal unit. That's 360' overall. Will 360' reduce pressure to the upstairs shower and sink?

Alt. for the 1" PEX is 60' of 3/4" copper.

Thx.

[rancidcrab]

Well, I'll defer the pressure question to a plumber, but I'll bet itl will be considerable. A boost station might be called for.

I'll try on the oxygen barrier question though.

PEX is good stuff. If the UK is like the US, the major differences between brands will be the fittings and manner the seal is made mechanicaly. The pipe itself will be pretty much equal.

Oxygen barrier PEX simply means it resists intrusion of oxygen into the pipe. A totally unnecessary requirement on an "open" system.

Oxygen barrier is advised on "closed" systems (e.g. a heating system), particularly on in-floor radiant systems where air can create havoc in the long loops of slow moving water.

If the fluid in the line is "open", then forgo the oxygen barrier PEX... unless your dealer can come up with a compelling argument for its necessity in your application.