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Posts: 2,240
Reply with quote  #1 
This is generally stated as "five to seven times the outside diameter"

So for my 12 mm O/D tube (= 10 mm I/D), I ought to be getting 5 x 12 = 60 mm radius, = a 12-centimeter bend.

(too big for my application)
My supplier states, "84 mm minimum for 12 mm O/D tube - this sounds conservative...
(= a 16-cm bend...)

I experimented using green lentils poured into the PEX tube, and got the PEX very tight, but then it kinked some...

I next experimented with a spare length of three-wire electrical cord pushed into the PER, getting the tightest fit possible, then holding the PEX in a bowl of just-off-the boil water while flexing it.

Going very easy, I got the radius down so that the bend would "go around a Coke Can but with some slack".

A Coke can looks like it is 72 -mm diameter.
Therefore I reckon I get an 80 mm diameter.
Which is over twice the recommendation...

(For my application, I need 9 cms diameter)

So I reckon I am on the lines for what I want...

but just wondering if I am "stretching" the specs any ?

All observations welcome


(1)  "Heat goes from hot to cold, there is no directional bias"
(2) It's wrote, "voilĂ " unless talking musical instruments...


Posts: 720
Reply with quote  #2 
Pex isn't the eaisest stuff to install. The very 1st loop I installed in my crawl space I kinked it in the first 20'. [frown]

I installed the pex myself but it would have been a lot faster & easier with 2 people. I didn't need that tight of a turn, but it's interesting that you managed it.

As for the specs, I would say you are good unless you put a lot of pressure on the line. It may have a problem then.

Central IL
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