Rebending old hepex ?

Dave Carpentier · September 28

25yr old Wirsbo hePex existed beside an oil boiler, circulated ~90f water.

Im at the point of my tear-out where I cut the tubes and remove the remaining iron pipe and CI boiler (got the two 1" unions at the boiler loosened, surprisingly).

Next step would be to reroute the hePex a bit nicer to see where the new Uponor manifold could possibly sit. My existing supply manifold is the higher one, but Uponor suggests (and the new one comes pre-assembled as) supply manifold as the lower rack. The thinking is, if something leaks, the zone actuators wont get dripped on.

I stand a better chance at mounting my new manifold higher if I ignore that suggestion. If I was worried, I suppose I could fab a little roof for them.

The bigger question is… what are the thoughts on rebending hePex that has been sitting for 25 years ? Does it get brittle ? When I cut the tubes and remove all the clamps, Im not even sure if they'll straighten out like a spring or stay in the same shape.

At the least, I would like to use those aluminum bend guides for the upturn below the manifold just to keep it a bit nice ? The new manifold places supply and return fairly close to each other, so I should have enough room to attach all to wall, turn left, and then turn up, instead of the cross-behind as is now. A few of them might have to go straight up, if the manifold ends up about where the in-floor circ is now.

hot_rod · September 28

I don't know about that brand, but we see Caleffi manifolds mounted vertically. That might clean up and shorten those loop ends.

You can also space one out on 2x4 blocks so pex crosses behind one, getting them at the same plane.

I've also seen manifolds flat mounted against floor joists.

UV is what turns pex brittle.

Screenshot 2026-09-28 at 12.29.35 PM.png

Dave Carpentier · September 28

An Uponor manifold is shown in the recent thread about Flow Anomaly. OP has a 4 port plus a 2 port, whereas mine is 7.

I hadnt considered vertical mount. Maybe a long sweep into a vertical manifold ? I think I'd rather stay conventionally horizontal, but maybe the pipes will be happier like that, so I'll keep it in mind.

hot_rod · September 28

If the tube cracks from being brittle, you have bigger problems than manifold position :(

Sunlight or long exposure to low grade UV from fluorescent lighting can degrade the tube.

Dave Carpentier · October 16

Heat gun at about 4/10 and only warmed it up enough to become compliant seemed to do the trick. I didnt want to bend the pipes close to the floor end , so the rack ended up higher than I would have liked.

Fingers crossed when I pressure test it (water) this weekend. Im definitely going to put a curtain or such on the east facing window in that room, now that the pipes will be fully exposed to some amount of sun.

Here's the rest of the in-floor board layout. Good idea to put another vent on this side ? The two currently planned vents are on top of the buffer tank and a high point vent on the air handler pipes.

Adding: The pipes look like theyre all wrinkly in this pic. I downsized it to send sms to someone. Funny to think someone might see this and think I melted the fk out of them and just terminated it. lol

EdTheHeaterMan · October 16

I remember when the Wirsbo sales rep came to demonstrate the features and benefits of hePEX tubing. He deliberately put a kink in the tubing and then applied a heat gun until the tubing became crystal clear. The kink disappeared, and the tubing returned to its original shape, perfectly round again.

At that point, the tubing was so hot that you couldn't handle it without thick gloves.

If you wanted to put a bend in the tubing, you could form the bend while the tubing was still translucent, then hold it in that position until it cooled to room temperature. Once cooled, the tubing would retain that bend.

I would take a piece of that old tubing and allow the tubing to go translucent to see if it will go back to it's original state as it cools off. I think it will and perhaps take some if not all of the brittle away. Then you can do the rest of it, that you want to keep in place

Dave Carpentier · October 16

After 25yrs , the insides of those tubes had a dark layer. Before I tore the old piping out, I did run some Fernox cleaner thru and soaked , which did rinse out quite black , but I think there's a fine caked or dyed layer in it now. I remembered about stop heating when it goes clear, but I wasnt going to see clear anyhow lol.

I could still hold the heated section with bare hands to bend. It was hot but not ouch-hot.

Rebending old hepex ?

Comments

Categories