[s002wjh]

is it ok to connect a 6" flex/semi-rigid and rigid takeoff together? i have some obstacle that require a U-turn (not a tight turn), so i like to hook up some flex to rigid one for the turn. also for connection between the two, do i just foil type together or there are more permanent ways to do it.

update w/pic: the concrete wall on the left is the obstacle which block 3-5 inches of 6" pipe if i use rigid takeoff and elbow. try to figure out the best way move the pipe on right to the left

 

[yuri]

is it ok to connect a 6" flex/semi-rigid and rigid takeoff together? i have some obstacle that require a U-turn (not a tight turn), so i like to hook up some flex to rigid one for the turn. also for connection between the two, do i just foil type together or there are more permanent ways to do it.

Post a pic of it.

Flex will reduce your air flow a lot more than smooth pipe. You can get 6" galvanized or aluminum elbows usually at HDepot and I would use them. Flex should work but smooth pipe is better.

 

[icerabbit]

If possible, ideally, you'd do it with a pair of metal adjustable elbows, if need be with an extra section of rigid pipe. Add pipe strapping to support, where needed.

( I just had to redo a lot of flex pipe in my house, due to improper strapping ... older work for the previous owner by the biggest HVAC /+ Plumbing company in town ... I used two three times as many actual plastic straps versus metal duct hangers and wire rope and ... )

Any DIY big box store or decent hardware store should have some adjustable HVAC elbows.

 

[s002wjh]

Post a pic of it.

Flex will reduce your air flow a lot more than smooth pipe. You can get 6" galvanized or aluminum elbows usually at HDepot and I would use them. Flex should work but smooth pipe is better.

k just updated with pics. if use elbow, seem there gonna be alot 90 degree turn instead a large radius flex turn.

 

[roughneck]

Is that 6”? Looks bigger.
If you do flex you’ll have to step up a size to maintain airflow.
The column in your photo could easily be worked around with rigid duct.

 

[s002wjh]

Is that 6”? Looks bigger.
If you do flex you’ll have to step up a size to maintain airflow.
The column in your photo could easily be worked around with rigid duct.

ill double check when i get home, but i remember i measure it as 6". how would i work around the column with rigid? rigid seem require multiple elbows

 

[roughneck]

It would require 4 elbows. These would be constant diameter and not cause the turbulence flex would.

 

[s002wjh]

thats quite a bit elbow wouldn't it be better use a flex since the radius of the curve gonna be larger than twist and turn of elbow.
guess the other option is extend the square duct by 4', but i think those require pro to do it?

 

[roughneck]

It’s never better to use flex.
Its an airflow killer.

 

[yuri]

I would use the metal elbows. Look inside a flex duct and and at the ribs/corrugations and they kill airflow like Velcro is sticky. You are at the end of your duct so you have real good air pressure there and will get good flow anyway. If you can use them as 45 deg elbows as they are adjustable that is better. I cannot tell if you have enough room for that. 45's have less resistance.

 

[s002wjh]

i only saw some 90 degree elbow, is there 45 degree elbow takeoff?

 

[roughneck]

i only saw some 90 degree elbow, is there 45 degree elbow takeoff?

The elbows are adjustable.

 

[s002wjh]

The elbows are adjustable.

i've seen some 45 degree at the takeoff end, which seem to have lower profile than the 90 degree elbow. something like this

https://www.lowes.com/pd/IMPERIAL-6-in-x-7-in-Galvanized-Steel-Adjustable-Duct-Take-Off/1000237101?cm_mmc=shp-_-c-_-prd-_-plb-_-ggl-_-LIA_PLB_171_Air-Circulation-_-1000237101-_-local-_-0-_-0&ds_rl=1286981&gclid=EAIaIQobChMI1P2uxeTl_AIV5RTUAR1hewo5EAQYASABEgIZkfD_BwE&gclsrc=aw.ds

 

[yuri]

That would work. They are all adjustable but some are sticky and tight and you have to rap them with the handle of a screwdriver to loosen them.

 

[icerabbit]

Seeing what we see now. I'd probably flex that, rather than zig zagging with elbows. I'd certainly not do a sharp 90 3x.

From the picture it looks like you should have enough space for one elbow at the trunk, come forward past the pillar and then use two elbows to make an offset 45 slant, as needed.

Alternatively, you could possibly come right out the square end, add a damper for if balancing were required due to installing on the very end, (I'm not an HVAC guy) elbow 45 degrees till past the pillar, then 45 from behind the pillar. That would impede the airflow the least.

Another option would be to ask a metal fabrication shop, to fabricate you a solution. Round to rectangular that you can strap to the pillar or hang from the ceiling, come around the pillar, then back to round. I have had to get a few things custom made in the past. Just measure and draw it up. Probably not required for your situation, but it is a professional option.

 

[Heating Solutions]

Don’t use wireflex if you have enough craftsmanship to install rigid steel ducting. You don’t need four 90 degree turns, just four 90 degree adjustable elbows bent to 45 degrees or so and your airflow will be way better than using wireflex duct.

 

[s002wjh]

thanks, i forgot those 90 degree can be adjustable, so maybe ill try play around with that, see if i can get a shape like below with 4 90s

 

[Heating Solutions]

Can’t tell you for sure how things will go without being there but for sure using adjustable metal elbows and rigid steel ducting vs. wireflex will be the best option.

 

[Dwellonroof]

Could you just dogleg a couple short pipes?