Concern_flex liner securing on 90 deg Elbows

Problems related to residential installations.

Moderator: juster

Post Reply
Regular Contributor
Posts: 14
Joined: Wed Jun 24, 2015 1:48 pm

Concern_flex liner securing on 90 deg Elbows

Post by RunningLow » Tue Jul 21, 2015 7:33 pm

One run of new 8" flex.
It must make a 90 off the plenum start collar & about 70 deg turn into supply boot. Decided to use Elbows at both ends (adjustable).
Meaning, for El at the start collar, the liner goes over El's crimped end.

To get the liner & zip tie past the 1st roll / bead (at El's crimped end), have concerns on stretching it SO much farther - on the El's outside radius VS. the inside radius.

Doesn't that much uneven stretching increase chances - one side of the liner pulling much tighter against the El's sharp edge & get cut? (have pics - can't post).

On El's INSIDE radius, I don't see how tape is applied smoothly or get a good seal. Where the liner stops, the El immediately turns 90 deg.

IF... getting the liner & tie past the adjustable El's bead (all the way around) is * highly recommended,*
on the El's OUTside radius, the liner must stretch 4.5" - from end of pipe, to a bit past the bead (sliding joint).
On INside radius, liner can only slide onto the El ~ 1.75" - max. The El's bend stops it from going farther.

ALSO, on adjustable Els (set to 90) if the zip tie is against the sliding joint (bead) - all the way around, it makes the tie longer. It is "SLANTED" around the pipe - not perpendicular to that section's longitudinal center line.
Like tying a safety rope around your waist. Only, in the front, the rope's around your chest; in the back, it's waist height. It's no mystery why the rope then slides off.
? Placing the zip tie at a slant around a pipe - couldn't metal expansion / contraction could cause it to loosen over time?

Same issues on the smooth end of an adjustable El, except that end has longer section of smooth pipe, before reaching the 1st bead (joint). Not sure on the El's smooth end, if it's mandatory to get the liner & tie past the bead?

Post Reply