125mm MeV ducting system best jointing methods

[sparkyork]

Hi all
started work subbin for a new company and currently on a new build.

mev system going in comprising extract from kitchen and all wet rooms.
125mm round PVC ducting, elbows etc.
all pipes are individual and go to the loft to a common extraction point where they are exhausted through the roof.
got some crackin hours available so want to make sure it's bang on.
I immediately thought solvent weld but the powers that be we're going the silicone the connection points, screw tap it all together and foil tape around the join route.
ive pretty much got it all in and will be doing the final connections tomorrow, question is do I solvent weld it all up and screw and Tape or silicone etc, don't do it everyday so don't know the potential tips n tricks lol

cheeers

 

[LankyWill]

I have done a fair bit of ducting to MEV systems and i would suggest- cement the the joint and then wrap a generous layer of foil tape round to cover it. Screws only make poor connections and will effect fan testing later on.

 

[sparkyork]

Cheers, a previous firm have done a few plots and they had screwed but covered the screws and the joint with foil tape, on a previous job many plot had damage to joints when it all got insulated, they all fell apart! I know what your saying about the screws but they do provide a role I guess, with tale over the top of the screws would that not be pretty good?
If I can get away with not screwing I'm all good, just wanna make sure it's right as it looks like over 100 houses have all been screwed this way and many must of passed as three occupied.
Just makes it hard to know what the best long term solution, but then solvent weld drainage pipe works so yeah why the screws lol

 

[sparkyork]

Just been on vent axis mev site and there instructions state mechanically fixed and silicone sealed and taped. No mention of glue which I do find a little strange but there must be a reason?

 

[JulianC]

Normal to use a flexible low mod silicone or acrylic sealant to maintain some flexibility and take up any misalignment (or indeed gaps between fittings from different manufacturing tolerances). Then tape or self tapper or both according to personal preference/manufacturer instructions etc. This also allows for joint dismantling for the cleaning of ducts (which in a domestic, let's face it, is never gonna happen). If you're happy that the duct won't be subject to movement and cleaning, don't see any reason why it can't be glued.

 

[sparkyork]

Cheers,a colleague advised me today that we're doing as per manufacturer which is siliconed, and taped. No screws required either. Wish I'd of siliconed it up yesterday but was prob wise to wait for the definitive method!
Cheeers