Kitchen Extractor ducting

[kevt296]

Hi All
Sorry if this has been raised many times already but I couldn't seem to find exact info I am seeking.

Already have kitchen extractor fitted, purchased from B&Q several years ago. It has been used in re-circ mode and I want to fit external ducting. It is fitted to an outside wall.

Outlet from extractor is 121mm dia which seems an odd size as I am only finding 100, 125 & 150mm commonly. Is this smaller to accommodate tape or sealant etc?

My thoughts are to fit 125 - 100mm reducer, short length of 100mm dia pipe, connect to rectangular cross section adapter (due to limitations of ht above extractor), rectangular cross sectional pipe through wall and then external vent.

Could you tell me how to join these, pvc cement, sealant or tape and should I use sealant between pipework and brickwork or is there something else recommended?

Any other tips?

Apologies if this all seems a little basic. I would consider myself a reasonably competent DIY'er but always like to get a little instruction, particularly when drilling through a main wall!!

Thanks in advance for any help (I hope!!)

 

[theprinceofdarkness]

I think you are over complicating things, its only dirty air. Only use silicone goo or nothing to hold the sections together or you might find that the fan (or something) cannot be removed for cleaning/replacing without breaking it. The way I would go about thing are :- First drill a horizontal hole straight through the wall, this is your reference, mark out and drill a series for holes in the inner skin just to clear your 121mm diam. Go to the outside mark a hole 1" down from your reference hole, because you want a slight downward tilt to the ducting, drill a circle of holes to fit your outside terminal to. Knock out the holes into a clear round hole. Wrap up a piece of visquerene (Sp.?) or thick plastic DPC material which has the thickness of the wall plus a bit in width and at least 4 times the maximum diameter of your hole in length. Roll the piece up and with a good glob of silicone on both skins of the brickwork, unroll it and it will spring out. It is best if the overlap is at the top of the tube. Carefully cut the excess bits into petals and fold back against surface of the wall. Drill and plug for the fan and outer terminal.
Frank

 

[kevt296]

Wow, thanks for the comprehensive instructions Frank. Really appreciated.