# Forum Home Renovation Plumbing  Which Pipe for rangehood exhaust

## jimbo_jones

Hi all,
I need to vent a new rangehood to the outside world. The rangehood says to use metal or high temp PVC pipe for the flue.
I can't find out temp details on the standard DVW or stormwater pipes. 
They both seem to be made from UPVC.
I need 150mm (ideally) or 125mm - which sort of pipe should I use? 
Thanks,
Jim

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## Gooner

Jimbo, they sell rangehood venting kits at Bunnings. Around $130 when I bought mine.

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## Pulse

I just used 100mm DWV PVC, unless you have a high temp gas commercial kitchen, how hot are the odours from your curries really? 
Pulse

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## GeoffW1

Hi, 
It is best to use fire rated metal ducting such as the stuff here  http://www.dougsmithspares.com.au/fi...-O%20FLYER.pdf 
Cheers

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## Pulse

Why fire rated, seriously who sucks flames up their domestic rangehood. I can hold my hand 15cm above the frying pan, so 600mm above range, once mixed with surrounding air the temperature might be 10 degrees above ambient in the exhaust. I think in practical terms do what is cheap.  
Pulse

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## rrobor

Doesnt have to be fire rated, but problem is a ducting kit can bend to where you want it and it expands and contracts to length. Murphies law states that your PVC pipe whacks into a rafter or other such thing.

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## jimbo_jones

Thanks for all of the replies.
I need to take it up out out of the skillion roof, probably through a Dektite, so I didn't think about the flexi stuff because I would still need a rigid pipe up through the roof. 
Geoff - thanks for the link - I think I'll go visit Mr Smith - he seems to be the man! 
Thanks again,
Jim

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## tricky4000

Use the flex aluminium piping and stick a china hat on top.

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## GraemeCook

> Why fire rated, seriously who sucks flames up their domestic rangehood. I can hold my hand 15cm above the frying pan, so 600mm above range, once mixed with surrounding air the temperature might be 10 degrees above ambient in the exhaust. I think in practical terms do what is cheap.

  
If the hot oil in your frying pan catches fire, Pulse, how do you keep the flames out of the range hood and ducting? 
ABS statistics report 1,700 kitchen fires a year in NSW alone, and over 20% of these are in flues and range hoods.   Australia-wide this extrapolates to over 500 flue fires a year. 
Secondly, have a look as to how detailed and specific are the rules governing ducting in commercial kitchens - I know, there's a lot more heat - but they do not create such rules and enforce them so actively if there is no real risk. 
Cheers 
Graeme

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## wonderplumb

I use 4" pvc usually to get through the roof with a chinamans hat on top. A lot of the guts of rangehoods are plastic anyhow these days.

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## wonderplumb

I use 4" pvc usually to get through the roof with a chinamans hat on top. A lot of the guts of rangehoods are plastic anyhow these days.
If you worried stick a fire collar around it! :Biggrin:  :Eek:  :Biggrin:  :Eek:

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## rrobor

If Graeme wants to look back posts you will find we did an extensive look at this before, The result is, if the mesh grills give way then whatever your pipe is made of,the fire in the roof will be a major blaze in a few minutes. Your safety is the grills, so clean them regularly. My advice is never block the pipe, Im not getting back into the physics of that, It sounds a good idea to have a flap which closes when the fan is off. My physics tells me never do that.

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## Pulse

Most cheap slideout rangehoods are plastic as are the fan blades inside them. The only oil fire I saw when my flatmate at uni left the stove on, the flames were about 5cm high and put out by putting the lid on. 
Not saying there is no risk, but that the risks are perhaps overstated and for practical purposes, 100mm PVC is cheap effective ducting.  
Pulse

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## jimbo_jones

Wont using a 100mm duct on a 150mm exhaust outlet make the fan run harder/noisier?

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## Gooner

> Jimbo, they sell rangehood venting kits at Bunnings. Around $130 when I bought mine.

  I still think this is the way to go  :Smilie:  Includes vent, china hat, adapter, brackets, etc.

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