Soil pipe (110mm) to 150mm kitchen extractor ducting

[MrsGarner]

Hello all.

This may sound a silly question but how's best to connect 150mm ducting to a 110mm pipe?

Our business have left a small bit of soil pipe sticking out for the kitchen extractor. I was going to reduce the pipe to 100mm ducting but the kitchen surveyor said that it's too small and that it should be 150mm.

I can find reducers for all sizes but not 110 to 150.

I'm thinking get a reducer to use backwards for 150-100mm to use inside the 110pipe and silicone and tape it ok and then use 150mm ducting as normal? Or does that sound silly?

Thanks in advance Louise

 

[foxhole]

You can get a reducer to fit the fan then use flexi foil ducting to your soil pipe. The 100mm ducting will push inside the soil pipe and can be secured with foil tape (heat and moisture resistant).
When you say kitchen surveyor do you mean the guy selling you the kitchen install, if so often untrained and just reading from a script when it comes to knowledge of kitchen install.

 

[MrsGarner]

Do you think 150mm is overkill?

I had bought 100mm ducting and was going to use that for the bathroom extractor and kitchen. He said to my husband (I wasn't there) 100mm is much too small.

I had already found a 110mm-100mm reducer so thought I was all sorted until
He said 150mm required.

We've never had a kitchen fitted before and our last extractor was recirculating. Our current kitchen is in the centre of the house so ideally I wanted the outside extraction.

We just believe what we are told by "experts".... :-/

 

[ironsidebod]

What is the make and model of the extractor? The manufacturers instructions will determine the size of ducting required. They should give acceptable lengths as well e.g it may be ok in 100mm for 1 metre but anything over requires 150mm and so on.

 

[endecotp]

Our current kitchen is in the centre of the house

A long run, especially if it has bends in it, is easier in 150mm.
It is probably still achievable in 100mm but you'll need a powerful fan and you'll need to check the specs carefully. It could be noisy too.

 

[MrsGarner]

Thanks all.

It's a NEFF D49ML54N0B.

I do have a small side issue, which was the main reason for going for 100mm ducting. As the kitchen is in the middle of the house the duct is to run in the ceiling (floor space to the first part of outside wall, I can't really make the hole any bigger tha 100mm rectangular ducting as there is a part of a floor joist in the way (have attached a photo. Though I have no issue to start and finish the duct in 150mm part of it has to be 100mm rectangular to fit through this gap. Easy huh ;-/

 

[Ian H]

I used a 6" to 4" drain reducer on mine.

 

[foxhole]

Had 3.5m of 100mm in my old kitchen for 20 years and no problems.Across ceiling void.

 

[chappers]

but was it working at it's most efficient, the problem is that pressure builds up in the narrower pipe and as endecotp says it then requires a more powerful fan to drive the same volume of air and this resistance can also strain the fan a bit and make it noisy

 

[MrsGarner]

Thank so chappers. I'm happy to run 150mm but at one point I will have to make it smaller to fit through the opening I have so I guess just use maximum 150mm and minimum 100mm. Not ideal as I'd like to have run one continuous length but will just have to make the best of a bad job I guess

 

[vinn]

Reducing from large diameter to smaller diameter is frowned upon.
Where the reducer is inserted is where condensation (or mould) can form.
Condensation might run back down "horizontal" runs.

Flexi-duct is less efficient than solid wall, and will probably collect condensation & mould.

FWIW: there are some very powerful 100mm extractors available.

 

[MrsGarner]

Thanks Vinn,

I am not trying to reduce it per se. The position of the extraction to outside is set. The builders have bricked in a section of soil pipe. So the final outlet is 110mm. There is no way my husband is going to agree to knocking this out of the wall and cutting a bigger hole.

I had banked on reducing to 10m as just assumed that this was the standard (as was on the bathroom fan).

It wasn't until the kitchen surveyor said f needed to be 150mm that I was like b*llocks. But in reality unless I have the duct running across the ceiling it's has to fit in the floor joist space and through the corner of a wall (photo attached). So my only option is 100mm rectangular.

I can start in 150mm reduce to 100mm then go back up to 150mm but that's seems silly. Plus at the end I've got to try and work 150mm back to the 110mm soil pipe....seems like a quandary or not sure if I've missed something really obvious.

I had planned a telescopic extractor so will have a thorough look tonight and see if I can find one nearer to 100mm...

:-/

 

[foxhole]

but was it working at it's most efficient, the problem is that pressure builds up in the narrower pipe and as endecotp says it then requires a more powerful fan to drive the same volume of air and this resistance can also strain the fan a bit and make it noisy

Very little resistance air simply moves faster .