Advice on dodgy cooker hood extraction installation

Joined
10 Dec 2025
Messages
1
Reaction score
0
Country
United Kingdom
Hi folks, first post here. Recently had an electrician install an extractor for our cooker hood. I requested the core drilling and extraction ducting be 125mm which is specified by Baumatic. No problem they said…

Day of the install the guy keeps moaning about how 100mm ducting is standard and 125mm is a pain for various reasons. Then says he brought a 100mm kit and will have to run to Screwfix for the 125mm. He leaves and core cutting guys come and cut a hole big enough for 125mm.

Guy comes back with not a 125mm ducting kit but a 5’ long plastic pipe with a 90 degree bend at one end. This seems weird but he claims it’s all they had. He cuts it to size and finishes the install while I look after my son.

The last thing is installing the vent grille/cover on the outside of the house. Rather than use the included screw kit, the guy just puts a bunch of white sealant on the edges and sticks it to the exterior wall. Mind you it’s raining and around 4 degrees out, seems like a bodge but he claims it’s fine.

Fast forward 3 weeks and the extraction doesn’t seem to be doing much. We’ve had an air quality monitor setup since my son was born to check PM 2.5 and VOCs, and we’re not seeing much of a reduction compared to when the hood was only recirculating. So I take off the hood cover to see how the ducting is connected and find that there are 3 unsealed junctions which are bleeding air. This is because the plastic pipe is actually 130mm and is just sitting over the 125mm Baumatic vent outlet pipe attachment (black thing at the bottom in the photos between metal hood and plastic extraction pipe) with no clamp or sealant.

I put some duct tape around the 3 junctions and will monitor the air quality over the next few days but basically this whole job seems like a total bodge. I’m wondering if it’s common or even safe to use plastic piping instead of the standard aluminum ducting, and if the external vent cover is going to fall off or let rain in.
 

Attachments

  • IMG_8052.jpeg
    IMG_8052.jpeg
    380.9 KB · Views: 20
  • IMG_8053.jpeg
    IMG_8053.jpeg
    168.8 KB · Views: 21
  • IMG_8054.jpeg
    IMG_8054.jpeg
    376.2 KB · Views: 21
the plastic pipe is actually 130mm and is just sitting over the 125mm
Where are you measuring this? 125mm inside diameter is very likely to be 130mm outside diameter.
BTW I did exactly this job myself but I stitch-drilled it as I couldn't really justify acquiring a 125mm drill.
 
If that is your total distance then that very short run should be very powerful and make a massive difference in the kitchen. The gaps you have taped up would not effect the flow much. Can you feel it outside, what grill is outside.
 
Guy comes back with not a 125mm ducting kit but a 5’ long plastic pipe with a 90 degree bend at one end. This seems weird but he claims it’s all they had. He cuts it to size and finishes the install while I look after my son.

Tight 90degree bends, will drastically reduce the flow, but at least they have used rigid pipe.

The last thing is installing the vent grille/cover on the outside of the house. Rather than use the included screw kit, the guy just puts a bunch of white sealant on the edges and sticks it to the exterior wall. Mind you it’s raining and around 4 degrees out, seems like a bodge but he claims it’s fine.

That depends on the 'sealant' used. Hopefully, the grill, is fitted with some sort of automatic opening mechanism, to prevent wind blowing in?
 
Looking at the very short distance you could have almost got away with just a slow bend like this and straight out.
https://www.i-sells.co.uk/product/g...l9PSdf4KVd59ej9iZupzsQwbRyZtfTxhoC9M0QAvD_BwE

I saw a guide somewhere that said you take the hood manufactures recommended max duct run - say its 5m then for every 90 bend you then take off 1m
The OP doesn’t really even have a run so it should be amazing, odd as to why not
 
We haven't seen a photo of the outside grill yet, depending on design, they can add a lot of back pressure.
I have the one with 3 flaps but on studifying it I could see that under operation one flap was catching so I did a bit of trimming with a Stanly knife so it fully opens now..
 
I would prefer plastic pipe. Def check all is sealed up ok. If so, you may have a faulty cooker hood...
 
My friends cooker hood is powerful the local glider club use it to launch their gliders!!!
 
I have the one with 3 flaps but on studifying it I could see that under operation one flap was catching so I did a bit of trimming with a Stanly knife so it fully opens now..

Ours, is a single flap, with the pivot off-set, so gravity closes it, and wind blowing on the faces, closes it even tighter.
 

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Back
Top