My endoscope inspection showed up significant build up of dust in the bathroom extract ductwork (and to a lesser extent in the ensuite extract). The kitchen extract has a filter which stops the dust but allowed grease to clog up the extract fan in the unit (and may well have been why the fan failed).
The industry doesn’t seem to be set up for domestic ventilation cleaning, so I decided to give it a go myself. I discounted the systems where you have to screw multiple sections of rod together and opted for a Wohler Mini Viper S which has a thin flexible rod housed on a roll, and a 70mm ‘PEK’ brush (to suit the 63mm ID of my ducting).
You have to be quite rough with the brush, and push and pull it through the duct run several times, (so it would be best to avoid joints if possible) but afterwards the ducts look as good as new.
I rigged up my vacuum cleaner with a connector made from online ventilation parts (with double gaskets to provide an airtight connection to the plenum box in the ceiling) which worked perfectly and no mess!
For my system, the amount of dust build up in the ducts is very definitely affected by the dust filter, or lack of one, to the room terminals. There is far less dust build up to the ensuite extract where I fitted a filter than to the bathroom. It would seem sensible to fit the filter to extend the duct cleaning maintenance interval, but the downside is the filters at the terminals need vacuuming monthly, which few users would tolerate, so practically probably best to leave the filters off and then accept the need to clean the ducts regularly, in my case every 3 years.
Interestingly, the noise level at the bathroom terminal has definitely dropped now that it is no longer clogged with dust and this does beg the question why the system wasn’t specified with 90mm OD ducting rather than the 75mm to lower noise and extend the maintenance interval.
The total cost of the parts was around £250 (and quite a few hours research), but now I’m set up the cleaning is fairly quick, and I suspect this may have already paid for itself or will have done so after the next clean in 3 years’ time.
Overall, after a far bit of research and set up, the cleaning was easy, but it does suggest that the domestic ventilation industry, from designers through to installers must ensure that a cleaning strategy is implemented throughout. Without cleaning my system would likely have been unusable within around 10 years and had I not designed in cleaning, would have caused a real problem.
