Thread: Vibration from wide-bore air line into BD

I'd been using circa 10mm outside diameter air line to connect my air pump to the 1" bottom drain line via this adapter (right-hand part in the photo): https://www.cotswoldkoi.co.uk/produc...-air-feed-kit/
This was working well, and working quietly, until the rubber boot at the pump end perished.


I replaced it with a wide-bore alternative, a 19mm brass nipple and 19mm inside diameter pipe. The idea was that I suspected airflow as not optimal using the 10mm adapter (too narrow), and wanted a much wider pipe with less friction. In the end the air flow (bubble stream) from the BD does not look any better with this set up than before.


However, this setup gives an audible and tangible vibration. It's not the pump itself, as this had been running near-silently for ages, but when I turn off this airpump the hum vanishes. I'm convinced that this hum is due to the wider bore, and that the vibrations are coming from the air stack and travelling through the concrete base of the pond in which the 1" pipe is fixed. The vibration can be felt touching the walls of the pond, touching a garden chair next to the pond, and can be heard indoors (with concentration). Can't be nice for the fish.


Couple of questions please:
1. Why (what is the 'stiense' behind) this hum generated only with wide pipes? And do you guys experience similar?
2. Am I off the mark to think that a 10mm pipe doesn't give sufficient flow for a BD?


Thanks a lot

Old:
Screenshot 2026-05-19 125926.png

New:
Screenshot 2026-05-19 130741.jpg

Thank you Syd.
I swapped back and the vibration is gone. In fact, the air column rising from the BD looks thicker, denser, now than with the wide pipe, although that could simply be due to a better seal. Either way, my idea that a thick air pipe would deliver significantly more air seems wrong.