tundish location for condensate drain

[wozzzzza]

saw this on youtube the other day, confused the crapout of me.
if you look at the one with the green tick, im thinking what is stopping the water going up and out into the cupboard there is the sinks are full and you let them out quick?
if that is a one way system there at the tundish, what happens if it deteriorates and fails? floods the cupboard?

[droog]

if you look at the one with the green tick, im thinking what is stopping the water going up and out into the cupboard there is the sinks are full and you let them out quick?

If that happens then there are problems with your drains that need to be fixed.
The design cannot compensate for every single problem that may happen.

[rambunctious]

saw this on youtube the other day, confused the crapout of me.
if you look at the one with the green tick, im thinking what is stopping the water going up and out into the cupboard there is the sinks are full and you let them out quick?
if that is a one way system there at the tundish, what happens if it deteriorates and fails? floods the cupboard?

Yep not good.
Best practice is for the tundish/open drain as high as possible under the benchtop.
But of course as above, that will not compensate for blockages in the system.