The spunding valve is attached to the gas post on the keg. You could daisy-chain kegs. The last in the chain gets the spunding valve.
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Not to derail the thread too much, but
Can you explain how purging and sanitizing multiple daisy chained kegs works in practice?
I understand the gas out from the FV goes to the gas in on the first keg, which is filled with sanitiser and operates exactly like a normal keg - the CO2 from the fermenter pushes the sanitiser up the liquid dip tube and out of the liquid post, thus purging and sanitizing keg 1.
But where is the liquid out connected to on the next keg?
It can't be the liquid post as this would leave no way for the sanitiser to escape into the following keg?
But if you connect it to the gas in, then how would the air inside keg 2 be able to escape to make room for the starsan?
As soon as there is enough starsan in keg 2 to cover the bottom of the liquid dip tube, surely either:
A) the O2 contaminated air would have nowhere to go and cause a blockage which would prevent the sanitiser from moving any further forward
Or
B) when the pressure inside keg2 got high enough, starsan would be forced up the liquid dip tube without displacing the O2 rich air trapped in keg 2 - and therefore neither purging nor sanitizing the keg.
Being able to symultaneously purge and sanitize all my kegs with FV gas ready for closed transfers would be a god send ... But I just can't get my head around how it would work for more than one keg at a time.
I guess you could pull the prv on keg2 till sanitiser comes out, then close it and repeat for subsequent kegs ... But I'm guessing this would lead to excess sanitiser in your beer ... And also obviate the need for the sounding valve in the first place ?