Cold Crashing Woes

[LutzBrauerei]

I've ran into a problem when cold crashing and am looking into how to resolve it.

The problem: As I crash my batch, the vacuum created by the temp change sucks the Star San through my blow off tube and into the fermenter, watering down the batch, and possibly ruining it.

The equipment: converted Sanke Keg fermenter with a Brewer's Hardware American Sanke Fermenter kit w/ Thermowell. https://www.brewershardware.com/American-Sanke-Keg-Fermentor-Kit-with-Thermowell.html

Solutions I've thought may work:

1) Install a flutter/bleeder valve attached inline on the blow-off tube. This would only allow CO2 to flow out of the fermenter and restrict Star San from flowing into the fermenter during cold crashing
Pros: easy to install and relatively cheap
Cons: vacuum pressure inside the
fermenter would introduce
unfiltered air at kegging.

2) Install a tee prior to the blow off tube and install a .5 micron filter in the tee section to act as a pressure relief valve. This would keep the blow off tube from sucking Star San into the fermenter while filtering the air that reaches the batch.
Pros: easy to install and not very
expensive
Cons: Air resting on the batch could
oxidize it.

3) Install a tee prior to the blow off tube and install a gas line in the tee section to equalize the pressure in the fermenter during cold crashing. This would keep the blow off tube from sucking Star San into the fermenter while only introducing FG CO2 into the batch, eliminating oxidation concerns.
Pros: Batches will not have Star San or
unfiltered/filtered air introduced into
the fermenter.
Cons: could be a tricky install to get the
gas line in, a bit more expensive
than other methods.

Has anyone ran across this problem? How did you solve it?

 

[TexasDroughtBrewery]

You are over thinking this...if youre that worried about it use vodka.

 

[oogaboogachiefwalkingdeer]

Must be weak beer if a tablespoon if water is going to water it down. Drink some beer and relax.

 

[GrainToGlass]

I just use an S-type airlock with just enough sanitizer. No problems here.

 

[30_Ounce]

An S bubbler filled properly will not suck in the Star San or Vodka.

 

[MantisTobogganMD]

I've heard of people just coiling up a long length of blow off hose...When you crash the temp you will still suck up StarSan but the StarSan will never make it into the fermenter...if that makes sense. I've never tried it but this would create the closed system you are looking for.