Questions on Filtering

I am looking to add a 2 stage filter to my brewing system for filtering the beer post fermentation. Like the one in this thread. I have a few questions for those that use a system like this.

1. What's the purpose/point of the purge button on the filter housing? There are filter housings that come with or with out this. Any reason to go for one with the purge button vs one with out?

2. I've seen a few setups with these filter housings where people have the filter housing installed upside down. What's the benefit of upside down vs right way up?

3. Gravity vs CO2. I know the setup in the link uses CO2 to push the beer through, but can you use gravity to do this? Ideally I want to use CO2, but that depends on me being able to pressurize the fermentor.

Any advise would be much appreciated.
Cheers
Zac

1. Doesn't serve any purpose for home brewing. Just get what you can.
2. Sometimes you can get a little air pocket, but it doesn't affect the filtering in anyway... so up or down, its your choice.
3. I don't believe it would be possible to gravity feed these. I only single stage filter, but even then I have had to bump up the pressure a bit as the filter starts to clog. My process for filtering is to rack from the fermenter into a keg, then transfer from beer out - through filter - into beer out of the serving keg (fills from bottom that way).

BigB said:

3. I don't believe it would be possible to gravity feed these. I only single stage filter, but even then I have had to bump up the pressure a bit as the filter starts to clog. My process for filtering is to rack from the fermenter into a keg, then transfer from beer out - through filter - into beer out of the serving keg (fills from bottom that way).

Click to expand...

What micron filter are you using and how much beer are you filtering at one time?

Cheers
Zac