Just insulating the beer line is not enough...it needs to be cooled too. Shorter runs (10 feet or less) can be "air cooled" using a blower mounted in the fridge. Anything longer and you need to use a much more expensive, commercial-type chilled glycol system.
The object with both systems is to keep the beer line as close to the temp of the beer in the keg ALL the way to the faucet (tap). Once the beer becomes warmer than it is in the keg, you will get foam and lots of it.
Another thing to consider is the amount of resistance that 25-30 feet of "slack" line creates. Most keg beers require 12-16 PSI of pressure to keep the beer properly carbonated. In your case, if you're running the typical 3/16" beer line, you need A LOT more pressure to push the beer that far - probably more like 30 PSI and that will cause the beer to become over-carbonated very quickly.
As you can see, there's a lot more to having beer on tap than just hooking everything up. There's definitely some science involved and there's not many ways to cheat!
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