You know its funny. Ive used that calculator to determine one of my hose lengths at 4 feet, and I just randomly tried a 7 foot one and have noticed no difference. But I will say, Im thinking the brewers friend one may be wrong cuz I just went out and tried a few more calculators and got closer to 10 feet
The Brewer's Friend calculator is not wrong. It's just giving you the minimum to meet the resistance for pouring flow per the math and accepted flow rate:
I hate all of the misleading information on the web regarding "balancing" draft beer systems. The vast majority of it completely ignores basic laws of fluid mechanics and makes assumptions that often don't apply to homebrewers and home-draft users. The first misconception might stem from the phrase "line balancing". This implies that there's some magic balance between pressure and resistance that results in a good pour, and anything else will cause foam. This couldn't be further from the truth.
The reason resistance is required in a draft system is to slow the flow of beer down until it's gentle enough that the CO2 doesn't get knocked out of solution and result in a ton of foam as it makes it from the faucet to the glass. How slow and gentle the pour needs to be to accomplish this is highly dependent on the serving temperature and carbonation level of the beer. The warmer or more highly carbed the beer is, the slower and gentler the pour needs to be.
For commercial systems where the beer is stored between 33° and 36°F and the carbonation level is between 2.5 and 2.7 vol, people have found that the fastest a beer can be poured without excessive foam is ~1 gal/min. All of the equations, resistance figures, calculators, and most of the articles you've likely found assume this flow rate. There are a couple problems with this assumption. First, if you use those equations and resistance figures you'll end up with a flow rate of 1 gal/min, which in many cases is too fast and will result in a firehose of foam. The second is that line resistance is not a constant for a given type of beer line, it's dependent on the flow rate. This means that those figures and equations are completely useless for any flow rate other than 1 gal/min.
The other common misconception is that extra long lines, or additional resistance beyond the "ideal" or "balanced" figures will cause some sort of problems or foaming. There are only two side effects of extra long lines, a very slightly slower pour, and the ability to serve beer at a much wider variety of temperatures and carb levels without any issues. Since line resistance decreases exponentially as flow rate decreases, doubling your beer line length barely has a noticeable impact on how long it takes to fill a pint.
Most of what I've typed above is more applicable to traditional permanent serving systems. Getting enough resistance in those cases is imperative, as the serving pressure can't be changed without affecting the carbonation levels.
The calculators and such can be a very useful tool, but you have to know it's inherent limitations. If you like to keep your beer really cold and at moderate carb levels no matter what, then go ahead and use it. Just realize that the "ideal" and "balanced" result it gives you is the fastest a beer under those conditions can be poured without excessive foam (very important to a bar selling beer to pay the bills, but not a worry for me).
That's why I always add a few feet to those calculator results. To see this verified, add a 30 foot line to your 11psi keg, and it'll pour a beer just fine. It might take 5 seconds longer to fill a pint than a 10' line, but that's all.
