I have an apple cider than when the serving pressure is at 20 psi, it doesn't foam much (pours as expected), but when I set it down to 8-12 psi, it massively foams. It was fully carbonated at 20psi (in keggerator on 20psi pressure for about 3 days, then initially lowered); I'm wondering if I'm doing something wrong or why it's foaming so much. The keggerator is kept between 36 and 38 F, and I'm considering secondary regulators to help with this problem so that I can adjust per-tap. I'm serving with Perlick 650SS faucets; doesn't seem to matter what the flow control is set at.

Here's my theory: Carbonated to 20 PSI, it has a certain amount of CO2 in it. Pour it, the CO2 just starts to come out of solution, so it doesn't foam much. But, lower it to 10 PSI, as it hits the tap line it already starts to come out of solution, by the time it hits the tap itself it's partly foam already, so when it hits the glass it's inclined to foam even more. In other words, at high pressure, there are no (few) nucleation sites to initiate the foaming, while at lower pressure immediately after high pressure, the nucleation sites (tiny bubbles) are plentiful. Of course, I could be completely wrong here (I often am) but it's a guess. Leave it at 10 PSI for a couple days, see if that changes.

I'll see. I didn't think leaving at the charging pressure for an extended period would be a problem. I'll report back in a few days while it rests at ~10psi

Release some pressure from the keg to drop it just under 10 psi - you'll hear the headspace start to refill. Then let it rest a few minutes to an hour and try pouring again. Once the two equalize it shouldn't foam all that much.

I've now done that today, I'll check a pour tomorrow, but I made sure it did drop pressure and refill some headspace in both kegs (maybe I forgot to do it in both and did just one... dunno, but now both are done)

I'd say it's mainly just the imbalances of pressure. Degassing the keg a few times and then resetting to your serving pressure should help, but it may take a day or 2 for it to balance out. Other things to consider are length of serving line, line ID and temperature balance throughout the serving line. Also, make sure as you pour not to try to restrict the faucet. Fully open, fully closed. Cheers

Ok, so now I have essentially the same problem: no matter how low I make the pressure in the keg I still get mostly foam. The photo below is an example: carbonated to 12 psi at 35F, pressure released completely from the keg, then increased just enough to get some flow from the picnic tap. Maybe 4 psi? After about 30 seconds the 60 oz. pitcher looked like this. Admittedly, this recipe (a Basement IPA tribute) has a wonderfully pillowy head that lasts and lasts... but give me a break, I can't get a full glass! I truly believe all the components to be clean.

@Trialben yes, I learned early on that picnic taps require full throttle all the time. @Sunfire96 the whole assembly is in a fridge, keg, tap & line, and probe. I find that even a gentle pour from the pitcher is about 1/3 (or more) foam.

just went through This. besides Temp and pressure is Line resistance. how Long is your beer line and what diameter?

@Minbari it is a standard picnic tap assembly, so maybe 48" long of 1/4" or 5/16"? @The Brew Mentor OK will try that later today. (5:30 am is too early for a beer...)

Even with a party tap, you should still have a minimum of 5' of 1/4" beer line. The heavy wall restricted type.

If it is 1/4" ID. It wouldn't be enough. I only had 3 ft of 3/16 in my system. Doubled it to 6 and the problem went away

i have to run 10-12 feet of beer line, but I live at elevation. A few years ago my neighbor set up a tap, and would not believe me that length is important. I serve at about 34-36F and run about 10-12 psi

If its a wheat beer, that will contribute to high foam. At least that is the what's happening with mine right now. I have completely disconnected the gas, pulled the release valve, let it sit and I still get half foam. If you can figure it out, let me know.

Stolen from another site...... At the tap end of our balanced keg system we want a slight positive pressure to push the beer out, but not enough to foam. Generally this would be between less than 1 psi. So let’s target a tap end pressure of 1 psi. The math from here is pretty easy to calculate the balanced line length (L): L = (keg_pressure – 1 psi) / Resistance So starting with our example of 12 psi keg pressure, and some typical 3/16″ vinyl keg tubing (which loses 3 lb/ft) we get L= (12-1)/3 which is 3.66 feet. So a 12 psi kegging system would provide 1 psi of pressure at the tap with 3.66 feet of tubing. Note that some authors leave out the 1 psi tap pressure (i.e. use zero tap pressure) and simplify the equation to L= (keg_pressure/Resistance) which makes the math even easier (the simplified equation would give you 4 feet of tubing vs 3.66 ft). The truth is that you can target anywhere between zero and 1 psi at the tap and still be in balance – the difference is relatively small, though a slight positive keg pressure will give you a better flow rate. The four foot example with 3/16″ ID vinyl is great if we only have a few feet to go (i.e. in a fridge) but what if one needs to go further? A simple switch to 1/4″ ID vinyl tubing will get us there – looking at the same 12 psi keg system we get: L = (12-1)/0.85 = 12.9 feet. So with the larger tubing we can deliver our beer to just under 13 feet. For other applications we can consider polyethylene or stainless. However if going a long distance one needs to also consider refrigeration – as you don’t want a large volume of warm beer in the lines. Beer Line Length and Elevation Changes in elevation also come into play if you design a more complex serving system. The rule of thumb is that your beer loses 0.5 psi/foot of elevation gain. So if your tap is 1 foot higher than the keg it loses 0.5 psi, and conversely if it is lower than the keg it will gain 0.5 psi per foot of elevation. So if we roll this into our equation, we get the following for a given height (Height – in feet) of the tap above the keg itself: L = (keg_pressure – 1 – (Height/2)) / Resistance So lets go back to our original example of a 12 psi keg pressure, 3/16″ ID vinyl tubing and this time put the tap 2 feet above the keg itself. We get L=(12-1-(2/2))/3 which is 10/3 or a line length of 3.33 feet.