Sorry if I expressed myself not clearly - when my pump is turned off, wort is flowing down the recirculation pipe due to gravity instead of up. It’s not a big amount of liquid going into the other direction, just enough to free up a clogged pump often enough. Also, this happens during the mash, not the sparge.
I absolutely agree that going for perfection is a recipe for unhappiness. It’s only that I’d like to remotely get into the ball park of a recipe. At the moment, I’m so far off that I wouldn’t even dare to try Belgian beers, strong stouts/porters or anything like that, just because I wouldn’t know how to fit enough grain in my mash tun should I try to correct for the low efficiency.
That said: As I also like coffee, I’m aware of how challenging works. I believe I stirred seriously, but you never know. Other than that my recirculation was not continuous, instead I set the pump to 60% - which turns it off 40% of the time, allowing for some backwards flow to happen. This is often enough to free the pump if it’s blocked, so I hoped it would help agitate the grain bed in a way that prevents channels from forming. Again, you never know.
If anybody reading this who also uses an AIO-system like BrewZilla, Grainfather and such and might care to share photos of their grain crush, that might also help me.
Oh yes, I totally forgot to mention that: 19 litres of strike water, 10 litres of sparge water, warm/hot-ish.
71 °C is the temperature that will drop down to 67 when adding the room temperature grains, yes. The grains are also fresh, I bought them only a couple of months ago and stored them in air tight buckets with click- or screw on-lids ever since.
I know about the purpose of a step mash and my last two brew days involved them, yet without benefit. What I picked though up is that given today’s grains, starting the mash as low as 50 might even be detrimental to the head retention as the proteases might eat away more protein than required. But on this, I’m only reciting theory learned elsewhere and can’t speak from experience.