Preface
I am writing this to share the mod that I have been using for flow control of my BDB. This mod is a tweak on an old mod. In order to help the reader understand what I mean, I will offer a brief history of flow control mods on this machine.
A Brief History of Flow Control Mods on the BDB
1.) Soon after this machine hit the streets, keen users learned that they could reduce the flow to the puck by opening the water valve. Care was needed in this because if the valve was opened too far, the micro switch was triggered and the extraction was terminated. It was learned that some machines would allow you to open the valve more than other machines due to manufacturing inconsistencies. If you got one with sloppy tolerances, you were a winner!
1.a) It was not long before someone opened the machine and took out the microswitch that was responsible for cutting the shot when the valve was opened too far. This allowed the operator to open the water valve however they liked and the extraction would not be stopped. In both of these mods, the water that was diverted through the water valve, exited the hot water spigot and went to the drip tray resulting in water wastage.
2.) The Slayer Mod. Jake and Peter ( Jake_G & pcrussell50 ) developed the current de rigueur profiling mod. of re routing the tubes so that the hot water valve acts as a throttle, controlling the flow to the puck. In this mod. the OPV acts to dump the excess water back to the tank so that there is no water wastage. A very elegant solution, it provides flow control throughout the shot, wastes no water, costs no money and results in no damage to the machine, making it completely reversible.
Mod 1.b. (the mod I use now).
I pull mostly medium roast coffees and have found that for my taste, the declining pressure profile associated with lever extractions has the most positive impact on the coffee I make. I have had my machine in configurations 1.a and 2 for several months each. Working with the stock Breville hot water valve, I have found it more intuitive to execute the declining pressure profile that I prefer by controlling the flow with the valve as it is operated in Mod 1 and 1.a. In these mods, full pressure is achieved with the valve all the way closed, and to reduce the flow, you crack the valve. In mod. 2. full pressure is achieved with the valve all the way open and to reduce the pressure, the valve has to travel to the point where it is almost closed. I found this harder to control, less intuitive and less repeatable - for me. Mod 2 does offer significant advantages to mods 1 and 1.a if you want fine flow control at the beginning of the shot. Mods 1.b and 2 both have the advantage of not wasting water.
Several months ago, I switched my machine back from mod 2. to mod 1.a. because I found it more intuitive for me to control. However I was frustrated that so much of my good water was going to the drip tray. So I set out to find a way to route the hot water waste back to the tank. After thinking about drilling and melting and all kinds of fabrication tactics I opened up the machine to have a look. I found, as we BDB moders have so many times, that the BDB is almost made with a solution for this mod in mind.
Mod 1.b. How to...
In the deck above the water tank there is a port that leads directly to the tank below. I removed the hot water (tea water) line from the hot water spigot at the spigot. Then secured the end of the hot water line that used to enter the spigot, in the port in the deck above the water tank using a zip tie. I knew I would have to secure this very well or I will end up with water all over the inside of my machine. I also had to ensure that the water line was not inserted so far into the port that I would not be able to remove the water tank. Next, there is a micro switch above the water knob. You have to prevent the switch from engaging with the hot water knob so that opening the water valve does not trip the switch and stop the shot. It's easy. Undo the 2 Phillips head screws that secure the micro switch to the machine chassis. Pull the switch out of its mount and set it further inside the machine, in a place where the switch won't be disturbed. There is plenty of room inside the machine to find a nice place for the switch to live.
Closing Thoughts
I have been running my machine like this for several months. I did not post about it at first because I did not want to end up with water all over the place and have to reply to my own post that this was a disaster. I am happy to report that this has not happened. This mod is not really anything new. It is a small improvement on mod 1 and 1.a. Comparing it to mod 2., it offers less intuitive flow control over the start of the extraction but more intuitive flow control over the end of the extraction. That said, I have learned to control the flow at the beginning of the extraction when needed and I have also used the programmable preinfusion feature of the BDB to handle flow control over the beginning of the extraction for me. I will not argue that it is better or worse than any of the other mods but I will say that it has worked well for me.
A picture is worth a thousand words. So I give you pictures in addition to all my words
Enjoy!
Demo Video: Operation overview with blind basket Demo Video: Lever style shot
(coffee was not dialed in, so the shot flowed real fast! this was just for demo purposes) Demo Video: Slayer style shot Note about the videos: the shots pulled in the videos were done with a fairly empty water tank. In some of the videos, if you listen carefully, you can hear the flow of water going back into the tank. You really only hear this when the tank is fairly empty. It is not a disturbing sound at all and it is barely audible with the pump running. I just wanted to point it out and let you know that with more water in the tank, you don't hear it.
