PeetsFan wrote:Try pulling some dummy shots using the cleaning disc wrapped in plastic wrap (no cleaner of course). Take several. Does the pressure gauge show consistent results each time?

Why the plastic wrap, if I may ask? When I backflush using the 1 cup filter and cleaning disc, the pressure maxes out at around 9.5 bars. The pressure oscillates slightly around the 5 bars, which I am told is normal behaviour of the overpressure valve.

When I brew my espresso, the pressure never caps put at the 9.5 bars that my overpressure valve is set to.

Because Breville's cleaning disc has a hole in it. Breville recommends the plastic wrap for testing the pressure of their machines.

The cleaning disc that comes with the dual boiler does not have a hole in it. I know it's true for some of the other models.
I just wanted to make sure that there was not another reason I hadnt thought of

Marshall's suggestion of pulling a few shots with the blind disk (cleaning disk) is a good one. It will help you rule out the machine as a cause. Four or five back to back with a 10 second pause between them should be fine. Be sure to take out the portafilter and dump the little bit of water on top of the disk between shots. This will ensure that the pressure ramp up is the same between the blind shots. The machine should come up to pressure and then sit at a fixed pressure while the OPV governs the maximum pressure.

If this yields consistent results, then I would suspect your technique. Just because your bottomless pours do not show obvious channeling, does not mean that channeling is not happening. A video of your routine and pours would be helpful to diagnose technique issues.

We are here to help!

These are all VERY good suggestions. BTW, I recommend the $2 blind stainless "basket" from EPNW for doing back flushes.

I'm going to saw it's a combination of technique...make sure the puck is level AND the WDT is performed in a "spiral/figure 8" manner, not just round and round. It should be retention from a Niche...with 2 lift and dropped plastic cover motions, I get .1 gram retention. With a puff from my lens cleaner thingy, ZERO retention.

The blind pressure test (make sure to have things set to ZERO Pre-infusion time) done 3 times consecutively for 16 seconds will be the way to go...IMO. They should be EXACTLY the same. Remember to remove the PF and dump any liquid prior to the next back flush.

lancealot wrote:Marshall's suggestion of pulling a few shots with the blind disk (cleaning disk) is a good one. It will help you rule out the machine as a cause. Four or five back to back with a 10 second pause between them should be fine. Be sure to take out the portafilter and dump the little bit of water on top of the disk between shots. This will ensure that the pressure ramp up is the same between the blind shots. The machine should come up to pressure and then sit at a fixed pressure while the OPV governs the maximum pressure.

If this yields consistent results, then I would suspect your technique. Just because your bottomless pours do not show obvious channeling, does not mean that channeling is not happening. A video of your routine and pours would be helpful to diagnose technique issues.

We are here to help!

Well, I didn't see your posting, but I guess I didn't confuse our OP too much.

IMAWriter wrote:BTW, I recommend the $2 blind stainless "basket" from EPNW for doing back flushes.

With all due respect, there is absolutely no reason to purchase such a thing. The included rubber cleaning disc works perfectly and is much easier to insert/remove than a separate basket.

sorenwrang wrote:The cleaning disc that comes with the dual boiler does not have a hole in it. I know it's true for some of the other models.
I just wanted to make sure that there was not another reason I hadnt thought of

Sorry; I didn't know that they changed the disc.

sorenwrang wrote:I have made two espressos today (a few hours apart) using exactly 20.0 grams, in the basket, of ground coffee (same bean ofc). The first shot was 40 grams in the cup in 25 seconds, whereas the second shot was 33 grams in the cup in 28 seconds.
For both shots the coffee was carefully prepared with WDT, levelling and the same tamping pressure.

Because the shot is flowing fast toward the end, those are not super far apart in terms of time. If you had pulled the second shot to 40g, it would have only been a bit longer in time.

It may not happen with a conical, but with my MAX, the shot runs a bit faster when the grinder is cool (our house is often 64 °F or less). I have to make a very tiny adjustment before the second shot or if the house warms up naturally later in the day. If you combine this with slight variations in puck prep, it's one possible explanation of what you are seeing.

I know I am not supposed to mention the NZ having anything but perfect performance haha but I have read threads about the grind changing on its own while grinding. I have also read that the motor mounting screws can come loose if they forgot locktight at the factory. Just something to check if everything seams in order