I have been a happy user of my espresso setup for several months. We have an Isomac Zaffiro, with naked pf, and a Mazzer Mini. Getting delicious shots with good even pours has been no problem at all.

Around five days ago, my first shot of the morning was a disastrous channeling nightmare, with both pinhole-style spritzes and general uneven, fast flow, the nightmarish bubbling/gushing pour I'd heard so much about...

And every shot since has been the same. I've moved the grind around, changed the beans, backflushed the machine. Every single shot has been a much worse pull than any other shot I've ever made in the previous six months of owning this machine. And my wife has had the same experience, so I don't think it's down to a sudden change in my technique.

Any ideas what might be causing this, please?

I've noticed that the grounds coming out of the grinder have been falling in clumps, perhaps slightly more than before. Could a greasy grinder be the problem? I've got some grinder-cleaner in the mail, but it won't be here for a few days. I'm also going to give the machine a de-scaling as soon as I can get my hands on descaler.

Any ideas for things to try to diagnose and remedy the problem would be more than welcome.

Thanks a lot!

Guy.

If nothing else has changed in your machines or prep, my first guess would be a stone gone through your grinder, wrecking the burrs.Did you hear your grinder making bad crunching noises? i've had this happen, its more common with home roasting, as pro roasters usually have de-stoners etc. It might be worth checking your burrs for signs of damage, and while they're out give them a good clean, dry and re-assemble

Did something happen to your overpressure valve to make your brew pressure too high?

Thanks for your replies. To close the loop: I took the plunge and disassembled the Mazzer Mini, which was fairly well clogged up with old coffee. Cleaning all that out improved the distribution quite a bit and the channeling was immediately reduced, and then a thorough backflushing of the machine put everything back to normal. In fact, better than normal because I'm now taking even more care over distribution.

Some delicious shots in the last week!

Moral: keep your grinder clean!

Guy.