Hi.

I recently bought a used lever machine. Whenever I use it, before pulling the first shot, I pull some hot water through the group with only the portafilter on, without a basket. The color of the water is never completely clear... it also has some coffee grounds suspended in it, probably left over from prior pulls (only a few particles, but they are there). Is this normal? How badly does it affect the taste of the espresso?

I tried to "fix" this by removing the shower screen, and cleaning it thoroughly, as well as wiping the visible part of the piston without removing it completely. The shower screen was definitely in need of a cleaning, lots of gunk, probably lube, covering a big part of it. Also, after each use, I give a good wipe to the shower screen and around it with a wet paper towel. Anything else that needs to be done?

All help is appreciated!
Thanks in advance.

I have a Pavoni and it can pull back grounds through the screen, I dump the tank regularly and remove and clean the screen like you mentioned. If its a pavoni you recently picked up I would also remove the piston and clean it real well, regrease and re install. I pull a shot or so of water out before I pull to get any residual grounds out, if its discolored I'll pull some more until its clear.

I haven't noticed any taste difference as I make lattes with it. A true espresso connoisseur might have issues with it, I just keep it as clean as I can

I think you are on the right track. You might start doing a little flush right after shutting the machine off, while it still has pressure, to help clean the shower screen. Then every month or two pop the shower screen and give it a cleaning - you could do it more or less often depending on how it looks.

As part of my routine I always bring the group and PF up to temp (and heat the cup a little) by doing very small flushes (and waiting a few seconds between each.) The water is clear, and rarely do I see any stray grounds in the cup or PF basket after doing this.

On my sama, water from the group is often as you describe, but water from the boiler tap is clear. It's oils collected in the group that you're seeing. It does impact the taste of the espresso, so keep it clean.

for a moment I thought we were going to have another Magenta water episode.

Used Olympia Cremina has magenta boiler water

looking for that thread reminded me, who was it that found their boiler was completely filled with a sodden gooey mass of coffee beans by the previous owner?