Hi all,

I've owned my used Silvia for about half a year now and although I never achieved the consistency I would've liked, I have got some really good results over the last few months. For the last couple of weeks, though, my shots have been simply awful. I'm not sure how to describe the taste, but the best I can manage is that the espresso always has a bitterness, even when pulling an intentionally underextracted (i.e. sour) shot.
Of course I first thought it was my own fault (grind size, tamping, temp. surfing, etc.), but I haven't been doing anything particularly differently, and over 2 bags of coffee I should have got at least a bit closer to getting something palatable, even if just by accident.
It probably also isn't the coffee. It's fresh, from a good roaster I've used before with good results and I did get decent results when using it for french press.
It could be my grinder, but the grounds don't look particularly different than before, so...

One time, I forgot to put the water tank lid back on and I noticed a steady trickle of water back to the reservoir. I never paid attention to this before, but I started looking into it. That sort of thing seems to point to OPV problems, but the internet is full of OPV-related threads, so my head is kinda spinning... Anyway, I found the test with the blind filter and the graph (How do I check brew pressure without a gauge?). I tried it I got about 500ml/min of flow back to the tank.

So, my questions:
Is it indeed likely that my OPV is indeed faulty and is the cause of the bad taste?
How are you supposed to inspect the OPV? I've opened up my machine, but the OPV is screwed very tightly to the boiler and I don't want to wreck anything trying to get it off with brute force. Also, I believe the previous owner adjusted the pressure to 9-10 bar and I'd rather not lose the setting if I can avoid it.

Right, that post turned out quite long... Hope someone is willing to read all of that and give me some advice. I'd be very grateful to be able to get my good espresso back...

Is the machine dirty? That usually causes a lot of my 'overly bittnerness' issues.

I have a Silvia now paired with a Baratza Preciso which gets the job done, I have moved onto bigger machines/grinders so selling this pairing. Now a couple of questions;

- Out of curiosity what kind of grinder are you using?
- How old are the burrs?
- Have you cleaned you silvia with the cafiza product, descaling?

The leaking back into the water tank is weird as it only flows back when your doing a shot, the whole opv thing, and there should be no pressure I think due to the 3 way valve or little pressure.

I typically used the double if not the triple basket with loads that varied from 17-20 depending. The shots all came out well, took a while, and with a naked porta is spewed a mess till I figured out how to get good shots. The grinder was a big key in this.

You can make a simple pressure tester. Take your porta and spin off the spout on the bottom, go to the HW store and buy adapters/tubing etc. to connect a simple pressure gauge (found in many places locally and online). Look online for more info but it was not that exoensive

Thanks for the replies!

@brianl: Is there a part I should check that would get especially dirty? I've been backflushing with cafiza about every other week, recently descaled it and I've soaked the portafilter in some cafiza.

@Ricbnw: My grinder is a mini moka demoka. It's stepless and seems to be decently rated... (http://www.minimoka.es/en/molino/molinillo-de-cafe/)
I bought it used, from a guy who sells used espresso equipment sort of semi-professionally. I have no idea how old the burrs are.

In any case, am I right in thinking that the water coming from the return line is not right? This would mean that the grinder is not the first suspect, right?
Any info on getting the OPV off, or is is simply not worth it unless I'm certain something's wrong?

Hi,

So I assume the trickle of water from the opv is only during a shot? If so that's ok as the opv is doing its job and may just need adjustment. If it leaks when the pump is off, continuously, then that's bad and the boiler would lose water or something...odd

I am going to assume only during a shot which is ok, the valve is doing its job. It may just need adjustment. As I mentioned its not hard to make a pressure tester, I would do that and its not hard to fiddle with the opv. Lots of video's but you loosen a lock nut and adjust. Use 2 wrenches and you're good.

You don't need to back flush the machine every week, I did mine months apart. The biggest part that gets really dirty are the screens on the brew head above the porta. Make sure you clean those.

All that said. What dose into the porta are you doing, how long the shot and weight of the shot after.

Typically I did 18-20g in, 25ish seconds and I would extract ~ 30ish grams out which is a restrained shot. Depends on the bean what it likes, for me.

Once you get all that solved, are you temp surfing? If so and you want an upgrade to help on that look at the Auber Pids.

Cheers

It does indeed only leak during a shot...
Thanks for the tips. I've given everything a good clean. Nothing seemed especially filthy, but we'll see.
I'll go get some fresh coffee and the pressure tester parts tomorrow and I'll report back.
Re dosing: usually between 16 and 17g, aiming for 25s and colour
A PID setup is not for now, they're quite pricey. At some point I'll probably get really fed up with the surfing routine and get one, but not now...

A good clean to your grinder is always a good idea to , remove the top burr carrier and take out all the stale gring that could be stuck there. It will also allow you to check the wear on your burrs.