My OPV adjustment journey.

When I say ‘My OPV adjustment journey’, I do mean MINE !!!

Steve has got really really busy working on a secret squirrel project and I was getting sick of sink shots and crappy tasting coffee, as much as he seemed to think it tasted ok.

Soooooo I got home from work today and thought stuff it, I can adjust the OPV myself.


OK so here we go for the journey of how to adjust the BES900 OPV.

A good idea is to get hold of a Sunbeam Dual Filter, these consistently correctly show whether or not the gauges are working correctly, this works on a lot of machines, before I returned the EM6910 I was able to test the gauge on the BES900.  It came out at 9 bar, so concluding that the gauge IS working correctly.

The first step is to test the OPV pressure with a blind filter.  These filters are available from all sorts of places from coffee accessories online stores to the best roasters in Australia 😀  Thanks Jeff (mycuppa).

Mine tested between 12.5 to 13 bar.

First undo the screws.

I found that it was easier to start with the two screws on either side of the group head, these are just philips head screws, they hold the top panel in place.

The next two are on the corners of the back panel that says Breville.  These screws are Torx head screws, make sure you have the right screw driver so you don’t destroy the head and no we have the correct tools so we didn’t damage anything.

This allows you to pull the top panel away from the back panel.  Before you do this take the water tank out, when you do this you will see two screws at the top of the open space and the bottom right of the Breville panel that you just took the last two screws out of.

These screws are again just philips head screws.  Please take note that there is a long and short one, the long one goes into the left hand hole.  Once taken out you can now take the top panel off, lifting the top panel to allow for that to happen.

The back panel can be placed on the bench top without stretching or breaking the wire, well I found I could do that.

In the above photo you can now see the white plastic OPV sitting at the top left.  Below is a closer view.

Again make sure that the machine is switched off and unplugged.

I have had a fellow coffee enthusiast use this guide (see the comment) and they suggested a few additional instructions which I will add here.

The first thing you need to do is slide the silver hose clamp, use a pair of pliers to squeeze the clamp together which enlarges the clamp circle around the hose and you can slide it down the hose away from the OPV.  Next you need to take the hose off the OPV.

If the hose is really tight (mine was) you can use pliers right up near the fitting (as close to the cog as you can get) and wiggle the tube back and forth. That will help expand the opening and make it easier to remove.

What you will see now is a clip that sits over the adjustment cog.  You need to remove this, it has raised sections that keep the clip on where the square sections are, see below photo without the clip showing the raised sections, this can be a little difficult but just be careful and it comes off easily.

If you can’t unclip the clip around the OPV cog, you can gently rotate the entire T-joint clockwise towards you. Then you can reach both sides of the clip more easily.

You’ll also notice in the above photo that there are lines drawn on the adjustment cog and the main section of the OPV.  These I assume are done during production.

As you’ve seen in the first photo this setting gave me the 13 bar pressure.

Due to not being able to move this cog by hand (fingers) I couldn’t tell which way was tighter than the other.  I tried going clockwise first, I went one full turn, I tested with the blind and the pressure was off the dial.

Oh one thing I should add here is, remember to put the hose back onto the OPV when you are testing it otherwise you end up with water everywhere and that can be a dangerous thing.  The other thing is be careful with your fingers when pulling the hose on and off, boilers are hot and can burn, and yes I am a clutz and have a blister!

I put it back to the original position and tried the other way.  I went one full turn anti clockwise.  The blind tested at 11 bar.

11 bar I still feel is too high, general consensus is that once you run a shot with coffee the pressure will come down.  I then did another adjustment to one and a quarter turns anti clockwise.  Hopefully you can see on the below photo the line on the adjustment cog sitting half way between top and bottom.  It is the bottom dark line, not the dirty marks from the pliers at the top.

This adjustment resulted at a reading of 10.5 bar, which at present I feel is where I want it to be.

Now it’s time to put everything back together, just do the opposite of what you did to take it all apart.

Do be careful putting the back panel back on as the wires are a little messy and they can get caught in places you don’t want them and if you force it you could damage them, if you get one caught and pinch through the insulation you could make external parts live which could be deadly, take it easy and it will all just slot together.

My next step was to do another blind test, this time it came in at 10 bar, honestly I have no idea why it changes but I can only think it has to do with everything sealing correctly once the hose and clips are all put back on.

The above turned out to be completely fine.  I was ready to try an actual shot.

I am using my Spong No.1 to grind.  I measure out 20 grams of 16 day old beans, this particular blend is best from 12 days so 16 days is perfectly ok, grind and pack into the portafilter.  I think I might tamp too hard but it’s a matter of getting the grind and tamp correctly for what I feel is the best taste for me.

Here is the pressure during the shot.  I’m quite happy with where it is sitting.

The following photos are during the second shot I did.  The first shot I tried as an espresso as I had tried the same bean and grind during our original adjustment attempts.  This time the bean showed it’s suuweet notes 😀

This shot is with a different bean, photos of the shot during and after extraction.  Extraction time was 60ml in 42 seconds including the 8 second pre-infustion, so 34 seconds for the actual shot.

Finally here is my attempt at latte art 😀

The bean I used is best with milk so this was the only way to try it.  The taste, was smooth with hints of berry.


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