# Adjusting OPV on a Classic



## Osh

Mazza's recent comment about adjusting the OPV got me looking at the various other forums out there, and the mods people have done.

In particular, this thread at coffeesnobs goes into a lot of detail.

Has anyone tried adjusting an OPV before (on a Classic or indeed any machine)? Would there be any benefit in messing around with the adjustment to see if my machine can be improved? (I don't have any obvious issues at the moment, just an extreme urge to fiddle with anything technical.)

Just to be clear, I don't use the single basket, or make ristrettos.


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## Osh

Well, I couldn't wait for the replies to come in so spent a good part of the day browsing various forums and threads and took the plunge and did the mod this evening.

First findings showed that the machine was working on 11 bar pressure. This basically means that the OPV (over pressure valve) was set to a point where it would allow the pump to build up 11 bar of pressure before it allows the water to return to the tank. In short, you are not getting the 9 bar ideal brewing pressure.

I was getting 160ml/min through the return pipe with the blind filter fitted. If you look at the graph for the E5 pump you can see that this equates to 11 bar.

A small adjustment of the OPV to 240ml/min brings the tension down to maximum 9 bar.

And the difference is unbelievable. The shot is thick and silky right the way to the bottom of the cup. It has a totally different mouthfeel.

I will need to mess around slightly with dosing, grind and tamp to get it spot on.

For anyone who likes to tinker, this is a simple modification that takes 30 mins.


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## DonRJ

Interesting piece of empirical research there Osh, your results clearly making the adjustment worthwhile, it would be interesting to have one of these http://www.bellabarista.co.uk/coffeespareparts/proddetail.asp?prod=301&cat=34 attached to measure the pressure at the brewhead following your OPV adjustment. Rather expensive though for something one would use only very occassionally.

Next, you should add my £5 digital thermometer mod as described here http://coffeeforums.co.uk/showthread.php?2305-Report-on-my-Rancilio-Silvia-cheapo-thermometer-mod for brew and steaming temp timing and monitoring.

Don

Don


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## Osh

You can make one of those pressure guages yourself, for a lot less money. Wonder what size the thread for the spouts is in the PF bottom.

Apparently the mod is also mentioned on that forum for the Silvia as well, though it's not so straight forward.

Since I haven't had the Classic that long, I haven't got round to measuring temperature yet, though it should've been the first thing I did.

Is temperature as a big an issue on the Classic as it is on the Sylvia? I'll have to do the "polystyrene-cup-under-the-group-head" test to check.

Did you find a big difference in the taste of your coffee once you started using your thermometer?


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## Mazza

Osh said:


> Mazza's recent comment about adjusting the OPV got me looking at the various other forums out there, and the mods people have done.


As a newbie and with my recent experience I'm just glad to have nice coffee and clean walls at the moment but this looks like a future project.....


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## DonRJ

Osh-----------> No big difference in taste as I was already doing the temp surf thing anyway, but it is an aid to getting the timing spot on for the shot so greater consistency and also timing steaming to ensure max power by having the element heating throughout the process. Worth a fiver for that and no need to go to the expense of a PID now.


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## Mazza

Just measured mine using the blind basket and I'm getting 100ml in 30 secs which is close enough for me at the moment as I've got to sort my grind yet !


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## Osh

Turn it down a little more and you'd be amazed at the difference in mouthfeel.


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## Mazza

Osh said:


> Turn it down a little more and you'd be amazed at the difference in mouthfeel.


Shouldnt it be turned up to 120ml in 30 secs ?


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## Osh

Same thing, I meant turn down the pressure to 9 bar, which will increase (turn up) the flow rate.


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## ChiarasDad

Osh, I'm having trouble releasing the OPV nut. How much force did yours require? And did it loosen anticlockwise, or clockwise?

(Thought I posted this earlier but maybe I didn't or maybe vBulletin ate it







)


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## Osh

I assume you mean the main nut (brass one) that the return pipe comes off.

It's tightened very well in the factory, you will need a lot of force. Turn in anti CW from memory. Try and use a short 17mm spanner, you might need to angle it up slightly as depending on it's length, you won't be able to place it perpendicular to the nut as your spanner will probably hit the side of the machine. Be careful not to round the nut, as it is soft metal.

Also, pull out the return pipe from the hole where it feeds through the base to the tank, it will give you more manoeuvrability. And lastly, watch out for the small O seal on the nut.


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## ChiarasDad

Thanks. Yes, I was getting some slippage with my adjustable spanner so decided not to force it, and have a fixed spanner set coming in the post tomorrow.


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## Osh

You're not going to get anywhere with the adjustable spanner. You'll end up damaging the solenoid as you rotate it.

At least you're patient enough to wait...


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## Twysted

I would love to start tinkering with my classic but as it is only a fortnight old Sarah would put two objects that are very dear to my being in the steam and ask me to measure the pressure with scalded nerve endings.


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## Osh

ChiarasDad ----------> any luck with the spanner??


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## ChiarasDad

They weren't in Thursday's post







I'm hoping for today. Will absolutely post what happens.

I also owe the forum reviews of assorted kit recently acquired: the PID, bottomless PF, and dosing funnel. With luck all will happen this weekend.


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## ChiarasDad

I've completed the OPV adjustment. A 17mm automobile tyre socket wrench finally gave me enough leverage to loosen the dratted nut and reach the adjustment socket.

I have an Invensys pump, which is less well documented than the Ulka pumps, but I relied on a coffeegeek post that suggested a bypass flow rate of 250ml/minute would be about right. It's now set right about there. My previous flow rate was something under 100ml/minute, so I've been working with quite high pressure up until now.

Since the mod I've pulled two shots so far: one with a favourite, well-understood espresso (MacBeans Espresso Gold) but from a bag that probably peaked last week, and one with a new-to-me espresso (Blue Bottle Hayes Valley) that's fresh but that I'm not experienced with. Both were quite good shots (indeed, I was surprised to get anything at all bearable from the old Espresso Gold beans at this point), so I think I've got my pressure in a pretty good range now.

I may try further pressure tweaks after I've gotten more experience with the present pressure level, but at the moment I'm quite happy just with this initial round. Thanks again, Osh, for all your help and encouragement.


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## Osh

Wow, that equates to a factory setting of nearly 13 bar.

I actually got hold of a flow rate graph for the Invensys pump from these guys. As far as I remember, the flow rate was different from the ULKA pump.

I've read somewhere that best results are around 10 bar, but I haven't tweaked it back yet. Maybe over the next week or two, I'll experiment.

Glad I could reciprocate.

PS. BTW, your inbox is full.


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## ChiarasDad

Thanks; I took care of the inbox a few minutes ago.

The pressure graph I used was here (the green line), linked from the post I mentioned earlier. While I don't know how much I trust it, the results so far seem pretty good, so I imagine at this point I'll make further adjustments by taste, as needed.


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## KRW

Hi all, is there an easy, online guide with (hopefully) pictures of someone doing this mod? I'm convinced the pressure on my new-ish Classic is set waaay too high.


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## ChiarasDad

I got my details, and what pictures I found, mainly from these two links, I think.

http://coffeesnobs.com.au/YaBB.pl?num=1143118905

http://coffeesnobs.com.au/YaBB.pl?num=1175171794/0

Best pictures I found (these came from the threads linked above):

http://coffeesnobs.com.au/attachments/P1050237_1.JPG

http://coffeesnobs.com.au/attachments/P1050238_1.JPG

The gist is:

- Open machine (after disconnecting power, etc.).

- The boiler will be unmistakeable.

- If you are standing in front of the machine, the OPV will be straight down, just to the right of the boiler, with a clear plastic hose coming off the top.

- Remove the hose (you can just gently tug/tease it off).

- Unscrew the top of the OPV (takes a *lot* of force).

- Use a hex key to adjust the OPV setting inside the valve body.

- Reassemble (you don't have to tighten the OPV top quite so much on reassembly), reattach hose, close up the machine.

- Test.

- Repeat as needed.

Tools:

- 5mm hex key

- 17mm socket wrench of some sort. I used a tyre changing tool.

Give a shout if you need help!


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## KRW

Thanks ever so much for that. I'll do a bit more digging around/practice before attempting, I think. I'm only learning so think there could easily be other factors to my 'speedy shot' at the moment.


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## espresso_a_day

KRW, if you have a blind filter basket you could start by measuring the flow rate -- before unscrewing/ adjusting anything -- and see how far off you are from the desired setting at the moment. You would have to open the machine to see the pump model. That's easy though and actually quite fun to look inside (make sure you unplug it first).


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## omega

Which way do you turn the hex head screw to change to 9bar also how much do you turn it..


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## Glenn

Before adjusting make sure that your technique is correct

It is rare that you will need to alter the setting

I note from previous posts that the machine is new to you.

Work on tamping/extraction before starting to adjust. The re are normally other variables that require attention if the coffee you are drinking is not up to the expected standard


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## omega

Thanks for that I was just interested in how and why this is done..


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## Osh

omega said:


> Which way do you turn the hex head screw to change to 9bar also how much do you turn it..


Counter C/W turn for lower bar setting, C/W for higher bar setting.

The 'why' it is done is to extract at the best possible pressure. You'll see a massive different in mouthfeel of the shots. Apparently it also greatly improves ristrettos as well.


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## KRW

Glenn said:


> Before adjusting make sure that your technique is correct
> 
> It is rare that you will need to alter the setting
> 
> I note from previous posts that the machine is new to you.
> 
> Work on tamping/extraction before starting to adjust. The re are normally other variables that require attention if the coffee you are drinking is not up to the expected standard


Yes, definitely, quoted for truth. My speedy shot problems, above, were caused by a crap grinder (see For Sale section







)


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## carbonkid85

Sorry for bringing this thread to life again, but I don't seem to have the right tool to get the nut off the OPV without damaging it.

Would a 17mm box spanner such as this http://tinyurl.com/6yzt4c6 do the job?


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## PaulN

Sorry to be completely wet here, but how do you check your flow rate? Do you have your blind filter in and run the machine but i guess if its returning to the tank you need to measure the amount returning?

I thought it was bad for the pump to be ran for longer than a few seconds with the blind filter?

Finally, is it about 120-125ml per 30 secs for 8-9 bar?

Thanks

PaulN


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## ChiarasDad

carbonkid, it looks like it ought to do it. 17mm is the right size, and the driving rod in that kit will help you get the torque you need. I had to use a LOT of torque.

As for the volume/pressure equation, I wish I could help -- I had to look all that stuff up back when I made the change on mine, and I don't remember the figures. However once you've opened the thing up one time, subsequent adjustments are much easier - so you can set the pressure to what you think is right, observe the results, and try going up or down a bit if you think you got it wrong.


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## CoffeeExmoor

Thanks for all the info on adjusting the OPV. I can see all that but, like PaulN, I can't fathom how you check the flowrate. If you've actually got water in the tank, how do you check the flowrate back into the tank? I'm sure it's straightforward but, as a newbie, it's beyond me at the moment! Thanks


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## espresso_a_day

There are two rubber tubes normally hanging into your water tank. You need to identify the tube through which water flows back into the tank if pressure gets too high at the OPV. I don't remember how it's identified but I'm quite sure one of the OPV adjustment pages shows a pic.

You put this tube into an empty measuring container.

The other tube, the one that actually pulls water from the tank into the boiler, stays in the tank filled with water.


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## carbonkid85

Box spanners failed. I just can't get into this OPV! ha.

I think I shall give up for now and just concentrate on making sure my technique is EXACTLY right.


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## PaulN

Hi All,

Well im going to have ago at this at the weekend! Thanks to AndyL for lending his pressure gauge so i can do it right and hopefully make the right adjustments.

Ill update how it goes.

PaulN


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## AndyL

Guys I put this together. hopefully it will help.

http://coffeeforums.co.uk/showthread.php?p=18565

Sent from my iPhone using Tapatalk


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## garydyke1

Ill be trying this once my machine comes back and is confirmed as working 100%.

I really dont give two hoots about invalidating the warranty, lol, Ive found it is worth nothing but trouble


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## AndyL

Well PaulN is in possession of my gauge atm. if you or anyone else wants to borrow it then we could pass it around.

Sent from my iPhone using Tapatalk


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## garydyke1

Thats very kind


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## PaulN

Thanks Andy that a cracking write up. I had mangled one togther from Coffeesnobs but yours is much clearer.


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## arjxh56

Can the OPV be adjusted on a Gaggia Baby Class?


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## mharvzzz

how do you guys measure the water volume of the OPV return?

If you use the blind filter back flush method, should the water *coming out going to the drip tray* be measured as well?


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## ashcroc

mharvzzz said:


> how do you guys measure the water volume of the OPV return?
> If you use the blind filter back flush method, should the water *coming out going to the drip tray* be measured as well?


It's alot more accurate measuring the pressure with a portafilter mounted gauge.


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## solomonosteroe

Adrian from Shades of Coffee suggested I hit the user groups to see if anyone will lend portafilter mounted pressure gauge? I could purchase, but I just need to set the pressure on my pre-2015 Classic, and I only need to do it once. I'll pay shipping obviously, and I live in Vancouver Canada. Thanks for considering.


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