Hi, I have an Expobar Brewtus Espresso Machine, Double Boiler Rotary Machine.

I read that the optimum brew pressure is about 9bar.

My machine is connected to a water tank and I noticed that my brew pressure is always at about 6bar. I have further read that to increase the brew pressure, I could adjust my OPV. I have tried that, and noticed that the pressure did increase (up to the full 15bar) when I leave the machine alone (ie. not extracting coffee). However, once I turn my lever and extract the coffee (ie. pressure water passes through the grinder coffee), the brew pressure goes back to 6bar.

Is there something wrong with my machine, settings etc? Any advice would be greatly appreciated.

A quick way to check your brew pressure is to insert the backflush disk--you'll see no water flow--and then read your pressure gauge. If it's still 6 bar, you'll then need to adjust.

You mention that you adjusted the OPV, however you have the Rotary version of the Brewtus. An OPV is usually only applied with vibe pump machines. I assume you adjusted the internal bypass of the pump while trying to adjust brew pressure?

Regarding the pressure indication when the machine is idling, that does not necessarily mean anything. When the machine is not used, the water that sits inside the brew boiler and the steam boiler heat exchanger heats up and builds pressure due to thermal expansion. If your pressure gauge measures upstream the group valve, it will indicate whatever this pressure amounts to.

The video only shows flushing of the group. In this case there is no hydraulic resistance since there is no coffee, so you will not see the full brew pressure. Insert the blind filter and then run the pump. Then you can adjust the maximum brew pressure to 9 bar. See also the thread below:

How to adjust brew pressure of rotary pump espresso machine?

DeGaulle wrote:You mention that you adjusted the OPV, however you have the Rotary version of the Brewtus. An OPV is usually only applied with vibe pump machines. I assume you adjusted the internal bypass of the pump while trying to adjust brew pressure?

Exactly. The FAQs and Favorites has a section on rotary and vibratory pumps that elaborates on the differences, including helpful videos like How a rotary pump works and How a vibe pump works. To avoid confusion, I refer to the pressure relief valve as an expansion valve for rotary pumps and an over-pressure valve for vibe pumps, though technically the same part can be used for either purpose.

Thanks. I have circled (in the photo below) on what I have adjusted. Is that the internal bypass of the pump?

Also, will drawing water from a water tank as opposed to being plumb in affects the brewing water pressure?

I further read that I should be adjusting the knob on the pump itself. (http://coffeetime.wikidot.com/rotary-pu ... adjustment)

I am not quite sure which is the knob I should be adjusting. I have attached some photos, and any advice would be greatly appreciated.

Whatever adjustment you made to the valve you circled in red was both incorrect and not necessary. So, firstly, repeat this "adjustment" in the opposite direction. As an EXAMPLE, if you turned it 1/2 turn clockwise, now turn it 1/2 turn counterclockwise.

As others have said, what you adjusted was the OPV (acting as a thermal expansion valve) whereas you should have made the adjustment on the pump.

See this: Rocket R58 brew pressure problems.

Follow the instructions I wrote.

hslh1716 wrote:I am not quite sure which is the knob I should be adjusting. I have attached some photos...

The adjustment screw is facing the boiler, which makes it very inconvenient to adjust.You can see what the "pressure adjusting screw" looks like in this diagram:



It's facing away from you in the photos above. Now that you bring it up, I remember scraping my knuckles to adjust the pressure on the Expobar. I'm sure they had a good reason for installing the pump in that orientation (e.g., it saved them 10" of copper tubing ).

hslh1716 wrote:Also, will drawing water from a water tank as opposed to being plumb in affects the brewing water pressure?

Yes. From the FAQ: Water pressure and the effect(s) it may have on rotary pump.

Thanks for the very helpful tips and I have followed your advice. However, after turning clockwise to the maximum (cannot turn any further), the pressure is still only at 7 bar. Did I do something wrong, or is there something I could do? The pressure is very constant at 7bar, used a blind and it also showed 7bar. Could it be something wrong with my pump?

Very unlikely it has to do with the pump.
We can't tell much if it's not running on a blind basket. Is it from the tank or mains?

If I'm not wrong, the OPV you had adjusted will affect the idling pressure if that was your concern.
The valve to adjust the pressure on the pump is facing the boiler, and it has a nut that restricts, you will need a wrench to release before turning.

There's a locking nut you need to undo.

I ended up unscrewing the motor from the base to get better access to the pump, it was such a pain.