# Rocket Giotto Evo 2 - Brew Pressure too high?



## big dan

I just noticed something and not sure if it is something i should be worried about.

The manometer on the right that tells you the brew pressure at the pump starts at about 8-9 bar for the first 5 seconds when brewing but then it increases to about 11-12 bar later on in the shot.

Am i right in thinking that the brew pressure should stay at around 10 bar max throughout the shot or not? I am thinking that maybe i need to adjust the brew pressure that is on the underside of the machine but wanted to check if anyone else has had this problem before or if there is another cause.


----------



## El carajillo

Try with a blind filter to get a truer reading before making alterations


----------



## Wobin19

For comparison I have the same machine. Mine reads 8 bar for first few seconds then tops out at 9 during the rest of the shot. That does seem high. I get the same range with the blind filter.


----------



## big dan

Yes when i use a blind filter the pressure starts at 8-9 and increases to 12 bar. Think i am going to see if i can adjust the pressure as this seems way to high!


----------



## DavecUK

big dan said:


> Yes when i use a blind filter the pressure starts at 8-9 and increases to 12 bar. Think i am going to see if i can adjust the pressure as this seems way to high!


*Check they have not moved the pressure take off point for the pump.. It used to be before the 1 way valve* which should prevent the pressure peaking after an initial rise, due to expansion of water. More information on the phenomenon below

http://coffeetime.wikidot.com/pressure-measuring-portafilter-rising-pressure

The easiest way to check I suppose would be to do this with a cold machine..e.g. immediately after you first switch it on (or disconnect heating element). This totally discounts water expansion in the brew system.


----------



## big dan

Thanks for the link Dave. I think i have the opposite problem though as the gauge reads the pressure at the pump not the brewhead which means the before it even gets to the grouped it is being pumped in at 12 bar.

I had a look at the screw under the machine and the bolt securing was loose enough for me to do it by hand so i wonder if the screw has moved at all over the last year. Just adjusted it a little and from my next shot started at 7 bar and rose up to a steady 9.

Thanks for the advice and one final question. If 9 bar pressure is the optimal should my machine be reading 9 or 10 bar? I remember reading somewhere that the gauge might be reading static pressure instead of line pressure (forgive me if this is completely wrong!) so people often set their machines to max at 10 bar on the gauge as this will actually be 9 bar that is reaching the grouped or there abouts.

Gonna do some taste tests now to see what difference it makes!


----------

