After having the Rancilio Silvia for 2 years and experienced with so many different beans from all over the world, it’s time to backflush and pressure test the machine. Blackflusing involves a 58mm Blind filter ($9.99 CAD) and Urnex Full Circle Tablets ($22.95 CAD) at Green Beanery.
The details on how to backflush is so simple and there are tons of information on the Internet. Yet, the pressure gauge is another story. The pressure gauge portafilter kits selling on Internet are about $45 US, but most of them don’t come with a valve (i.e. maximum pressure testing only) but I want to control the valve (i.e. test brewing pressure when slightly opened). Unless you buy the kit ($60 US) that is designed to install directly connected to the pump, then you can see the pressure change everytime when the brew button is pressed. For me, portafilter gauge is good enough and inspired by this article: Rancilio Silvia Pressure Gauge Test, I decided to DIY one.
Parts: I picked up a fire sprinkler pressure gauge from Active Surplus in Toronto ($15 CAD), I think it was used but who cares. Notice that it said “Air/Water” and its Made in USA. Unfortunately it was not oil filled, it’s okay since it is not connected to the pump. The rest of the parts were from local hardware store Home Depot – because of the size of the fittings, I had to get parts from both plumbing (Watts) and air compressor (porter cable) departments. It was easy to assemble, simply put them together and sealed with teflon tape.
Notes: To perform the test on Rancilio Silvia, DO NOT use any basket otherwise it will leak on the grouphead. In the photo/video, you can see the position of the portafiler was way pass the normal position because no basket was used. This is the only way to seal it properly without leaking, as you can see in the video there was not even a single drop of water leaking from any joint or grouphead.
Test 1: Maximum pressure with valve closed: 150-152 psi (10.3 – 10.5 bar)
Test 2: Brewing pressure with valve slightly opened: 140-147 psi (9.6-10.1 bar)
Repeatedly running both test 1 and 2 for multiple times (see both pictures and video), passed with flying colors. As you see in video, it wasn’t easy to control the valve. The point is to test the pump is working fine and the machine has enough pressure to brew an espresso properly.
For most semi-automatic prosumer/professional espresso machines, having 8-10 bar (116-145 psi) is optimal. Read “The umpteen BAR Myth” section in Espresso Machine Buying Guide and How Many Bars Should an Espresso Machine Have? As you can tell, company like Nespresso have their machines built at 15-19 bar, definitely it’s a marketing gimmick. Very smart, the higher the number the better especially for consumers who don’t have advanced knowledge about espresso.