ethom Senior Member Joined: 24 Nov 2012 Posts: 66 Location: Pittsburgh Expertise: I like coffee
Espresso: Gaggia Carezza, Gaggia... Grinder: Vario Drip: Bosch
Posted Mon Jan 28, 2013, 4:54pm Subject: Re: NS Oscar..Microfoam..Group head temperature..
Neither Home Depot nor Lowes carries a valve that would work for Oscar’s drain. An old fashioned neighborhood hardware store did have a ¼” ball valve that might work, but how to know if the threads will match?
After some research, I'm pretty sure the pipe fittings on Oscar and most European espresso machines are called BSP for British Standard Pipe. BSPT is tapered where the thread diameter gets a bit bigger toward the fitting body, much like US pipe threads. BSPP is parallel where the threads stay the same diameter throughout the spiral. US standard fittings are called NPT for National Pipe Thread. FPT (FNPT) and MPT (MNPT) simply denote female or male.
Ideas of whether to mix BSP and NPT fittings are also mixed. Some seem to think it’s just fine in low pressure conditions, say under 100 psi which I think would include HX boilers. Other info that provides specific thread profile data (angle of the “V” and how the peaks and valleys are cut) and pitch (threads per inch, which changes with the fitting size) show that differences exist. Only ½” fittings have the same thread pitch between BSP and NPT; all other sizes differ. Image of a PDF file attached below (can't seem to get the PDF to be viewable). The “go ahead” camp says that plumbers tape will make up for any differences. Others say that if pressure holding is critical, don’t mix the types. Considering that brass is a relatively soft metal and threads can be deformed, I lean toward staying consistent with the machine and using the proper type for the application with no plumbers tape if it can be avoided.
To that end, I found a site that sells BSP valves pretty cheaply. Like many products, they are made in China and shipped direct from there, meaning I’ll see my valve in a few weeks. But with Oscar now descaled, there is no hurry. Here is the one I’ll try: Click Here (www.aliexpress.com) It has ¼” BSP female threads that should fit the drain pipe and a hose barb connection to which some plastic tubing should fit by friction. They had 8 and 10 mm barb connection options.
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