It’s a short one today: I have been looking into the options for plumbing my next machine. Do I want the solution to be totally bomb-proof? Easy to assemble? inexpensive? Some options follow.
Copper and compression fittings
My first espresso machine was a salvaged 2 head CMA beast that I got for scrap from a cafe in my neighborhood after the boiler manifold ruptured, shearing off several large cap screws. It used copper for plumbing (see the picture above), and included every imaginable gauge of pipe and connector style. This made it a nightmare to work on, and difficult to get it water tight. Still it was an interesting introduction to how espresso machines work. Copper until recently remained the most popular way of moving water under pressure from one part to another in the espresso world.
Recent copper based machines use modern compression fittings to connect pipes from one part to another, reducing the complexity a little bit. Or custom gaskets, or o-rings and custom seats. These fittings are typically made of brass.
Stainless Steel and compression fittings
More and more modern machines seem to use stainless steel tubing (sometimes called Inox). These machines also favor compression fittings like older copper machines, but in this case the fittings are also made of stainless steel in order to avoid reactions between dissimilar metals.
Copper is easier to bend than stainless steel, but it stainless steel can still be hand worked and cut with a good tube cutter.
Plastic tubes and push-fit connectors
Modern home machines like the Gaggia Classic Pro use plastic tubing and simple clamps to attach the tubing to different parts of the machine. Recent machines use a braded silicone hose with an ID of 5 and an OD of 9, but older machines used a Teflon (PTFE) tube that is 5 mm ID and 6 mm OD. That is what I used in my machine, and it seems common in other home machines as well.
I’ve come to like the Teflon tube - it works well with push-fit connectors which are amazingly inexpensive and easy to use. As dodgy as they sound I’ve had two machines now that use them and they have held up well.
6 mm may be a little small for the main pressure lines of an espresso machine, and in fact Gaggia switched to the larger braided silicone hoses in their more recent machines. Silicone does not work with push-fit connectors, but instead uses simple wire compression clamps to attach to other fittings. Push-fit connectors also support PE (Polyethylene) tubing, which performs similarly to PTFE, but has a lower melting point which seems like a problem waiting to happen.
Conclusions
I have a some 6mm PE that I want to use up, and have already invested in both steel and plastic push-fit connectors that fit the pressure sensor, so I think I’m going to go with what’s on hand. Someday I’ll make a “finished” version of this project and it might make sense to use Inox. I’d like to have the experience of working with it, but I know from experience that using compression fittings requires some design up front to maintain tool access (you need a wrench and significant torque to make them work) and keeping the part stable while that torque is being applied can be a challenge.
I always want to hear what you think, but I’m particularly interested in what you think about todays topic. If you have a better solution, let me know in the comments!