Step 3: Part sizeing
Its size depends on the portafilter basket that you get.
When you disassemble the union, the basket should fit into the outer ring just like in the picture.
The 2 O-rings go one into the PVC ring, then the basket, then the other O-ring.
From the picture of the finished machine, you can see that the big cap has to be about the size of the union’s outer ring.
In my case, the union I used was a 1-1/4” with a 2” cap.
Since the cap is bigger than the part of the union that is screwed into it, you will need a reducer to make sure that they fit tightly together. In my case a 2” to 1-1/2” reduce did the job, but I had to sand both pieces down to make them fit.
The Small cap will be the same size as the inner diameter of the reducer.
Please see the pictures of how the machine built to better understand how the part sizes come together.