Function over Form - Couplers
For many things, the form follows the function. For example, most chairs have the same basic shape to they can support the patient well and allow good access by the operator. Sometimes, the form belies the function or reflects a different function than may actually be required by the end user.
The photo below shows a very common type of plastic coupler. The form of this coupler allows it to be easily disassemble, disconnecting the two lines from each other. The reason for this form, is to allow easily attaching lines when installing the equipment. In reality, once installed, there is no need to ever pull these lines apart again, so this form and function become obsolete. As these are plastic couplers which use thin connections, it’s very common for them to break. When replacing such a coupler, it is best to use a more permanent style of coupler, as the ability to pull them apart is not part of their current function. A metal barb union is generally a better choice as they are less fragile and arguably hold better. Of course, if you look at the photo closely, you can see one end of the hose joined by this coupler is very short. There may be enough slack to simply cut the coupler off and attach the long end of the hose directly to the valve.
The flimsy nature of this coupler makes it poorly suited to a permanent connection
With the vast array of different valves, connectors, blocks and fittings, it can be difficult to keep things straight. It’s often simplest to match what you have, but sometimes, if you take a moment to reflect on what something does (this is clearly just a connection between two hoses) you may find an easier solution.