I have an old unit, the hose of which had sprung a leak, making it impossible to use the brush. Calcium deposits make it almost impossible to remove the retaining rings, so the knurling is damaged, and the rings are out-of-round and have to be replaced. I did not carefully note which end of the plastic tube with spring goes to the tank and which end goes to the flared copper tube. I hope I put it back on correctly. It was not clear which side of the venturi was the spring side, so I had to install the button twice. The instructions were not clear as to what was the "spray tube assembly". The nut on the assembly seems to be locked in place with the rest of the assembly, so I have been unable to adjust the direction of the spray. The nut has to be tightened VERY tight against the handle, or else water comes out the other end of the handle. I am not very handy with tools and putting things together, so that added to instructions that were not entirely clear, it took me a long time to get to the point where I could test the system before putting the cover back in place, which will have to wait until I can order the retaining rings. Good think I had all the tools I needed. There was no required tool list, unfortunately.
Had faucet for 3 years and discovered soap leaking from copper tubing in black hose assembly . Small hole from corrosion where clear tubing (hooks to soap dispenser) connects to copper tubing. Actually broke off. Won’t think copper tubing would corrode like that.
Copper tubing is not bullet proof. Some contributors to copper corrosion: chloramides in municipal water, salt, acidic well water and, in the specific case of the part you mention, if the detergent you use has a citrus additive.