I've encountered a Grohe single handle kitchen sink faucet that has no visable signs for diassembly. The handle on/off operation is about as stiff pulling out the proverbial Excaliber, but hot to cold is a breeze. Off/on is a push from left to right, and cold/hot is front to back. I'd like to replace the unit, but the customer has some sentimental value attached to it. Before I ask my local Grohe distributor how this is done, is anyone here familiar with these and have any suggestions?