One other thing. If you are trying to get the fitting to unscrew, wrapping it with a strip of rubber or some gasket material is another way to get a grip on it either by hand or with a tool. In any case, good luck, and please report back on your progress.

We're not too experienced with this stuff so it may take some time. Thanks for the tips so far. We posted on the plumbing forum suggested.

Any chance you know the brand name of the fixture? That might lead you to an instruction page on the brand's website.

Sadly we don't know the name and haven't been able to find it on any site. We actually found the receipt from when we did a renovation in 1996 but all it said was "faucet".

Thank you so much for your help!

kudzu9 The lower part rotated counter-clockwise just as you suggested. Off to a plumbing supply place on Monday to get a replacement cartridge.

Great! :-) Always good to hear back that a hunch actually worked...

Update. My husband took the cartridge to a plumbing supply company and the person at the service desk was not able to identify it. They weren't busy and the person spent quite awhile searching through their catalogue. In his opinion some manufacturers deliberately don't put their stamp on their product or make it easy to replace the cartridge so you need to buy a whole new tap. We'll try another plumbing supply place but I'm not hopeful.

We're not confident in our ability to in stall a new tap so we'll need to get a plumber, in addition to the cost of a new tap.

Hope you find the replacement cartridge, but putting in a new faucet is usually pretty easy, and people here can explain how if you want to avoid paying a plumber to do this.

Any suggestions on a good faucet manufacture? Kohler and Moen? American Standard? I think I've heard bad things about Pfizer.

Kohler and Moen are generally reliable. I had a Moen kitchen faucet that developed a small drip after ten years, and they sent me a brand new identical replacement faucet for free even without a receipt as they have lifetime warranties on their products.

Delta. If something goes wrong you can call, tell them the problem and they will send what you need with instructions. No time limit.

There are many good manufacturers, but things can go wrong occasionally. The main point is to get a faucet from an established name brand that provides a lifetime warranty so that you can easily get a replacement product or part. That's why I stick with manufacturers that are U.S-based, have good tech support, and can provide parts quickly.

Delta here, too.

Update. I called the retailer back and this time I got someone more helpful. It's an Aquabrass and I bought the replacement cartridges. Thanks for your help and I'll keep your brand recommendations in mind the next time I'm shopping for plumbing.

Good luck. Check back in for help if you ever need to change out a faucet. ;-)