The spout is rotted out, the minerals in the water react with the poor quality brass in the tap spout, and this etches out the metal, and creates pinholes in it. I have to replace our sink mixer every couple of years, it does the same thing.
You can't fix them, or buy parts for them, just buy a new sink mixer, they're only about $35 - and they're just about all made in China, we make only minimal amounts of tapware in Australia today.
You can buy Methven for lots more money, the Methven stuff is made in NZ, but the Methven stuff is horribly expensive. Phoenix, Brodware, Astra Walker, Faucet Strommen, and Sussex are made here, but are "exotic" in their pricing, too.
The Estilo, Mondella, Caroma, Dorf and a few other brands are all made overseas, in China and Malaysia. They have a warranty period of between 1 and 2 years.
I bought a Methven shower rose head with adjustable arm about 3 years ago, and the pipe on the arm rotted out, and developed pinholes, and sprayed all over the shower.
I pulled it off, and found it was made out of a cheap-arse really thin piece of brass pipe. Then I studied up and found out Methven have a lifetime warranty!
So I contacted the Methven agent here and told them my sob story, and sent them photos of the arm. In the best fashion, we'd lost the receipt - but I had the original box it came in, so I gave them photos of that, too.
They hummed and hah'ed, and said by law, a receipt is required to claim (which is correct). So they thought about it for about a month, then said they'd replace it, as an act of grace.
I waited about another 6 weeks, and was getting ready to contact them, when a parcel arrived. It contained a whole new shower arm, including the adjustable pivot ends (not just the pipe) - and this replacement unit was made out of a MASSIVE piece of brass, with the setup weighing about 2kgs!! I was amazed, and convinced they'd sent the wrong part. But I waited a week and heard nothing, so I thought I'd try fitting it up. It fitted perfectly to the old shower head, and looks a million dollars.
The stunning part is - we paid $117 for the original shower head and arm - but the same part number is still available at Bunnings, and it's now $265! They must have lost a lot of money on warranty claims and are now making up for it! I have to say, the new shower arm looks like it would last the average persons lifespan.