How do you know it's Iron? Have you had the water analyzed? There's Arsenic Chromium lead... contaminates. Normally Chromium is found in well water but not at high levels.

Most people would have just bought the carbon faucet filter first, that's only common sense. If that doesn't work then move on to something more sophisticated. I have an RO system that works fantastic but I discovered years ago that it makes the water acidic. Cancer thrives under acidic conditions which is not ideal, so I moved onto a Water alkalizer. They have some really good filters that cost about $75 & give you healthy water. Only problem is you need to use it everyday or the filter will sour. So you couldn't leave it out there.

boil it first before using

I have small cabin in the San Diego Mountains which has a lot of iron-rich clay soil. Our 300ft well has always brought up water with a metallic taste and I know that the taste is a result of ferric or possibly ferrous iron meaning its dissolved until it reaches air where it becomes oxidized (ie: out of the hose it becomes yellowish). Im pretty sure sediment filters are too coarse for this dissolved iron. This is causing the taste but after hours of research, I only find that companies just say to use their $2000 greensand whole house filters. this cabin has one sink so there is no way in hell ill use that. Some say carbon filters work others say no.

Are there any small (cartridge filters) that I can use to remove this taste for the sink faucet? Or is reverse osmosis my only option?

Thanks!