Just that fixture gave brown water?? not all the house water?

With a well system, there can be water that gets turned up a bit, but that should affect all the house water.

If you don't use the bathroom and the water sits in the pipes, I guess you could just have some sediment that settles...

Did it clear quickly?

pepperidge_farm, Yes, I think that one faucet is the only one I have noticed so far. I do use the sinks and shower in that bathroom and have not noticed any brown color.

But just to again clarify, it is hot, cold or both temperature water? Is it immediate, or did it turn brown after a few moments?

Well, by process of elimination you can narrow it down: it's not the whole house, nor is it all the fixtures to that bathroom. That leaves the pipes that supply the the tub.

What kind of pipes?
Copper? Any old copper? is the well water very acidic?

The whole house filter, is it just a sediment filter, water softener? If just a sediment filter, that won't eliminate dissolved iron, for instance...

I would also check another bath faucet, if you have more than one bath, or fill a large glass pitcher or even a big glass with the water and look closely. We're on a community well system and often when the water is being disgusting, it's obviously brown in the bath, but not so obvious in the sink faucets because of the lower flow, until you get a look at a clear vessel filled with the water.

Thank you all for your help. The plumber came out here today and of course the water was not brown this time. He said since I am not using it all the time, that could be the reason. It is a new construction house, so the copper pipes are new. I don't know if it came on with the hot or cold water when I turned it on yesterday.

Thank you!

We've lived in our house for 27 years. We're in the country and on a community well system. We've had everything from slightly tinged (brown) water to water so muddy you refused to bath it it :( I've had more clothes ruined than I care to think about. If the water is just slightly tinged with brown, I can tell you from experience that the only way you'll really notice it it is when it's in something white...white tub, white toilet, etc. Depending on how discolored the water is, it might look fine coming out of the tap or in a black or silver pot, but start filling up a white tub and you'll see it. In a toilet, you'll see discoloration at and below the water line. They may have had a small break in the line and this would be normal till the system is flushed. And it might be something totally different (g) That's just my experience for 27 years. It IS better now that we have a new operator that actually cares about our water quality.
Monica

They could have used an iron nipple for the tub filler. It should be brass. If water stands in an iron fitting, it rusts. But if it runs brown for more than a few seconds, it's something else.
Casey