Last night I opened the cold water on my faucet to fill a pot to make some ramen. Right as I was about to put my pot under the faucet the water turned brown and there was a noticeable pressure drop so I turned the faucet off.
Remembering a similar biyearly occurrence at a previous residence (every time they'd flush/check the fire hydrants), I assumed it might be rust that had clogged the airator screen. I removed the handle off of my faucet head and started to flush water into the sink. The water was clearer than before but it was still darker color than normal. After about 2 min it started looking more normal, then suddenly started expelling the large chunks, some as long as 4 cm pictured below.
Does anyone know what these are? Was this created by bacteria? rusting pipes? lime scale?
I called my utility to ask what was happening, they told me there was no work in my area, or hydrants being flushed and to just flush from the lowest point in my house. I did that but only saw a couple flakes which could of just been Teflon threading from the removal of the shower handle there. I went back up stairs to finish flushing my kitchen sink, but it took more than 20 min of shutting off and turning back on my cold water for the flakes to subside.
Best Answer
My best guess is limescale that's been knocked free by some kind of work upstream. You could contact your local water authority to see if you might have been affected.
You're right to clean the aerator screens in your faucets, etc. The only other thing you might consider (after running water for quite a while until it turns up clear) is operating all the shutoffs in the house. Open and close them a few times.
(Pro-tip: know where your main shutoff is and know that it works before you mess with the local shutoffs.)
Operating the shutoffs might chew up the washers and prevent the shutoff from working, so be prepared for this possibility. I mention this step because I'm of the 'it's better to know now and fix it, rather than when it's an emergency and you have water pouring into the sink cabinet' school of thought.