I would pull the water supply underneath and see if that fills a bucket well.
If you have water there, then you can look at the faucet.
I have a Moen Extensa one handle faucet. The Extensa model is a pull out type faucet where you can pull out the sprayer (its an all in one deal).
After the water was shut off to our house, when the water was turned back on, the hot water is now much slower than the cold and slower than it used to be.
I took off the aerator and cleaned that, nothing of interest in it. Even with the aerator off, if you turn the handle from cold to hot you can see the dramatic difference in flow.
The following PDF at Moen pretty much describes my faucet. My faucet is one of the discontinued models from 5 years back or so, but the guts are still pretty much exactly the same as far as I know.
Like I said, even with the aerator off, the hot is definitely slower than the cold. It was fine before the water shutoff to the house and then after water was back on and the air and water shot through the lines it was slow.
The supply line for hot and cold are open all the way.
I'm wondering where I should check.
I've thought about shutting off the supply lines and taking the hot off, and cleaning the hot water braided hose and looking there?
There is a check valve and gasket/ring where the hose for the faucet attaches to the pull out sprayer. That's probably too far though isn't it? That check valve has a screen so I thought maybe that might have an issue, but I'd think at that point if it was clogged up both hot and cold would be slow?
Should I check the supply line itself and perhaps the cartridge?
I'm not terribly confident in how I get to that cartridge. It looks like I have to remove the Moen logo from the handle, then use an Allen wrench to get the handle off, and then from there I might be able to see the cartridge. I know I need a special tool to get that out.
Can the cartridge have the 'hot' part clogged with debris? Do you have to remove it to clean it?
Any ideas would be appreciated. This has been a great faucet and I imagine there is an easy fix, hopefully just finding some sediment or some water scale/mineral deposit that broke free from the initial turn on of the water.