How do I fix the water flow in my tub/shower?

I recently replaced the faucet fixtures in my bathtub/shower. When I turn on the water full blast, I only get a trickle. I've checked the house water source as well as the water to hot/cold lines directly to the bathroom and they are all full on.

What did I do wrong?

Answers:
on the nozzle of your faucet, there is a ring holding a small screen on. loosen the ring, and check to see if the screen is clean. run the water a bit.

Other answers:
Take out the water filter. If that doesn't work replace with $10 showerhead. They work great.
Take out the water filter. If that doesn't work replace with $10 showerhead. They work great.
Check the supply line to the faucet immediately behind it. While tightening the brass bolt, your supply tube got kinked somehow. This is a common problem. You probably overtightened it.

If this is OK, then the washer need to be checked. It does not let the water out. Take out the washer and inspect. Repair or replace.

Check your showerhead. There is a filter assembly in there. Perhaps, you installed it the otherway around. Take it out and reverse the filter and refit. Before you do it, take out the shower head completely and turn on the water without the showerhead. If the flow is good, the showerhead is your culprit.

If this is a new faucet, and it of the washerless type, then you have ceramic cartridge. It may not be seated right. You must re insert it in to the faucet as per instructions. Because you say you just installed the faucet, I am assuming it is new. Otherwise, the cartridge is under warranty, get a replacement for free.
The problem is two fold. One it is probably a water saver disc in the shower head and the pressuse balance control in the mixing valve could be defective (ie small particle in line cause a lot of problems)
Are you getting low flow out of the tub faucet as well as the shower head? If the pressure to the tub faucet is fine and the shower head is only a trickle, the recent install may have caused sediment/corrosion to be jarred loose. You need to disassemble the shower head and check the sediment screen for blockage.
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