Just bought a house. When using more than one anything in the house, the water pressure drops significantly. For exmaple: flush the toilet. While it's filling back up, the sink will just trickle water out. This is true for any 2 combinations of shower/faucet/toilet/washing machine in the house (basically anything that uses water). Doesn't even have to be in the same proximity to each other.
If using only one thing, the pressure is fine. I bought a pressure tester and hooked it up to the outside hose and it shows as 58, which from what I've read is normal.
This is a 2-story house if that matters.
Edit: Pictures
Best Answer
I would look at your pressure regulator. The device between the meter and check valve. Since it sounds like your pressure is good it could be debris built up limiting the flow. I have worked on many homes with 1/2" plumbing and a toilet should not take a sink to a trickle in fact 2 sinks open should not affect each other as the orifices in the valves are much smaller so I would look to find what is limiting the flow and in my experiance this has been debris built up at restriction points.