Low water pressure in the whole house can be caused by a number of factors, including:

1. Shut or blocked water meter valve: If the valve is shut or blocked, it can restrict the flow of water into your home.
2. Mineral buildup: Over time, minerals can build up in pipes and restrict water flow.
3. Corroded pipes: Corrosion can cause pipes to narrow and restrict water flow.
4. Crack in the main city supply pipe: A crack in the main city supply pipe can reduce water pressure throughout your home.
5. High demand for water usage: If multiple taps or appliances are being used at the same time, the water supply may be divided, causing a drop in water pressure.
6. Malfunctioning water softeners or home filtration systems: These can cause low water pressure.
7. Faulty fixtures: If all plumbing fixtures in the house have low water pressure, the issue may be with the fixtures themselves.
8. Faulty pressure regulators: If your plumbing is equipped with a pressure regulator, a malfunctioning regulator can cause low water pressure.
9. Closed or partially closed water valves: If a valve is accidentally left partially closed, it can restrict water flow.
10. Clogged water pipes: Clogs in pipes can restrict water flow and cause low water pressure.

If you are experiencing low water pressure in your home, it is best to contact a plumber to diagnose the cause and recommend a solution.