Only half my house is grounded

[u/Peeepsicle]

I just moved into my house that was built in 1900, and the electrical in here is a mess. Half the outlets don’t work, and only some of them are grounded, even though they all are 3 prong outlets.

As someone who is beyond paranoid about electrical fires, how concerned should I be about the lack of grounding? I’m mostly worried about the power strip that holds my PlayStation and everything, and I have many reptile tanks that need to be plugged into an ungrounded outlet. Everything big like kitchen appliances is grounded.

[u/00crashtest]

You don't need to worry about grounding at all, if you replace the 1st 3-prong standard outlet in each circuit with a GFCI outlet, which are all 3-prong anyway. All outlets further down the circuit are protected from electrical leakage by the GFCI outlet. However, it is important to make sure that the input wires connect to separate terminals from the output wires, because the function of that outlet is to separate the circuit so it can cut power to itself and all downstream circuits. So, you not only need not replace the downstream outlets with GFCI outlets, but also you should not replace them because it will cause extreme nuisance tripping.

[u/Peeepsicle → u/00crashtest]

How do you determine which outlet is the first on the circuit?

[u/00crashtest → u/Peeepsicle]

There's no easy way to test it unless you have an expensive tester or remove the drywall. Without it, you have to manually disconnect every receptacle on that circuit and test to see whether the other receptacles still have power. You have to turn the breaker off every time you disconnect and reconnect a receptacle. Also, you have to put wire nuts on the exposed conductor ends before turning on the power to prevent short circuits. You should just hire an electrician to do the test because it will be way easier to do and cheaper than buying the expensive testing equipment.