Yes, you can use a metal water pipe that ties to the main water line exiting the building. While you may have a metal pipe in your kitchen the buildings water line might be plastic!
Clean off any paint or oxide build up where you plan to connect. You’ll likely want to get a heave gage Green colored wire (not bare wire) a pipe clamp to clamp the wire to on the pipe. Run the wire near an outlet carefully use a DVM set to measure voltage between each of the outlet connections (into the slot) and your ground wire. One of the slots should allow you to read off your buildings voltage (120/220 volts AC) the other slot may still have some voltage (10 volts or less) this is leakage. If you are getting more then some device in the building is sorted to ground. This is one of the risks with older two prong outlets as the polarity of the outlet may not be wired correctly or the device does not have a polarized plug!
FYI - You may want to find out what the regulations are for renting buildings which still have older two prog outlets. Some towns have requirements for renters. And we are not talking about just replacing the outlet and not connecting the ground leg.
Many hardware stores have Outlet Testers you may want to get one and a 3 prong to 2 prong adapter which is polarized that way you can make sure the wiring of your rental unit is properly wired (two wire are correctly polarized) and if you find a 3 prong outlet see if its wired to ground in some fashion (the work box its in maybe grounded, just missing the leg to the outlet).
Now the last part here is you’ll want to mount the free end of your wire in a plastic box with an RCA phono plug outlet so your strap can be connected to. If you have a mat take the lead it offers and attach a phono plug so you can plug it in. You want the ground wire isolated so it can’t be touched directly. Your mat wire and/or wrist strap have a resistor in them to protect you from electrical shock in case you are working on something live (not a good idea in any case). Lastly, many mats have a snap to attach the wrist strap so you only need one connection. I also recommend you take the time to test your ground connection to make sure something doesn’t get disconnected.
Common Point Ground Connection