Do not, I repeat, DO NOT ever put a drop of the local water in your mouth unless it comes in a bottle. The water in Jakarta is incredibly polluted. OK, I learnt this the hard way. I thought that the tap water in the hotel would be safe enough to brush my teeth with. Somehow, I never made the connection between using tap water to brush my teeth with the tummy upsets I was getting. So I'm a bit stupid sometimes. :))
If you are not local, you are likely to have problems with the local water. I was lucky enough to escape with just minor tummy upsets. Dear Hubby used to come home to KL from his Jakarta trips 4lbs lighter and looking sick as a dog. You can shower in it as long as you keep your mouth shut and do not sing in the shower, but do not brush your teeth with it, do not wash your vegetables with it and do not drink it unless you fancy colonic cleansing on a major scale.
Houses and hotels are all equipped with a water cooler and water vendors sell the 15lt bottles everywhere for those coolers and that's the water you use for drinking, washing and brushing. If you're thirsty, get yourself a bottle of water, it's very cheap. I paid Rp1,000 (30 sen) for a small bottle of water that would normally cost me RM1.20 back home.
I can't believe I'll have to put up with this for next few years!