Before your water heater goes out, it will try to give you signs to let you know that it is reaching the end of its life. The key is to pay attention to the signs that your water heater gives you before it goes out.
#1 Discolored Water
When your water heater starts to fail, one of the most obvious signs is discolored water. When your water heater starts to reach the end of its life, the water that comes out of your faucets may have a brown look to it. This brown tint is generally caused by rust. It may be hard to see this when the water is running, but if you put some water in a cup, you should be able to more clearly see the discoloration in the water. This happens when your tank starts to rust from the inside out.
#2 Sediment in Water
Another sign your water heater is starting to fail is sediment in the water. When your water tank starts to fail, more sediment will build up inside of your tank. You may notice more sediment in the water if you put the water in the glass. You can drain sediment out of your water tank. However, if you have to constantly drain sediment out of your hot water tank, that means that your water tank is failing. It is natural to drain sediment out of your water tank on at least a yearly basis. Draining sediment out of your tank multiple times a year though means that your water heater is no longer filtering the water properly.
#3 Metallic Taste
The way your water tastes is another sign of the overall condition of your water heater. Your water should taste clean and refreshing. It should not have a metal taste to it. Your water will get a metal taste from your water heater breaking down. The metallic taste will not harm you in the short term, however, you don't want to keep drinking off-tasting water for too long. You may be able to get a little more use out of your water heater, but it is not going to last that much longer.
When your water starts to look discolored, has sediment in it or develops a strange metallic taste, your water heater is letting you know that it is getting ready to go out. Start filtering your water and start looking for a new water heater.