Things You'll Need
An adjustable pipe wrench
A concentrated bottle of lime and scale remover
Hot water pipes are very susceptible to lime buildup. It's the same with hot-water heaters. The hot water dissolves lime, so that it flows freely with the water. However, the lime solidifies once it cools. That can be a problem for heaters and your hot-water pipes. You can increase your hot-water flow, however, and make your pipes more efficient.
Turn off your hot-water heater. If you have a gas water heater, turn off both the gas-feed and water lines. Otherwise, you can turn off just the water line.
Drain out half of your heater's water. Find the drain nozzle on your water heater, and adjust it so that the water drains out. If the floor under your heater does not have a drain, then you need to use a bucket to collect and dispose of it. Other hot-water heaters may take water out through pipes. Follow your specific model's instructions. Each make, model, and year of hot-water heater is slightly different, but nearly all have specific instructions mounted on them near the nozzle.
Remove the pressure valve. Generally, is it on top of the hot-water heater. Put on your gloves. Then, using your adjustable pipe wrench, turn the valve in a counter-clockwise rotation to remove it.
Pour the entire bottle of lime remover into the open valve.
Replace the pressure-release valve.
Restore the heater to normal operations. Turn on your water feed, and according to instructions on your unit, relight the hot-water heater. Allow the tank to fill up completely. You may hear bubbling and hissing, but that is normal.
Go through your house, and turn on the hot-water faucets. Hot water and foam will pour out of them. That is exactly what you want to see. That means the chemicals are removing lime and scale from both your hot-water heater and your water pipes. Keep the faucets on until the water runs clean and clear. Once you see clear water coming out, that means that your pipes, quite literally, are as good as new.
Do this on day when the weather allows for you to open your home's windows, as the lime remover may have a strong odor.
If you are living in a location in which there is a drought, keep in mind that you may violate water restrictions if you do this.