Pro Handyman Blog

Many people wonder if they need to replace the copper flex lines when installing a new water heater. My answer is probably not. As long as the copper flex lines are not damaged or corroded in some way, they should last for decades. Notice I said as long as they are not damaged or corroded. I have seen people twist these lines in an unnatural way that causes them to bend or kink. This is a problem because it can minimize the volume of water flowing through the pipes.

In the case of a temperature and pressure relief valve (TPR), minimizing the volume when the valve opens due to excessive heat or pressure can cause catastrophic damage (the tank could explode). So it is important that the copper flex lines have only gradual changes of direction.

So you likely won’t need to replace the water supply lines, but you should replace the washers inside the fittings at the end of these lines. They are inexpensive and will replace the nasty squashed washers that have sat in there for years. Dig out the old washer and simply push the new one into the fitting until it bottoms out against the back of the fitting. Then install the flex line to the water heater’s nipples.