Q: Why is the cold water inlet pipe on my water heater hot up to five feet away?
Thanks in advance! — Jan O.
A: It is normal for the incoming cold water pipe to get a little warm due to convection – that is, hot water rising in the tank. Also copper piping is a good conductor of heat. Many modern water heaters have built-in heat traps to limit the migration of hot water.
However, hot water five feet back on the supply line is not normal. There are a few possibilities:
- The installer used a torch too close to the top of the water heater when installing it and damaged internal components. For example, there could be a hole in the dip tube, which supplies hot water to the bottom of the tank.
- There is cross-contamination between hot and cold lines. For example, this can happen in a washing machine or a shower valve.
A check valve can be installed with an expansion tank between the water heater and check valve, but this is rarely done unless you have a water softener nearby or a recirculating hot-water system (to provide instant hot water to distant fixtures in a large home).
An improperly installed or malfunctioning thermostatic mixing valve could also be a factor. This is a whole-house anti-scald system that allow you to keep the water heater set very high – around 140 degrees F, while delivering hot water to fixtures at 120 degrees.
Many people, myself included, just set their water heaters at a lower temperature – around 120 degrees to protect against scalding and save energy. The lower the temperature of the storer water, the less the heat loss. Some experts are concerned that this introduces a risk of Legionnaire’s Disease brewing in your water heater, but it’s not something I worry about.
You can also have your plumber install external heat traps in your piping entering and exiting the water heater. This is simply an inverted “U” in the inlet and outlet pipes that keep the hot water from migrating (see diagram). Insulating the hot sections of pipe is also a good way to prevent heat loss.
First thing, however, it to have a licensed master plumber take a look and figure out what is causing the problem. — Steve Bliss, Editor, BuildingAdvisor.com