There are a few discrepancies regarding the temperature setting of a water heater.  The Illinois state plumbing code requires that the maximum temperature produced from a tub and shower valve is 115 degrees Fahrenheit.  This law is in place to prevent being scalded by hot water.  There are three ways to solve this problem.  First, you can lower the temperature of the water heater to 115oF.  This can cause a number of problems:

1.    Every one-degree change in temperature equates to a 1% change in capacity.  For example, if you dropped your water heater temperature from 130oF to 115oF, you just lost about 15% of the heater’s capacity.  This could result in running out of hot water.

2.    Operating a water heater with a storage temperature below 115oF increases the condensation on the outside of the water heater tank.  This can result in premature tank failure.

Second, you can install a thermostatic tub and shower valve that will regulate the outlet temperature from the valve.  The problem with this solution is that it does not address the water temperature out of the other faucets in the house.

Finally, you can install a tempering valve onto the outlet of the water heater.  A tempering valve mixes, or tempers, the hot outlet water from the water heater with cold water to make sure that the all of the faucets and fixtures in the house will receive water of a safe temperature.  The tempering valve outlet temperature can be changed as the homeowner desires.  The cost of this safety device including installation should range between $400 and $800.00 depending on the size of the valve required and the existing piping configuration.

Should you have any questions about hot water, call David Ariano at Ravinia Plumbing & Heating at (847) 432-5561, e-mail at [email protected] or visit us at