You may be a professional plumber or the do-it-yourself type, replacing your own water heater. Perhaps you installed a drain pan or reused the existing pan. If you look closely at the drain pan, particularly where the drainpipe connects through the side (most pans) you'll see that the bottom of the drainpipe is above the bottom of the drain pan by about 3/4". In other words, if water should enter the pan, 3/4" of water will build up (retained water) in the pan before it starts to drain.
How often does water enter a drain pan? Probably more often then you think or are aware of. In most water districts it is not allowed, by way of a one way valve, for water to flow from the house back into the cities water supply for obvious sanitary reasons. When water is heated it expands and that excess water has got to go somewhere. Normally and with irregular frequency the pressure relief valve on the water heater will release excess water into the drain pan.
If you look around the bottom of your water heater and see rust even though there is no water in the pan at that moment, it very well could be from retained water that HAS been in the pan. This retained water at the least can rust the jacket and tank of the water heater and at most, as in the case of many gas water heaters, be a fire hazard or cause functional problems by blocking critical airways for combustion.
Also, many water heater installations are not on level surfaces. I have not found a quality, long term way to level a water heater other than the use of improvised shims or some other makeshift way.
Has anyone else recognized these problems? Have you experienced malfunctions caused by them? Any solutions?
Thank you, Chris
