Regularly, I receive questions about people’s wells through my blog. Recently I received the following question:
Our well water great then all of a sudden for the past month we get this smell from our water (only the hot water) and it leave an oily texture on our skin and also has this foul smell. We tried cleaning the hot water tank and that did nothing. Don't know what else to do!
Often there are limits to how helpful I can be to questioners because there is not enough information, but this sounds like hydrogen reducing bacteria have taken up residence in the hot water heater. There is an easy fix for this.
First a little background. Hydrogen Sulfide gas (H2S) with its characteristic “rotten egg” taste and smell can actually be detected as an off smell at 0.5 parts per million (ppm) by most people. At less than 1 ppm, hydrogen sulfide will give water a musty odor. At 1 to 2 ppm, it will have an odor similar to rotten eggs. Levels encountered in private wells are usually less than 10 ppm, because high levels of gas will not remain in solution in the water. Though toxic at 800 parts per million, Hydrogen sulfide is heavier than air and can accumulate in pits and basements and can potentially create a health and explosive hazard (though the smell might kill you first).
Hydrogen sulfide can end up in your tap water by four different routes. (1) It can occur naturally in groundwater especially in oil rich shale and coal seams. (2) It can be produced within the well or plumbing systems by sulfur reducing bacteria (bacteria that essentially eat sulfate in areas that have a high natural level of sulfate in the rocks. These anaerobic bacteria occur naturally in decaying plant material and soil and many areas in the nation have high natural levels of sulfate in the groundwater. (3) Hydrogen sulfide can form in hot water heater by either supplying a pleasant environment for the sulfate reducing bacteria to thrive or the energy for the magnesium rod intended to prevent corrosion of the heating tank to react with the sulfate naturally occurring in the water. (4) Finally, there are instances where the hydrogen sulfide gas is due to contamination of the well with septic waste.
Back to the problem at hand. Because hydrogen sulfate is so easily smelled by the typical human being, smell alone is enough to identify the problem. Also the description of the water as feeling oily is enough to identify the sulfur reducing bacteria. These are the classic symptoms of sulfur reducing bacteria creating hydrogen sulfate in the hot water heater. Though, I would have describe the feel of the water as slimy (after all I know what’s in it), the questioner’s description is classic for this problem.
If the smell is only from the hot water faucet and not from the cold water, then the problem is in the hot water heater. It is either sulfate reacting with the magnesium anode rod, or sulfur reducing bacteria (flourishing) in the hot water tank. The description of the water as oily would indicate the problem is sulfur reducing bacteria flourishing in the hot water heater. The reason that cleaning the hot water tank did not work is that the reducing bacteria were probably originating in the well and the water has naturally high levels of sulfur.
There is no standard test for sulfur reducing bacteria, so without the feel of oil it is often difficult to differentiate between a bacteria problem and something that might be solely sulfate reacting with the magnesium rod in the tank beyond the feel of the water. Also, hard water and certain soaps can leave a residue easily confused with the feel of reducing bacteria in the water. Thus, it is generally best to treat the hot water tank for both sulfate reducing bacteria and for the magnesium rod reacting with the sulfate naturally occurring in the water. It is a good idea to chlorine shock the hot water heater to kill the bacteria then flush it. But first start by raising the temperature in the hot water heater to 160 degrees Fahrenheit for three hours or more. This will generally kill the sulfur reducing bacteria. Hot water tanks use a lot of energy to keep the water hot, and we have all been advised to lower the temperature on the tank to 140 degrees Fahrenheit to save energy. Unfortunately, that is a temperature at which reducing bacteria thrive. So, pump the heat all the way up and kill the bacteria.
At this point you might want to flush the hot water heater a couple of times and let it heat back up and see if the problem is gone. Even if this works, the cure probably won’t last. It is likely that the iron bacteria are being introduced from the well, but keeping your hot water heater at 160 degrees will constantly kill the bacteria. If you do not want to keep your hot water heater set so high, then move on to disinfecting the hot water heater and replacing the anode rod and know that you will have to regularly disinfect the hot water tank. I dealt with a similar problem by disinfecting the hot water tank then simply keeping the hot water very hot. I bought an insulated cover for the tank to cut down on the power usage.
It is not very hard to disinfect a hot water tank, but unless you are very familiar with operations and maintenance of hot water heaters, you should call a plumber. Either turn off the hot water heater if it is electric or put it on pilot if it is gas and drain off a few gallons of water after you close the cold-water inlet valve. Make sure that you have drained off at least a few gallons and pour a half gallon of household bleach (5.25% hypochlorite) mixed with water into the tank. The best way to get the bleach into the tank is to use a funnel and either the temperature and pressure valve opening, anode rod opening, or hot water outlet pipe opening to pour the chlorine into the hot water heater. Let the chlorine sit in the tank for at least two hours. Then open the cold-water inlet valve, drain the hot water heater and turn the heat back up. If the problem is sulfate reacting with the magnesium anode (corrosion protection rod), it can be replaced with an aluminum rod that is not as reactive as the magnesium and may still serve to protect the metal components of the tank from corrosion. Most hot water tanks take a standard size anode rod and there are aluminum replacements available from several manufacturers. Generally, you should check the condition of the anode rod when you pour the bleach into the tank. Be aware that some high end tanks have two anode rods and replacing just one with aluminum will not solve the problem because the remaining magnesium rod will continue to react with the sulfate.
For instructions on how to identify the source of your hydrogen sulfate problem and solve it see Hydrogen Sulfide-the Rotten Egg Smell in Well Water.