In Warrenton a Smell in His Hot Water

We went to Warrenton to drop off some very late gifts and visit with some relatives including  our nephew and get a glimpse of his new house. It is a really nice house still undergoing customization by him. He happened to mention that his hot water has a sometimes faint smell of rotten eggs. The symptom he described is typical of well water not so much surface water, and the house is on Warrenton “town water.”  So, I checked and it turns out that Warrenton uses both wells and the reservoir for source water. Only one of the town wells is treated with chlorine-That makes sense with his complaint.

Hydrogen Sulfide gas (H2S) gives water that awful “rotten egg” taste and smell and can be a fairly common occurrence in parts of the country, like around here where the groundwater is naturally high in sulfate. This problem can be solved, but let’s back up and start at the beginning. You have to first have sulfate present to have hydrogen sulfide (though a “faint smell” has sometimes been associated with iron bacteria).  Hydrogen sulfide naturally occurs in shale, sandstone, and near coal or oil fields, but can also be created by sulfur reducing bacteria “eating” the sulfate. According to the EPA, sulfur-reducing bacteria pose no known health risks. Sulfur-reducing bacteria live in oxygen-deficient environments such as deep wells, plumbing systems, water softeners, and water heaters.  Sulfate reduction can occur over a wide range of pH, pressure, temperature, and salinity conditions and produce the rotten egg smell and the blackening of water and sediment by the formation of iron sulfide if iron is also present in the groundwater or plumbing system. 

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 wells are usually less than 10 ppm, because high levels of gas will not remain in solution in the water. Though toxic and potentially lethal at 800 parts per million after 5 minutes of exposure, the Occupation Safety and Health Administration, OSHA, OSHA has established 10 ppm (20 times the concentration that you can smell it at) as the safe limit. 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 be corrosive to metals such as iron, steel, copper, and brass, and it can cause yellow or black stains on kitchen and bathroom fixtures, but the big problem is the smell, the water is undrinkable and unpleasant with that smell. Some water treatment systems can actually create the problem within the plumbing system. Most hydrogen sulfide problems can be solved if the correct solution is implemented. So if you smell Hydrogen sulfide in your water you need to figure out what is going on to correctly identify a solution.

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. It is only guessed at how the bacteria enter the well or plumbing system, but the DEQ in recent studies of wells has found these bacteria in all older wells. (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. Since this instance is public water that is extremely unlikely.

Because hydrogen sulfate is so easily smelled by the typical human being, just this one time, that is all you need to identify the problem.  If the smell is only from the hot water faucet as reported by our nephew and not from the cold water or the hoses, 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. 

Unless you are very familiar with operations and maintenance of hot water heaters, you should call a plumber. There is no standard test for sulfur reducing bacteria, so it is difficult to differentiate between a bacteria problem and something that might be solely sulfate reacting with the magnesium. You might  need to treat the hot water tank for both situations, but I suggested my nephew start with the assuming that bacteria took up residence in the hot water heater before he moved in. In that case the first thing to do is kill off the bacteria then flush the hot water tank. The easiest thing is to start by raising the temperature in the hot water heater to 160 degrees Fahrenheit for three hours. This will generally kill the sulfur reducing bacteria and all other bacteria. At this point you might want to flush the hot water heater a couple of times and let it refill and heat back up and see if the problem is gone. This cure probably won’t last, if iron bacteria are being reintroduced from the water system, but keeping your hot water heater above 150 degrees will constantly kill the reducing bacteria. If you do not want to keep your hot water heater set so high, then move on to disinfecting the hot water heater by chlorine shocking and replacing the anode rod.

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 a gallon or so and pour a half gallon of household bleach (5.25% hypochlorite) into the tank. Use either the temperature and pressure valve, 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.  

As a side note, according to recent research, increase salinization and resulting source water contamination has widespread implications for corrosion of drinking water infrastructure, including chloride acceleration of galvanic corrosion of water infrastructure and other premature plumbing  failures. Chloride can corrode and rupture hot water heaters.  Chloride potentially enhances hydrogen gas production which is explosive at higher levels, but at low levels also be food for bacteria – Harmless and smelly H2 S and far more serious Legionella. Warrenton does use a water softener (which adds sodium chloride) to control the elevated radium on one of the town’s wells, so that is a potential source of the problem.