Grey smelly water from hot water heater.

[Tagkat]

I have an electic hot water heater in our vacation home. Sometimes we don't run the hot water for a few days. When we turn on the spigot's it smells like rotten eggs and has a grey/black tinge to the water. The hot water heater is a short tank. Could it be the anode? The heater is about 10 years old and I doubt if ever flushed. Is there a remedy?

Thanks!

 

[vaplumber]

I have an electic hot water heater in our vacation home. Sometimes we don't run the hot water for a few days. When we turn on the spigot's it smells like rotten eggs and has a grey/black tinge to the water. The hot water heater is a short tank. Could it be the anode? The heater is about 10 years old and I doubt if ever flushed. Is there a remedy?

Thanks!

I have been through this many times with summer homes here on the lake. First of all, drain the tank, remove the lower element and clean out the deposits as good as you can. It doesnt have to be perfect. Drain the tank at least twice a year, even if you only use it for a few weeks a year. When you leave the property, turn off the power to the tank. If possible, shut off the water and drain the tank. If this is not an option, when you return to the property, run the hot water tap long enough to empty half of the capacity of the water heater before restoring power to it. Yes this is caused by the annode in the tank. It is called hydrogen gass, and if you read the manual to the water heater, this gas is extremely flammable! This is normal, and may not be noticed on a new tank, but as the tank ages and the glass liner in the tank deteriorates, which is when the annode begins to do its job, this is when you will notice the odor.

 

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[Tagkat]

What about switching the anodes?

Somebody told me I could switch the anodes from magnesium to aluminum.

Would this work?

 

[Mikey]

Hydrogen by itself is odorless, colorless, etc., but in the right environment hydrogen sulfide can be formed -- that's the classic rotten egg odor. Here's a good Website from the Minnesota department of health that answers most questions: http://www.health.state.mn.us/divs/eh/wells/hydrosulfide.html

I replaced my magnesium anode with aluminum on Whirlpool's recommendation and the problem went away, but if you've got a bacteria problem it won't go away for very long. There are other magic anodes for sale that claim to do an even better job (Google {"anode rods"}). And, no matter what anode you use, periodic draining and cleaning (perhaps chlorinating as well) are required.

 

[vaplumber]

The sufide is a byproduct of the reaction between the annode and the metal tank. When the tank liner is in good shape, there is no reaction between the annode and the tank. The annode and the reaction to the water normally produces plain hydrogen gass, which is absorbed into the water and dispelled. It is when the tank liner is deteriorated that the sulfide is produced, and the gas no longer dissolves into the water. It is at this point that the loose gas and the rotten egg odor develops. This undissolved gas is like propane...flammable! You will notice small air bubble sounds if you barely crack a hot water tap. This is the undissolved gas. Keep the tank empty when you are not in the house, and it will be fine. The aluminum annode is a valid option, but will not protect the tank near as well. Steel (the tank) corrodes easily. Aluminum (the replaced annode) is not so easy to corrode. Therefore, the tank goes first! This is the reason for the original zinc/tin annode. Zinc/tin corrodes easier than steel, so the annode corrodes before the steel tank does.

 

[Gary Slusser]

The formula for the cause of a hot water only odor created in water heaters is as follows:

Sulfate is present in the water. A sulfate reducing bacteria is present in
the water. This bacteria takes the oxygen off of the sulfate, making it
sulfur.

The anode rod generates free hydrogen in water.

The hydrogen and sulfur together produces the smell. It is H2S (hydrogen sulfide) gas described as sulfur, rotten egg, sewer type odor.

Removing the anode rod will remove one part of the equation as long as you don't strip off some of it into the tank when removing it, eliminating the odor. Increasing the temp to 140f for an hour or so will kill the bacteria. Most water heater manufacturers also have a different type of anode rod available that does not generate the hydrogen - you would have to call them and see what is available.

Sanitizing the hot water heater with a heavy chlorine eliminates the
bacteria and produces a temporary relief.

To quote Wes McGowan, excerpt taken from Water Processing for Home, Farm and Business 1988:

When a hydrogen sulfide odor occurs in a treated water (softened or
filtered), when no H2S is detected in the raw water, it usually indicates the
presence of some form of sulfate-reducing bacteria in the system. These
anaerobic, single-cell bacteria (Thisbacilles) can exist in the piping system
in the home, especially on the hot water side. It is most noticeable on the
first hot water drawn in the morning. Sulfate bacteria can derive energy by reducing the sulfate ion in the water to H2S, and produce by-product bicarbonate in the process. Organic matter needs to be present for the bacteria to survive. However, the concentration of organics in the raw water is often below detectable levels. When this condition of H2S in hot water arises, the initial task is to heavily chlorinate the entire piping system including storage and hot water tanks. Usually, a dose of household bleach left standing in the piping system (hot and cold) over night will destroy the sulfur bacteria.