This is a common one. You purchase a home, you move in, everything is going along well and then… You notice… a peculiar (rotten egg) smell when you are taking a hot shower, or perhaps you begin to notice brown stains on your sink, toilet or even cloths. You have a water problem. Most people will call it sulfur water or something similar. Actually, the more likely culprit is iron.
Iron is the second most common element in the Earth’s crust. It can cause all sorts to problems with a domestic water supply. In some areas, iron in well water is endemic. The only solution is to filter it out before it gets into the house hold water system.
There are two types of iron that can be dissolved in water. Ferrous iron (Fe2) is noticeable because the water will be brownish yellow. It will stain almost anything it comes in contact with. Often times, brown silt will settle out of the water if allowed to stand. Ferric iron (Fe(OH)3) is a little harder to detect. It is a mineralized iron commonly found in soils that dissolves in water. It is non-oxidized until it comes in contact with air so the water will look clear for the most part. It can also stain surfaces although not as bad as ferrous iron. What these have in common are the bacteria that feed off of the iron.
As the bacteria feed off the iron they produce Hydrogen Sulfide (H2S) which is what produces the rotten egg smell. Hydrogen sulfide is slightly heavier than air, so it will settle into low places and can be explosive if allowed to build up to high level. Most often the iron eating bacteria live in the hot water heater, so the rotten egg smell will be very noticeable in the hot water.
A standard water softener will not adequately remove large concentrations iron from water. For domestic potable water, most recognized experts state that unprecipitated iron should be not more than 0.3 PPM. Water softeners will remove some iron if the concentrate is less than 5 PPM. For concentrations greater than 5 PPM a specialized iron filter system is needed.
There are a couple of different strategies for removing iron from water. The first is a “Greensand” filter. Greensand is actually Glauconite, a green clay mineral that contains iron and has ion exchange properties. This will trap the iron in the filter. Greensand filter require regular backwashing to rinse out the accumulation of iron. Most manufactures require at least 2 X per week, at about 50 gallons per backwash cycle. This may be a problem for wells that are low have low water production or recovery rates. Greensand filters work very well for Ferrous iron and moderately well for Ferric iron. Thanks to Jay G. for the picture of his green sand filter.
The next method is oxidation through chlorination then filtering. This is the method I chose, since my water iron seems to be ferric. A chemical feed pump injects the chlorine before a sand filer (different than a “greensand filter”). Sand filters are also called “clarifiers.” They filter out small particles suspending in the water. The chlorine oxidizes the ferric iron forming large enough particles for the sand filter to remove. This method requires a contact time of about 20 minutes so a blending tank is often required between the chemical feed pump injection point and the sand filter. Like the greensand filter, a sand filter needs to be backwashed regularly to rinse out the iron and other materials trapped in the sand. Chlorine also has the added benefit of killing germs. You need to adjust the chlorine injection pump to that there is enough chlorine to oxidize the iron without too much residual chlorine in the water after it is filtered.
You can check the residual chlorine levels with a swimming pool chlorine test kit. It should be no more than 0.03 ppm. Even this may lead to a chlorine taste in your drinking water. You can either filter the drinking water with an active carbon filter or let is stand for a few hours. I always put a pitcher of water in the refrigerator so it gets cold. With this system you have to monitor the amount of chlorine solution in the chemical tank and replace as needed.
Other water problems include “Hard Water” and acid water. Hard water is when a high amount of minerals such as calcium are dissolved in the water. If you have hard water it will be difficult to get soap to lather and a white crusty buildup of calcium will form on hot water appliances such as coffee makers and tea kettles. The minerals can be removed from the water supply using a water softener.
Acid water is common in the western part of the US. This water has a low PH which can cause plumbing problems, especially with softer metal pipes and fittings like brass or where copper pipes are jointed with soft metals like lead. Most homes over 25 to 30 years old have lead solder joints in there copper pipes. Pool supply houses have PH test strips, these are a convenient way to check the acidity of your water.
Acid water can be corrected by adding sodium bicarbonate (also known as baking soda) to your water supply. A chemical feed pump just like the one used to feed chlorine can be used to feed sodium bicarbonate into your water supply.
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