Hard Water, Water Softeners and Septic
Systems
Elizabeth Ward
In many parts of
the country groundwater contains high levels of dissolved minerals and is
commonly referred to as hard.
Groundwater very
slowly wears away at the rocks and minerals picking up small amounts of
minerals and metals that can be a nuisance in elevated concentrations, but in
small enough quantities improves the taste of water.
Calcium and
magnesium ions are the minerals that make water hard.
Water contains
traces of minerals that are essential for human health.
Though research has found conflicting results relating the mineral
content of water to the risk of cardiovascular disease, the majority of studies
indicate the lowest risk when minerals in water are highest and highest
cardiovascular risk when the water is soft.
Water containing
approximately 125 milligrams of calcium, and magnesium per liter of water (ppm)
or 7 grains per gallon can begin to have a noticeable impact and is considered
hard.
(Some label water
hard at 100 ppm.) Certainly, concentration of magnesium and calcium above 180
milligrams per liter (10.5 grains per gallon) is considered very hard.
As the mineral
level climbs, there are observed impacts in our homes. Bath soap combines with
the minerals and forms a pasty scum that accumulates on bathtubs and sinks.
The minerals also
combine with soap in the laundry, and the residue does not rinse well from
fabric, leaving clothes dull.
Hard water spots
appear on everything that is washed in and around the home from dishes and
silverware to the floor tiles and car (though commercial car washes use
recycled water and are more environmentally friendly).
Many can live with
the water spots and soap scum issues by adding vinegar to dishwashers and using
hard water formulated shampoos, but are induced to treat their water because of
the potential impacts on plumbing and appliances.
When heated,
calcium carbonate and magnesium carbonate are removed from the water and form a
scale (lime scale) in cookware, metal hot water pipes, dishwashers and water
heaters.
As the scale builds
up more energy is required to heat the water and hot water heater and
appliances have work harder which will burn them out eventually.
Thus, in hard water
locations hot water heaters and other appliances have a shorter life.
However, softened
water increases the potential for leaching heavy metal from pipes, solder, and
plumbing fixtures.
Increased levels of
copper, lead, zinc, and cadmium are found in soft water, particularly when it
stands overnight in the plumbing system.
The classic water
softening is an ion exchange system consisting of a mineral tank and a brine
tank. The water supply pipe is connected to the mineral tank so that water
coming into the house must pass through the tank before it can be used.
The mineral tank
holds small beads of resin that have a negative electrical charge. The calcium and
magnesium ions (along with small amounts of other minerals) are positively
charged and are attracted to the negatively charged beads.
This attraction
makes the minerals stick to the beads as the hard water passes through the
mineral tank. Sodium is often used to charge the resin beads.
As the water is
softened, the sodium ions are replaced and small quantities of sodium are
released into the softened water, thus the taste and potential health impacts
that requires bypassing the kitchen sink or additional treatment.
Eventually the
surfaces of the beads in the mineral tank become coated with the calcium and
magnesium. To clean the beads, a strong salt solution held in the brine tank is
flushed through the mineral tank this occurs two or three times a week and
consumes 20-30 gallons of water.
Sodium is typically
used in the brine tank, but potassium can also be used. The excess sodium
solution carrying the calcium and magnesium is typically flushed to the septic
system.
The amount of
sodium in water conditioning systems is a real problem for humans, the septic
system and the environment.
Softened water is
not recommended for watering plants, lawns, and gardens due to its sodium and
chlorine content. Water used in recharging a water softener is discharged into
the septic tank and soil absorption field if you have a septic system.
Otherwise a
separate holding tank or discharge, which could be emptied by a vacuum truck
would have to be installed into the plumbing system.
Salt water is
heavier than fresh water and interferes with the passive functioning of the
septic tank. The salt water sinks to the bottom of the tank occupying space
that is designed for the settling of heavier solids interfering with the proper
formation of layers in the tank and driving the solids and grease into the
drainfield.
In addition, while
some studies have shown that sodium does not interfere with bacterial action in
ATU tanks in alternative septic systems, David Pask, Senior Engineering
Scientist of the National Small Flows Clearinghouse has seen septic
distribution pipes plugged with a “noxious
fibrous mass” that was grease and cellulose from toilet paper that only
occurred in homes with water softening systems.
He felt the brine
in the conventional septic tank had interfered with the digestion of the
cellulose fibers and might be carried over into the septic systems drain field.
Field practitioners
reported to the Small Flows Clearinghouse negative impact from water softening
regeneration brines.
A study involving
two adjacent septic field dispersal systems in a shared mound have shown that
the trenches that received the septic effluent with water softener brine
discharges formed a thick, gelatinous slime layer that clogged the infiltrating
surface, while the trenches receiving no salt water discharge remained open
with a normal microbial clogging layer.
All of the salt
that is released into the septic system and ultimately the leach field and
groundwater can impact the ecology.
According to the U.
S. Environmental Protection Agency, chloride concentration above 180 mg/L
interferes with nitrogen fixation in the environment.
Chloride
concentration in the regeneration discharge can reach into the 10,000 mg/L and
sodium concentration can reach 6,000 mg/L.
According to Orenco
Systems a field study of 18 on-site wastewater treatment systems in Virginia
clearly showed that nitrogen removal was inhibited in systems receiving water
softener backwash brine.
To solve the taste
problem or health concerns associated with drinking softened water reverse
osmosis systems are often sold as an accessory item when a whole house water
softener is installed or for other actual or imagined problems without proper
testing.
Waste water from
household systems is typically connected to the house drains and will add to
the load on the household septic system.
This is a
significant additional water use and load to the septic system and could impact
the life and functioning of your septic system and well since a 5 gallon a day
reverse osmosis system might waste 90 gallons a day.
The principal uses
of reverse osmosis in are for the reduction of high levels of nitrate, lead,
mercury, arsenic, cadmium, sulfate, sodium and total dissolved solids.
No treatment is
without consequences and an inappropriate treatment could create other problems
without providing any measurable benefit.
Before considering
purchasing any treatment system test your water yourself to get a full picture
of the nature of your water supply.
Never purchase a
water treatment system without first fully testing your water for at least
iron, manganese, nitrate, lead, arsenic, fluoride, sulfate, pH, total dissolvedsolids, hardness, sodium, copper, total coliform bacteria and E. Coli bacteria,
appearance, taste and anything else of local concern.
Personally, I did
extensive water testing on my well before I purchased the home to ensure that I
could live with the well water without further treatment.
This does not
guarantee me a lifetime of problem free well water since groundwater is a dynamic
system that can vary over time and wells age and do die, but it is a start.
If you must soften
your water, potassium chloride can be used instead of sodium chloride in a
typical water softener.
Potassium chloride
works exactly the same way that sodium chloride does in the softening process
and the potassium chloride reduces the amount of sodium in drinking water, the
potassium in the treated water is a necessary mineral and it eliminates the
excess sodium in the septic system, drain field and released into the
environment, but not the chloride problem.
The impact of
potassium chloride on septic systems has not been studied. Potassium chloride
costs much more than sodium chloride. A forty pound bag of pellets costs about
$40 for Potassium chloride and under $8 for sodium chloride.
One final note,
though magnetic water softening is sold, according to research done at Purdue
University in the 1990’s this method of water conditioning was not
effective.
Mike R. Powell, P.E., author of an exhaustive discussion of the research
relating to magnetic water treatment entitled “Magnetic Water and Fuel Treatment: Myth, Magic, or Maintream Science?”
states “Much of the available laboratory
test data imply that magnetic water treatment devices are largely ineffective,
yet reports of positive results in industrial settings persist ….”
“Consumer Reports magazine tested a … magnetic water
treatment device…. Two electric water heaters were installed in the home of one
of the Consumer Reports staffers. The hard water (200 ppm) entering one of the
heaters was first passed through the magnetic treatment device. The second
water heater received untreated water. The water heaters were cut open after
more than two years and after more than 10,000 gallons of water were heated by
each heater. The tanks were found to contain the same quantity and texture of
scale. Consumer Reports concluded that the … unit was ineffective.”
I called Consumer
Reports to obtain a copy of the article and permission to cite it. The full 280
word article can be found in the February 1996 volume of Consumer Reports on
page 8.
It appears that
bottom line is, don’t waste your money on magnetic water treatment.
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Elizabeth Ward was awarded an
MBA from the University of Pittsburgh and an MS ChE from Polytechnic Institute
of NYU, worked as a chemical engineer for both the US EPA in DC, and at DuPont
before working in finance and then becoming consultant with Washington Advisors
and is the author of "The Lenders Guide to Developing an Environmental
Risk Management Program."
Elizabeth retired from
Washington Advisors and began her volunteer career and is currently the
Treasurer of the Prince William Soil and Water Conservation District.
http://greenrisks.blogspot.com/search/label/septic%20systems
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