Post date: Jan 12, 2015 2:59:07 AM
According to the Culligan Man the water in Taos is ‘extremely hard’, specifically 15-20 grains per gallon. A grain is 64.8 milligrams, so this translates to 225 to 340 parts per million of Calcium Carbonate equivalent. (Some of the hardness is due to Magnesium Carbonate.)
There are these types of water softeners that actually work:
The chelation type of water softener gets mixed user reviews. Most of the bad reviews are from folks who expect the wrong result (like filtering out sulfide smell). Chelation can work. (I have a master’s degree in inorganic chemistry, so I can understand the explanations.) Since calcium and magnesium (the primary culprits) are metals, chelation should trap the metal ions in an organic ring. From wikipedia:
In earth science, chemical weathering is attributed to organic chelating agents (e.g., peptides and sugars) that extract metal ions from minerals and rocks.[9] Most metal complexes in the environment and in nature are bound in some form of chelate ring (e.g., with a humic acid or a protein). Thus, metal chelates are relevant to the mobilization of metals in the soil, the uptake and the accumulation of metals into plants and microorganisms.
Polyphosphates work well as chelating agents, especially in alkaline water (which we have in Taos). Many polyphosphates can accomplish the desired effect at levels far below that which would seem to be required for a stoichiometric (molar equivalent) reaction. For example, water containing 200 parts per million (ppm) hardness (as calcium carbonate, or CaCO3) would theoretically require about 500 ppm of SHMP to sequester the available calcium. Actually, only 2-4 ppm of SHMP (Sodium hexametaphosphate) is typically used to inhibit scale formation. This "threshold effect" of SHMP apparently occurs by interfering with early crystal growth.
The chelating agents in the softener must be replaced periodically, as they are used to trap the metals, then go into the sewer. Most chelating systems are sold as and with water filters, sometimes both before and after chelation.
Another technique that works is an ion-exchange resin, usually a zeolite, that holds sodium ions or an acid (proton) on the large surface of the resin (not chemically combined) and trades these for the heavier calcium and magnesium ions. The resins have to be recharged by flushing with a salt (either sodium or potassium chloride). This process generally adds a very small amount of sodium to the diet, but that doesn’t bother me. (Proton recharging with acid is less common.) Ion-exchange systems generally do not include a filter.
So both techniques will help. People’s reactions (as expressed in customer reviews) are often very subjective. It takes a lot of sleuthing and interpretation to determine what is happening objectively. Scum, toilet rings, and hazy film do seem to be reduced by the chelation devices as well as the ion-exchange devices.
Comparison of Models
A list of water softeners that do not use salt (eg, not ion-exchange) is found on this site: SaltlessWater.com.
For purposes of comparison, here are my estimates of water use from my blog:
City water use assumptions, per person:
Eliminate the toilet (as not being softened) we have a monthly total soft water use of 680 gallons per person per month. Assuming 12 grains per gallon, we would need to remove a little over 8,000 grains per month. If I am softening water I can measure the amount of calcium and magnesium ions (‘hardness’) in the water system. I want to know how much it will cost to remove a given amount of ‘hardness’.
Aquasana
Aquasana makes three sizes (for whole house) of filters, rated as 3-, 6-, and 10-years. There is no clue what their capacity might be, as they are rated in years. This may be good marketing but, of course, is nonsense. The ‘test results’ they provide indicates the removal when new, but not the life of a cartridge.
Their explanation only applies to true filters, which cannot remove hardness because the calcium bicarbonate is dissolved and not particulate.
20,000 grain 20 in. uses polyphosphate beads to “alter the charge” of the metal ions (which is impossible). However, it appears that polyphosphates are a chelating agent, which, of course, gets used up as water flows through the filter (regardless of the hardness of that water).
New Cost: $1500
Operating cost: replace every 6 years, so $250/year
Pelican
Pelican claims they make the hardness precipitate out of the water by releasing small crystals of Calcium Carbonate into the water, which act as seed crystals to cause the hardness to precipitate. This would only happen if the solution of ‘hardness’ were supersaturated because the carbonic acid that dissolved the carbonate is gone (which does happen with heating).
They claim that by forming small (micro) crystals of calcium carbonate that remain suspended in the water, the crystals will not build up on metal surfaces such as water heaters. Pelican chooses a crystal structure (there are several possibilities) and allows these to be carried into the water stream in suspension. These seeds grow, taking the calcium out of solution before the calcium can precipitate (form crystals) on the surface of the water heater (for example).
Among all the sales jargon, this explanation makes sense to me as a chemist.
New Cost: $800
Operating cost: cannot be determined from the available data. :(
NuvoH2O
These folks use citric acid (?) to raise the pH (acidity) of the water and chelate the calcium ions with citrates (which are known to be chelating agents).
They rate their systems by house size (square feet), but the house size is rated for 35,000 gallons and the cartridge costs $70. The active citrates are released into the water regardless of how much or little hardness is present. So the operating cost will be $2/1,000 gallons of water.
New Cost $650
Cartridge $70 for 50 months or $16/year
Ion Exchange
40,000 grain ion exchange resin
GE Model # GXSH40V (but there are many similar)
New Cost $600
Recharge cost 8,000 grains/month - recharge every 5 months for $10 in NaCl or $24/year.
Abundant Flow Water
Ion Exchange. Model 32k-AFW1, 32000 grain capacity, automatic recharge
New Cost : $700
Salt: $15/year
Scale Sentry
New Cost: $1000
Replacement media (after 10 years) $170/liter (more than one required?) if one, then $17/year
Aquios AQFS220
New Cost: $500 with filter
Polyphosphate Cartridge (40,000 gallons) $60 lasts 58 months so about $12/year.
Culligan
Culligan will sell me a pre-filter and ion-exchange softener for about $2500, which automatically recharges. Salt purchase same as above. They like to sell reverse osmosis after the softener to remove the sodium - but that is not really necessary.