Thursday, February 23, 2012
Corrosive Water- VAMWON Notes From the Field
VAMWON Notes from the Field are the water/ well problems I’ve encountered as a volunteer with the Virginia Master Well Owner Network (VAMWON), an organization of trained volunteers and extension agents dedicated to promoting the proper construction, maintenance, and management of private water systems (wells, springs, and cisterns) in Virginia. The Cooperative Extension Services in Virginia manages the program and has publications and fact sheets that can help homeowners make educated decisions about their drinking water. The VAMWON volunteer or Agent can help you identify problems with the water system and provide information on suggested treatments options and other solutions. You can find your VAMWON volunteer neighbor through this link by entering your county in the search box.
I was contacted by a homeowner who had his water tested by a water company and wanted to know if his water was safe to drink without treatment. He reported the results to me as follows:
Hardness - 3 gpg
pH - 6
CO2 - 40 ppm
The tests performed did not test for bacteria, chemical contaminants, only for pH and hardness. From that information there was no way to know if the well water was in fact safe to drink. The test was free and offered by water treatment companies that were trying to sell him water treatment systems so it only performed an inexpensive test for pH, derived CO2 and hardness- characteristics they could sell water treatment systems to address.
Water hardness is usually measured by adding up the concentrations of calcium, magnesium and converting this value to an equivalent concentration of calcium carbonate (CaCO3) in milligrams per liter (mg/L) of water. However, it can also be measured in grains per gallon. Water with a hardness of 3 gpg is equivalent to 51 mg/L . This water was soft and required no treatment.
Many characteristics of water actually determine its corrosivity including pH, calcium concentration, hardness, dissolved solids content and temperature. Water that is soft and acidic tends to be more corrosive, but water corrosivity is usually measured by saturation indices. Water with a pH lower than 6.5 is commonly called corrosive or aggressive water by water treatment sales people, which simply means it is slightly acidic. While consuming corrosive or aggressive water is not in itself dangerous, consuming some of the contaminants that may be dissolved from metal plumbing by corrosive water may pose health risks, particularly metals like copper and lead. That concern is mitigated if the household plumbing is PVC rather than metal piping. Corrosive water can also shorten the life of hot water heaters, washing machines and dishwashers. The pH scale is logarithmic. This means that water that has a pH of 6.0 is 10 times more acidic than water with a pH of 7.0, nonetheless, the water with a pH of 6 is about as acidic as a latte from Starbucks. It is not necessary to treat slightly acidic water if household piping is PVC, but treatment can be done simply with an acid neutralizing filter.
It is possible to measure CO2 directly in water using a TOC carbon analyzer. The injected sample is acidified to purge all of the CO2, which is then measured on an IRGA - infrared gas analyzer-detector. It is very unlikely that the fee test offered by a water treatment company used that level of analysis. H2CO3 and dissolved CO2 are in equilibrium with each other. Typically CO2 is a derived value using the pH measured at the tap. There is no drinking water standard for dissolved CO2, typically dissolved oxygen and CO2 content are of concern for ecosystem balance in surface waters. Ground water typically has CO2 concentrations under 50 ppm and I believe the derived measurement was given because CO2 has lots of “buzz” around it.
The calcite and calcite-blend filters used to neutralize corrosive water in homes work by adding calcium to the water, and will increase the calcium carbonate, hardness, of the water, making the water 'harder'. However, most acidic well water is soft to begin with, and after passing through the neutralizing filter it will be harder, but usually not hard enough to warrant a water softener. Generally, if the water is less than 170 mg/L or 10 grains per gallon, the water does not need softening. His water was 3 grains/gallon to begin with, after the neutralizer it would be expected to be 5 to 7 grains per gallon, as neutralizers typically add 3 - 4 grains per gallon on average. His water should still be well below what is considered “hard” and should not present any significant problems. Hard water can cause spotting and lime scale buildup in appliances shortening the life of hot water heaters, dishwashers and washing machines.
Acid-neutralizing filters consist of a corrosion-resistant tank filled with calcite (calcium carbonate in the form of limestone or marble chips) or a mixture of calcite and magnesium oxide (also called corosex). Neutralizer filters cost under $1,000 for homes with 3-5 bathrooms (installation is extra). Once you install a water treatment system, it must be maintained properly. Frequent maintenance is required for neutralizing filters. The tank must be routinely refilled with neutralizing material as it is dissolved. The rate of refilling can range from weeks to months depending on the raw water corrosivity, water use, and the type of neutralizing material. Backwashing is recommended to remove trapped particles that can promote bacterial growth and oxidized metals unless a sediment filter is installed ahead of the unit then of course the sediment filter will require maintenance. Always consider carefully if you should be treating your water before you start buying and installing water treatment systems.
A drinking water well that is contaminated could significantly impact your health and the value of your property. There is no requirement to test private drinking water wells for all the primary and secondary contaminants of concern to the US EPA under the Safe Drinking Water Act. The local health departments have local rules and regulations for the installation of wells and initial testing of the water for bacteria, but as the well owner you will need to take the initiative and test your water to make sure it is safe to drink. None of the testing done so far on this well would have tested if the water was safe to drink. Though there are many potential contaminants to groundwater that can impact your health, the Virginia extension recommends at a minimum testing for: total coliform, E. Coli, sulfate, nitrate, fluoride, copper, lead, arsenic, hardness, total dissolved solids, pH, manganese, iron, sodium.
The Virginia Extension Office runs several subsidized water clinics each year. This year, 2012, we will be having a clinic in Prince William County in the early winter. Albemarle County will be having a clinic in April 2012, Loudoun and Frederick counties will have water clinics in May 2012, Page, Shenandoah and Warren counties will have water clinics in June 2012. Water analysis for the clinics is being subsidized by the Extension program and will cost only $55 trained extension agents and volunteers will be available to interpret your results.