Water Filtration for All Building Types
Healthy Building Science (HBS) recommends water filtration for all building types, whether the water is from a treated municipal source or an onsite well or reservoir. Filtration systems for potable water and bathing should be treated with a minimum of a whole-building system and/or under-the-sink filter with sufficient filtration media to address known contaminants. Water quality testing is essential in specifying and sizing an appropriate water filtration system. Systems should be installed and maintained according to manufacturer requirements.
Water Filtration Overview
Water delivers nutrients and oxygen to our cells, removes toxins, and supports the body’s natural healing processes (source). The average adult is 60% water, making its quality inextricably tied to our health. Unfortunately, water sources contain many different types of contaminants that disrupt our bodies and the environment. Water treatment facilities are not equipped to handle all types of pollutants, and some “treatments” add harmful byproducts to water. As a result, HBS recommends that building occupants install water filtration systems. This statement will not address water-pitcher filters, as we do not believe that these filters adequately remove contaminants. Instead we address whole house and under the sink filters.
There is not one filtration method that can tackle all contaminants. Consequently, the first step in deciding upon a filtration system is determining what contaminants are in the source water. HBS recommends getting your water tested for a broad spectrum of water contaminants, both inorganic and organic. With that said, water testing results do change over time. According to the WELL Building Standard, water is affected by changing industrial practices, variations in temperature, pH, and weather. Nevertheless, test results do give you a good place to start. Oftentimes an assemblage of filters is needed to address all pollutants. Primary contaminants include residual pesticides, pharmaceuticals, turbidity, VOCs, heavy metals, chlorine, chloramine, fluoride, trihalomethanes (THM) and haloacetic acids (HAA). These contaminants in turn can affect taste, odor, and color.
The following filters address the majority of these pollutants: Sediment Filter, Carbon Filter, Reverse Osmosis, & UV Sanitization.
Water Filtration Options – Strengths and Weaknesses
Sediment filtration is designed to remove suspended solids, it does not address chemicals, heavy metals, or impurities that affect smell or taste. 
HBS suggests coupling a sediment filter with a carbon filter or a reverse osmosis filter. If your water source is not municipally treated it is good to use a sediment filter, otherwise you run the risk that your carbon or RO filters will become prematurely clogged with fine sediment. If your water source is municipally treated you may not need a sediment filtration system but can rely on the pre-filter that accompanies RO and carbon filters from getting clogged with particulates. Pre-filters allow RO and carbon filters to work more effectively and extend their useful life.
Carbon filtration removes VOCs, chlorine, chloramine, pesticides, and some pharmaceuticals. The removal of chloramine is more difficult than the removal of chlorine. As a result it is important to know what disinfectants your municipal water treatment centers use. You can find this out by reading your county’s water report. If your county uses chloramine then it is important to get a system specifically designed for chloramine. The carbon bed needs to be deeper and the water needs to pass through it more slowly (source).
If possible, Healthy Building Science recommends a whole building carbon filter. Filter size should correspond with anticipated water usage. Make sure that your carbon filter is comprised of 100% carbon with no metal resins or silver impregnation. A backwashing mechanism that allows for the filter to be periodically flushed will extend the useful life of a carbon filter. The benefit of backwashing is that it clears away already caught sediment and loosens up the carbon block, which can become compacted by incoming water. Loosening the carbon creates more surface area, which allows for the carbon to trap more contaminants. The downside to backwashing is that it requires a large amount of wastewater. This water is not potable and should ideally be harvested for other purposes, such as irrigation of non-edible vegetation. Though carbon filtration removes a great deal of contaminants it does not remove them all. A quality whole building system should remove contaminants 20 microns and larger. To give a point of reference, a strand of hair is 100 microns wide. Carbon filtration does not address fluoride, nor is it particularly good at removing heavy metals.
Installing a whole building carbon filter is beneficial because in addition to removing contaminants from drinking water, a whole house system also filters bath and shower water. This is particularly important because chemicals, chlorine, chloramine, and their disinfectant byproducts, trihalomethanes (THMs) and haleoacetic acids (HAAs) are transdermal and can also be inhaled through steam (source). These chemicals have been linked to health problems such as skin irritation,asthma, heart disease and cancer (for more articles please see further research below). Fortunately whole house carbon filters do a great job of filtering these contaminants.
Reverse Osmosis (RO), removes heavy metals such as lead, mercury, and arsenic, as well as fluoride, disinfectant byproducts, microbial cysts and chemicals that were not addressed by carbon filters. An RO filter can remove particles as small as .001 microns. Once water goes through an RO system it is referred to as “pure”. This is both good and bad. The good is that the RO filter removes many types of contaminants, the bad is that with these contaminants include minerals essential to our health, including calcium, magnesium, and iron. Deficiency in these minerals produce negative health effects. There is still debate within the scientific community regarding the extent to which RO water can create health risks, however the studies that do show the negative consequences of RO filtration are compelling and should be taken into consideration.
For example, the Czech Republic National Institute of Public Health’s paper Health Risks From Drinking Demineralised Water, states that “for about 50 years epidemiological studies in many countries all over the world have reported that soft water (i.e. water low in calcium and magnesium)…is associated with increased morbidity and mortality from cardiovascular disease compared to hard water and water high in magnesium.” The paper goes on to say that “recent studies also suggest that the intake of soft water, i.e. water low in calcium, may be associated with higher risk of fracture in children and neurodegenerative diseases.” (source). This paper has been cited by the World Health Organization. Additionally Mary Cardaro, a building biologist who has designed her own under the sink filter includes remineralization as part of her filtration system. She explains that demineralized water “lacks some of the actual good minerals that have been removed along with all the bad contaminants way back in the first phase. So at this state calcium, magnesium, and coral calcium are now added to the water stream to add a small amount of minerals- just enough to properly balance the pH of the water and energize the water, giving it more electrons.”
Though the verdict is still out on the risks of RO filtration, Healthy Building Science recommends erring on the side of caution. If you are going to use an RO system, we recommend that the water go through a high quality remineralization process that adds beneficial minerals back into the water. The placement of the RO system should be under the sink after it has travelled through the building’s piping.
Ultra Violet (UV) Sanitation. A final option for filtration is UV sanitation. UV water filtration is good for addressing microbiologicals that may be present in well water. A properly sized and functioning UV system kills potentially harmful bacteria and microorganisms. Flow-rate must be sufficiently slow for UV to work effectively. UV sanitation is generally only prescribed for well or surface water applications where municipal treatment for bacteria has not already occurred. UV only kills living organisms and has no impact on chemicals, metals, color, odor, or sediments.
There is no blanket answer to which filtration system to choose. Proper selection depends on the contaminants in your water. Carbon filtration is definitely recommended while a Reverse Osmosis system is only recommended if it goes through a remineralization process. With any filtration system it is very important to regularly replace filters according to the manufacturer’s specifications. Though most of us do not have access to clean and fresh spring water, we do have the technology to vastly improve our water quality. Finally, and perhaps most importantly, the more we find ways to protect our water sources, the less we will need to rely on filters.
Further research on Water Filtration
Lung hyperpermeability and asthma prevalence in school children