Drinking water purity has become an important issue in the last few years. One Contaminant being talked about is TDS or Total Dissolved Solids in Drinking Water. What is the normal TDS of drinking water in ppm?
According to EPA, the limit for (TDS) Total Dissolved Solids for Drinking Water in the US is 500 ppm (Parts Per Million), but normal, acceptable Levels range between 300-500 ppm. TDS is Listed by EPA as a Secondary Contaminant, which may affect how H2O tastes, & in some cases, cause disease.
TDS in Drinking Water is more of a quality indicator of what may be dissolved in the water and can only be resolved by testing. The limits differ in other countries. TDS is the total amount of mobile charged ions, including minerals, salts, or metals dissolved in a given volume of water, expressed in units of mg per unit volume of water (mg/L), also referred to as parts per million (ppm).
Primary vs Secondary Drinking Water Standards
The EPA has established the National Primary Drinking Water Regulations (NPDWRs) that set mandatory water quality standards for drinking water contaminants. The regulations are enforceable standards called maximum contaminant levels (MCLs) which are established to protect the public against the consumption of drinking water contaminants that can pose a health risk to the public. An MCL is the maximum allowable amount of a contaminant in drinking water that is delivered to the consumer.
The EPA also established a set of regulations that is called the National Secondary Drinking Water Regulations (NSDWRs) which are considered non-mandatory for 15 water contaminants. They are established as guidelines to assist public water systems in managing their drinking water for aesthetic considerations, such as taste, color, and odor. These contaminants pose some problems but no health risk to the public consumer.
The 3 reasons that these contaminants are measured is
- Aesthetic effects — They can cause undesirable tastes or odors;
- Cosmetic effects — They have some effects which do not damage the body but are still undesirable
- Technical effects — damage to water equipment or reduced effectiveness of treatment for other contaminants
With these groups of contaminants, TDS are included along with some others that you may find in Drinking Water, like Iron and Manganese, Odor, and Color. These are found in Public and Private Wells with Hardness problems. EPA lists these as Nuisance Contaminants that can be corrected with further treatment.
They can also affect Industrial water used in specialty products for boilers or pharmaceutical products. In other words, they may need more treatment after coming from the Tap and a Municipal source. Information on Contaminants and treatments is made very available to consumers. Normally sent to customers 2 or 3 times a year or if requested, given directly to the consumers.
A Drinking Water Hotline at 1-800-426-4791. is set up Nationally to ask for the following:
- For a list of the primary and secondary contaminants for your water supplier.
- About monitoring requirements for these contaminants that your water supplier uses.
- Also, ask for a list of the health advisories available for these contaminants.
What are Total Dissolved Solids
The Best Levels or Maximum Levels of TDS are different throughout the world and for whatever application you are using it. Drinking Water is basically the same or at least very close to the same no matter the Country because of the standards established by EPA and the (WHO) World Health Organization.
Pure Water, like distilled water, is composed of 2 hydrogen atoms and 1 oxygen atom. If the sample of water is not ‘pure’, the sample’s composition can be different.
Saltwater obviously contains salt, but it can contain many other trace elements. Freshwater from different sources will contain different elements and minerals that wash into the groundwater from the Water Cycle.
Municipal Drinking Water will contain Fluoride and other chemicals added to purify water at the treatment plant. TDS is the combined content of all inorganic and organic substances contained in a liquid that is present in a molecular, ionized, or micro-granular suspended form.
TSS or Total Suspended Solids are different because they are able to be filtered, especially with the new Ultrafiltration Membranes, out of the water faster and more efficiently than solids that are dissolved.
The thinking is that the fewer TDS reading, the purer the water. The little TDS meters that are handed out with Water filters these days can be used as a comparison for municipally treated water or testing RO filters-Distillers or Ionizers that are being used as Home Water Treatment units.
They can test the efficiency of the treatment filters but shouldn’t be used to test for contaminants in the water quality of an unknown source. TDS digital probes don’t distinguish contaminants in drinking water. They are great for comparison testing and efficiency testing of Filters or mineral and sodium content of treated bottled water.
The digital meters that look like pens have been around in the Water Industry for 40 years and are fairly reliable. If you are looking to buy one, get a dual-purpose instrument for a few bucks more that can be used for other purposes. A few very good ones, and for your drinking water, you need a dependable one like;
Apera Instruments, LLC-AI3719 P
Apera Instruments Premium-Series PH60S Food pH Pocket Tester Kit, Swiss Spear pH Electrode, ±0.01 pH Accuracy, -2.00-16.00 pH Range (AI313) or
- Professionally measuring pH, conductivity, TDS, salinity, resistivity, and temp. has never been easier; also tests ORP (The ORP60-DA probe is needed)
- Cloud-based data management system – allows you to record, manage, and share your test data at your fingertips and never have to worry about data loss.
- Comprehensive Information Display – 4 types of measurement display modes to serve you in different situations.
- Upgraded pH sensor – More durable and easier to use
- Hybrid design – This product can be used as a classic tester even without connecting to a smartphone.
How to Measure TDS in Water
Using a TDS meter is the easiest way to see visually if an RO Water Filter-Distillation or Ionization Water Filtration unit is performing and working properly or need new filters or maintenance.
The truest form of testing for Total Dissolved solids in water that is done in a Professional Lab is to evaporate the water and separate them. Then weigh the remaining solids with an analytical balance. What’s leftover is any salt, metal, or mineral of unknown content for a known volume of water.
The solids are measured as mg/l or parts per/million ppm. That means if the weight left over after evaporation is 250 ppm or mg/l, then that means out of 1 million parts of water (H2O) there are 250 parts of an unknown substance.
That doesn’t mean that that substance is bad for or good for you. It only means that there is something else in the H2O other than water. For Drinking Water, if there is too much TDS in the water, you will be able to taste the difference. That’s because normally those excessive elements are usually minerals dissolved in the water that affect the taste.
If it is too little, then you will get the same reaction, and the taste will be affected. Distilled Water will have a flat taste with no mineral content to give it some taste. Drinking Distilled water isn’t good for you over any long period of time, according to researchers, but there have never been long studies on the subject that are documented.
Low TDS (total dissolved solids in water) means low mineral content in water. Some researchers believe that the minimum content of TDS should be around 150 ppm, and the maximum TDS allowable is 500 ppm. Our body requires certain valuable minerals like calcium, magnesium, potassium, etc., for good healthy functioning.
It is designed so that our body acquires these minerals from the natural universal solvent through drinking water. Mineral content can be attained from food or added to the treatment process.
Reverse Osmosis and other Home Water treatments strip minerals out of the water in the process and then replace them at the end.
Purified Water is much more important in the Industrial world, where pure water is essential for parts of the Pharmaceutical or high-tech industry. Even in Aquariums and Hydroponic systems, there should be some mineral content that is needed but then also needs to be controlled for well-natural balance systems.
In Aquaponics and Hydroponics farming, minerals and nutrients are vital for chemical and biological processes that are used by fish and crops that need to utilize for success. Other Industrial applications besides sustainable farming need purer water that is used for specific purposes. TDS is a great tool to use for monitoring these types of systems for greater control and operation.
Is Low TDS Water Harmful
Minerals found in water can be elements that are derived from the area where the water comes from. All water sources contain traces of compounds like salts and minerals that come from contact with the rocks and earth where the water is taken from. This is not always a bad thing.
These compounds In coastal areas that are dissolved can be salt contact that comes from saltwater intrusion into groundwater and Wells. The main types of Compounds that are measured in TDS of Drinking Water are:
- Calcium and Magnesium are associated with having Hard Water. Excessive levels are associated with scaling and bad taste
- Iron that, if excessive, causes bad taste and staining with use.
- Sodium Chloride can come from water softeners and saltwater intrusion or roadway salt washing into private drinking Wells.
- Sulfates are compounds found in Well water.
Because TDS is not a measure of any one specific contamination, it’s not regulated as a health issue by any governmental agency. It’s mainly an indicator and a reason for bad taste and appearance.
Water that has no measurement for Dissolved Solids may still be contaminated, and drinking water with trace amounts of TDS could be healthy and just contain these compounds that are naturally found in water that will create hardness.
Another adverse effect is if all minerals are removed from the water, then water can become more acidic and corrosive. As rain washes over some areas of the country, it dissolves minerals naturally that end up in drinking water. Too much may not be healthy, and too little might be bad for the taste and corrosiveness of pipes and tanks that have long contact with the water.
For some parts of the world, any kind of TDS reading under 200 mg/L (or ppm) is good, and 100 mg/L is considered excellent. As the TDS level goes below this level (as the minerals are removed), the Drinking water has a lower pH and becomes more acidic or corrosive and has a negative effect besides a flat taste.
Water containing TDS concentrations below 1000 mg/litre is usually acceptable to consumers, although acceptability may vary according to circumstances. However, the presence of high levels of TDS in water may be objectionable to consumers owing to the resulting taste and to excessive scaling in water pipes, heaters, boilers, and household appliances (see also the section on Hardness). Water with extremely low concentrations of TDS may also be unacceptable to consumers because of its flat, insipid taste; it is also often corrosive to water-supply systems from the World Health Organization from revised reports 2016
The best way to look at TDS is that pure water doesn’t have any dissolved substance in it. So as an indicator, a TDS test or testing probe can alarm you that there is something dissolved in the unknown water. A general water quality indicator.
It doesn’t mean that the unknown substance is dangerous; it just means that it’s dissolved in the water, and testing of the water is needed for further investigation before you consume it.
The opposite side of that thinking is that TDS might not register anything, and there still could be a toxic contaminant dissolved in the water that can be dangerous in the solution. That is the reason that a TDS test is not a reliable way of testing Drinking Water to determine how safe it is to use.
JimGalloway Author/Editor
India Water Portal- NSF -TDS in Drinking Water
EPA-Drinking Water Regulations
