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What is TDS?


TDS is an abbreviation for “total dissolved solids,” certain kinds of dissolved substances that can end up in your water supply. These solids can come in a variety of forms, including organic matter, salts and chlorides.

The good news is that TDS generally isn’t a health concern in your drinking water. However, it’s not without its problems. A high TDS level can impact your water’s taste and appearance, your budget and even your hair and skin. On top of that, you may not even realize your tap water contains TDS until after these issues occur.

Fortunately, you don’t have to rely on guesswork. Here’s everything you need to know about TDS in water — from identifying to addressing it.

Understanding Total Dissolved Solids

The solids in TDS are often one or more of these substances:

  • Organic matter
  • Chlorides
  • Calcium
  • Magnesium
  • Some metals
  • Carbonates
  • Nitrates

Any of these solids can be considered TDS — but if you find one, it’s safe to assume that others aren’t far behind. One of the problems with defining TDS is that there’s no rule for which substances must be present in which amounts, so this name is more of an umbrella term than a single contaminant.

It’s also important to note that some of these solids are perfectly fine on their own. For example, your body needs calcium to maintain strong bones and magnesium for energy creation, muscle function and more. These two ingredients are also common in mineral water — which, from a certain point of view, is water that’s had TDS added on purpose. However, on the other hand, these same minerals can cause hard water, which creates significant issues for your home.

That’s why it’s difficult to call TDS a contaminant in tap or drinking water. By itself, a TDS level is just a measurement of the dissolved substances in your water — not a statement on whether those substances are “good” or “bad.”

However, that complicates things. A TDS concentration is expressed as a whole and generally isn’t broken down based on which substances are present. For example, if you were to use a home TDS tester, you’d get a result in parts per million, or ppm — but 500 ppm doesn’t tell you what those parts are, where they came from or whether you need a particular kind of water filtration.

For this reason, it’s important to understand exactly what TDS represents and how it may impact your drinking water.

TDS and Drinking Water Quality

In low or moderate amounts, TDS can enhance the taste of drinking water. After all, that’s the idea behind mineral water. But if you have higher TDS levels, that taste can become salty or bitter. This is perhaps the most noticeable problem — but it’s certainly not the only one.

Depending on the type and amount of dissolved solids, you could also notice:

  • Mineral buildup around your faucets and drains
  • Soap spots on glass and dishes
  • Dry skin and hair
  • Reduced water flow
  • Limited efficiency and lifespan for water-using appliances
  • Decreased soap lathering and cleaning product effectiveness

These are similar to the problems caused by hard water, which is the result of too much calcium and magnesium in your water supply. While they’re generally not a health concern, these minerals can cause big problems for your home and budget. That means you may need both a water filtration solution and a water softening system to address everything.

Regulatory Standards

The U.S. Environmental Protection Agency (EPA) has set a secondary limit for TDS: 500 ppm. This same number is provided by the Canadian Guidelines for Drinking Water Quality.

A “secondary limit” means a particular substance or contaminant doesn’t generally impact health in any meaningful way. Instead, the problems are considered aesthetic, which includes taste, odor and appearance issues. That said, many homeowners find they experience the negative effects of TDS at even lower levels.

How TDS Reaches Drinking Water

With so many possible meanings, even a low TDS level can lead to some big questions. One of the most important is this: “Where do these solids come from in the first place?”

Here’s a look at a few ways to break down the sources of TDS:

Organic vs. Inorganic

One possible substance in TDS is organic matter. But what’s the difference between organic and inorganic in this context? Scientifically speaking, the former has carbon and hydrogen while the latter doesn’t — but that’s not the whole story.

In this case, “organic” refers to a substance that likely came from a living organism — here, generally plant matter. This can get into your water supply in a variety of ways. For example, many municipal water systems rely on lakes and other exposed bodies of water, which means plants can:

  • Decompose on the shore and end up in the water
  • Be carried to the water by animal activity
  • Live and eventually decompose in the water itself

Some of the same possibilities exist for wells, which are often fed by underground reservoirs. These reservoirs are filled when water from nature filters through rock, which means some organic matter may remain.

Inorganic substances can still come from nature, but they include minerals and certain metals instead of living things. Water runs over, around and through rocks on its way to your tap whether you have city or well water — which means inorganic solids could frequently be present in your drinking glass.

Natural vs. Man-made

Natural vs. man-made substances aren’t classified in the same way as organic and inorganic solids. Instead, the focus is on whether the substance was introduced to the water supply from the natural environment or human activity.

This can be difficult to identify. After all, humans and nature interact in all kinds of ways. For example, road salt can be washed away by rain or snowmelt and carried to a water system’s main source by streams — but that doesn’t mean the salts themselves are now considered a natural substance.

The main focus here is what these solids could be carrying with them. Salt from rocks and minerals may introduce one problem to the water supply, but salt from road treatments could have other additives not found in nature.

However, TDS concentration measurements can’t identify sources. These tests will just tell you the overall TDS level — not whether each substance was introduced by nature itself or runoff, soil contamination and industrial discharge. That means the “natural vs. man-made” classification is generally more helpful for understanding possibilities than for making final decisions about your water quality.

Local vs. Systemic

Based on the other two classifications, it’s easy to see that TDS can be introduced to the water system at almost any stage. That means you can also break down substances based on when they might have entered your water supply.

For example, say a plant grew and died in a lake bed. This water is then taken up by pumps and pipes, sent through many kinds of treatment and then transported to your tap. By this time, the organic matter could be significantly diluted. However, if there’s a problem with the pipes closer to or inside your home, organic matter could potentially be introduced much later in the system. That means it wouldn’t have a chance to become so diluted and may lead to a noticeably higher TDS amount overall.

This is mostly relevant for wells. TDS can get into the water when it’s still rain or snowmelt, then stay there as this water filters down to the reservoir; however, TDS can also be introduced “closer to home” if dissolved substances get into the well itself.

TDS Water Testing

It’s possible to use a “TDS tester” or “TDS meter” on your own. However, the results may not be as comprehensive as you need — and you have to interpret them alone, too. That’s why DIY TDS testing generally isn’t recommended.

Instead, consider a professional water test. In 30 minutes or less, a local water expert can provide specific, detailed information about your home’s water quality. And they won’t stop at TDS levels — these tests also cover water hardness and potential contaminants like iron and chlorine. You’ll also get personalized recommendations to help you choose the right water solutions for your unique needs.

Water Solutions: Total Dissolved Solids and Beyond

While TDS may not be a health concern, it can certainly impact the taste of your water. If calcium and magnesium are present in high levels, TDS can lead to hard water issues, too.

That’s why it’s smart to consider two kinds of water solutions:

Reverse Osmosis Drinking Water Filtration

Reverse osmosis filtration, sometimes called RO, targets a broad range of contaminants and water problems. These systems don’t just address TDS; they can also reduce lead, copper, bacteria, viruses and even emerging contaminants like “forever chemicals” (also called PFAS).* That means RO water is cleaner, clearer and more refreshing.

On top of that, there’s no need to worry about removing flavorful minerals. Some RO systems have an optional mineral cartridge that gives you control over the taste of your drinking water.

You can also choose a smart RO system, which comes with a host of versatile, helpful features. For example, you can connect your filtration system to your phone to get updates and notifications — and you can even track your water usage and conservation goals.

Water Softening

For hard water issues like limescale, soap scum and mineral buildup, you’ll need a water softener. These systems trap calcium and magnesium using unique resin beads that act like magnets. Once the hard minerals are “stuck” to the beads, soft water flows out to every tap in your home. Meanwhile, the beads are rinsed with a brine solution in a process called regeneration, which is often based on a set schedule.
Don’t worry — although water softeners use sodium, which can sometimes be part of TDS, softening won’t drive those TDS levels up too far.

If you have hard water and other issues, you can also use a softener and a filtration system together; one doesn’t cancel out the other. However, it’s important to note that these two systems do separate things. The processes are entirely different. While certain softeners have built-in systems for filtering chlorine or iron, these are special cases — and even then, you may still want an RO solution for more comprehensive treatment.

Improve Your Water Quality Today

There’s a lot to know about TDS — what it really means, where it comes from, how and when it gets into your water supply, what its impacts look like and more. Despite all that, TDS is generally more of an aesthetic concern than a health issue, so there’s no need to panic. Instead, get all the facts about your home’s water quality and make informed decisions from there.

Schedule your free, in-home water test and consultation to get started.

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