What Is TDS?
TDS or Total Dissolved Salts is a metric generally used to describe the hardness level of water. It basically tells us how many dissolved ions are present in our water.
Generally, these dissolved ions are of calcium and magnesium, as they are most common in hard water.
How common exactly?
Let’s just say that whenever someone is talking about their water being hard, there’s a very high chance it’s because of excess calcium and magnesium(and sometimes iron) in their water.
Apart from these commonly found ions, others that can be present in your water are the likes of nitrates, arsenic, lead, mercury, etc- which are more concerning and dangerous at much lower concentrations that calcium and magnesium.
These ions combine with other, oppositely charged ions(usually carbonates or sulfates) to form salts. All these salts together, make up the total dissolved salt levels in water. If their concentration is high enough, water is called hard.
What is ppm? Is There any difference between TDS and ppm?
Ppm stands for parts per million. To get an idea- imagine a 1000L tank, like the ones typically placed on building rooftops sometimes. Dropping one small ink drop in that tank(roughly 1 mL) will be 1 ppm or 1 part in a million.
TDS is usually measured in mg/L which stands for milligrams per Litre or 1 gram per million litres. So, saying that a particular water sample has a TDS of 1 mg/L is essentially the same as saying it has a TDS of 1 ppm.
To conclusively answer the above question- ppm and mg/L are both measures for assessing the TDS in water- and they are one and the same thing.
Are There Any Side Effects From Drinking High TDS Water?
Before I answer, a clarification- from this point onwards, ‘High TDS’ is assumed to be due to excess amounts of magnesium, calcium(and in some cases, iron) minerals in water, which, as I said are the most common contributors to hard water.
Generally if your water contains any other dissolved impurities- such as heavy metals like Chromium, Arsenic, Lead, etc- they will very rarely be in concentrations high enough to be picked up by TDS meters.
A related question to the one above also is- Are there any side effects from drinking hard water?
The answer to both of the questions is no, there are none that we know of yet. Little research has been done on the topic.
One of the few things that we know is, if the water is hard enough, drinking water can supplement some dietary requirements for minerals in our bodies. This 2013 research, one of the few that have been conducted on this topic, says the same.
So, yes- you’re probably safe drinking hard or High TDS water.
Any Side Effects From Drinking Low TDS Water?
According to a Water Quality Association(WQA) Report, anecdotal field experience tells us that there are no adverse effects from drinking low TDS water.
For instance, the US Navy provides distilled water(practically contains no TDS) for their crews to consume at sea. Even NASA provides water having TDS of about 0.05 mg/L for it’s astronauts aboard the space station.
Another common question a lot of people have is – Does low TDS water leach minerals from our bodies?
The answer to that is a resounding NO. While a shocking number of articles online cite this as a disadvantage of drinking low TDS water, it simply isn’t true. If it were, there would’ve long been a recommendation on this topic by WHO.
Scientifically speaking as well, our body’s regulatory mechanisms ensure that mineral ion concentrations are well maintained, even if we drink low TDS water regularly. To read more about this regulatory process called homeostasis, you can refer to this WQA report.
What Should Be The TDS Level of Drinking Water?
According to the WHO Recommendation on drinking water standards, here’s how they classify water quality according to TDS levels:
- TDS < 300 mg/L: Excellent
- 300 mg/L<TDS< 600 mg/L: Good
- 600 mg/L<TDS< 900 mg/L: Fair
- 900 mg/L <TDS< 1200 mg/L: Poor
- TDS> 1200 mg/L: Unacceptable
The Bureau of Indian Standards(BIS) specifies two conditions for acceptable TDS levels:
- Normal circumstances: TDS< 500 mg/L is acceptable
- Emergency circumstances where no other water source is present:TDS<2000 mg/L is acceptable
Generally though, if water has TDS greater than 500 mg/L , it is classified as hard water and you probably shouldn’t be drinking water harder than that. That’s not to say that you should drink water with a very low TDS, say 30, because you do need a minimum level of minerals to be present in the water to make it fit for consumption- otherwise it just becomes unhealthy. Having said that, no public health organization around the world has specified a minimum limit for TDS.
Now, I know all this can be a bit confusing, so here’s the general rule of thumb I follow:
Keep the TDS levels of your drinking water in the range of 100-500 mg/L. As long as you’re in this range, you’ll be fine. Personally though, I find that water with a TDS>150-175 doesn’t taste that great to me, it tastes kind of heavy. It all depends on your taste, though. Some people prefer to drink much harder water.
How to Reduce TDS in Water At Home?
#1 Reverse Osmosis(RO) filter:
RO water purifiers are the only commercially available option for lowering TDS in water and making it fit for consumption. The clear advantages of RO purifiers are that they remove all viruses, bacteria, cysts and protozoa(the entire range of water-borne contaminants basically) as well as dissolved impurities such as salts, heavy metals, chlorine and chloramine, etc.
However, they waste quite a bit of water in the process. For every Litre of pure water, they waste about 1.5 L. Here’s my recommendation:
If you’re okay with the current taste of your hard water, and it doesn’t contain harmful contaminants like heavy metals- don’t buy a RO purifier.
To make this call though, you need to know about the contaminants in your water. Residents in US can call their water supplier and simply find out. American water suppliers are also required to release an annual water quality report.
You can also get an inexpensive home test kit, such as this one on Amazon for testing for various common water contaminants. You can read more about RO water purifiers over here: RO Vs UV Vs UF: How To Choose a Water Purifier
#2 Boiling Water
I mentioned earlier in the article that Calcium and Magnesium ions make water hard by combining with carbonates and sulfates to form salts. Not all hard water minerals are the same though- some are temporary and can be removed by boiling water, while others are permanent and cannot be boiled out.
So, what exactly is the difference between temporary and permanent hardness of water?
Temporary hardness is due to formation of carbonate salts in water such as Calicum/ Magnesium Carbonates. This usually happens in areas where the groundwater has passed through limestone.
Permanent hardness refers to the formation of calcium and magnesium sulfates in water. These can only be removed through a RO purifier at home.
A lot of people falsely believe that boiling reduces total water hardness- i.e: permanent and temporary hardness taken together. This is because TDS testers only indicate the overall TDS concentration in water. They do not test the type of minerals dissolved in water, which leads to this misconception.
#3 Water Softener:
All right, I know that water softeners don’t reduce TDS. However, they do make hard water soft, so I’m adding this recommendation here because a lot of people often confuse TDS and water hardness. I know a lot of you are just looking for ways to make your water soft for home usage.
Acc to popular mechanics, there are two types of water softeners:
- Salt Based Water Softeners: The first type works via ion exchange technology – by replacing Magnesium and Chlorine ions in water with Sodium.
- Salt Free Water Softeners: There also exist salt free water softeners. Generally not as useful as salt based softeners, these these just work to prevent scaling or accumulation of hard water salts in pipes, tiles or other surfaces at home where hard water comes into contact.
Water softeners are great for preventing mineral build-up in your plumbing, on your bathroom tiles, shower heads, etc. Your skin and hair will feel better(hard water is very drying) and your clothes will look brighter after washing them. You can also drink softened water, provided you’re not specifically on a low sodium diet.
Keep in mind though- water softeners are usually whole house solutions and expensive, at that. If you are thinking of getting one, I’d recommend a salt based water softener, like this one on Amazon.
How To Measure The TDS In Water At Home?
Just measuring TDS isn’t going to tell you about your water quality. No TDS meter can tell what the salt composition actually is.
Also, if your water contains nitrates, arsenic, lead, etc, they become dangerous at a ppb(Parts Per Billion) level. Well, TDS meters are calibrated at ppm(Parts Per Million) and aren’t sensitive enough to detect these harmful dissolved salts. So, if you ask me whether TDS is a good measure for water quality? My answer would be- no, not in most cases.
Here’s what I recommend:
Get a complete water quality testing kit, such as this one on Amazon. This will help determine your water quality and find out whether there are any other dissolved hard water salts apart from the usual(Magnesium and Calcium), as well as other contaminants.
After that, if you decide to reduce TDS in your water by one of the above methods, you can choose to buy a TDS meter to monitor your filtered water levels periodically. They’re available on Amazon and are quite inexpensive.
It’s important to know what exactly is the composition of the Total Dissolved Salts(TDS) in your water before taking the next step. My advice- if you don’t mind the taste of your water, you don’t need to reduce TDS. Like I said- as long as your water doesn’t contain heavy metals or excess chlorine and chloramines, there will be no side effects from drinking water that has a high TDS or even low TDS water, for that matter.
What matters is- what tastes the best to you? Decide according to that.