What does TDS mean and how does it affect my system design when I import customized water purification RO equipment from China?

I know exactly how you feel right now. You are ready to start your bottled water business in Africa, you are looking at suppliers on Alibaba, and suddenly everyone is asking you for your “TDS value.” It feels like a test you didn’t study for, and you are worried that giving the wrong answer will cost you thousands of dollars.

TDS stands for Total Dissolved Solids, which is the total weight of all the minerals, salts, and metals dissolved in your water. It is the most critical number I need because it dictates the pump pressure, the type of pipes, and the specific membranes we must use to build your machine.

If you ignore this number or guess it, your machine might fail in a month, or you might pay for features you do not need. Let me explain exactly how this works so you can buy with confidence.

What does TDS mean and how does it affect my system design when I import customized water purification RO equipment from China?

When you send me a message on WhatsApp asking for a price, my first question is always about your raw water quality. You might think I am being difficult, but I am actually trying to save your business money.

TDS affects the design of your Reverse Osmosis (RO) system because higher TDS creates higher internal pressure, requiring stronger pumps and thicker pipes. If the TDS is high, we must upgrade the entire physical structure of the machine to handle the stress, which changes the manufacturing cost.

The best way to understand TDS is to think about a car driving up a hill. The water is the car, and the TDS is the weight of the cargo inside the car.

If the water has a low TDS (like tap water), the car is empty. It is light and easy to move. I can use a small engine (pump) and standard tires (pipes) to get it to the destination. This machine is cheaper to build and cheaper to run.

However, if your water has a high TDS (like salty borehole water or seawater), the car is fully loaded with heavy rocks. To move this heavy car up the hill, I need a much bigger engine (a high-pressure pump). I also need stronger axles and a reinforced chassis (stainless steel piping) so the car does not break under the heavy load.

In the world of water treatment, this “load” is called osmotic pressure. As the amount of dissolved solids increases, the water fights back against the cleaning process. It resists being pushed through the filter.

If you have high TDS water but you buy a standard “low TDS” machine because it was cheaper on a website, the pump will not be strong enough to push the water through. The machine will produce very little clean water, or the motor will burn out trying to work too hard.

Furthermore, the materials change. For low TDS (under 1000 ppm), we can use standard 304 Stainless Steel or even high-quality plastic (UPVC) for low-pressure piping. But if your TDS is above 5000 ppm, the salt in the water will eat through 304 steel very quickly. I must design your system using 316 Stainless Steel or Duplex Steel to prevent rust and leaks. This is why I cannot give you a proper quote without knowing this number.

How TDS Levels Change Machine Components

How does TDS affect my membrane selection when I import customized water purification RO equipment from China?

Many new buyers think that all RO membranes are the same, just like batteries. They assume they can buy any 4040 or 8040 membrane and it will fit. This is a dangerous mistake.

TDS levels determine the specific type of membrane sheet technology we must install; high TDS water requires “Água salobra” ou “água do mar” membranes that are built to reject more salt and withstand higher pressure. Using the wrong membrane will result in poor water quality or rapid equipment failure.

The membrane is the heart of your water treatment machine. Just like a human heart, it needs to be matched to the body it is serving. In the factory here in China, we have three main categories of membranes, and the choice depends entirely on your TDS report.

First, we have Low Energy Membranes. These are for very clean water, usually with TDS below 2000 ppm. They are designed to work fast with very little electricity. If you use these on high TDS water, salt will pass right through them, and your bottled water will taste salty.

Second, we have Brackish Water (BW) Membranes. This is the most common type I export to Africa. They are designed for water with TDS between 2000 ppm and 8000 ppm. They have a tighter structure. They block more minerals but require more pressure to work.

Third, we have Seawater (SW) Membranes. These are for very harsh conditions, where TDS is above 10,000 ppm or 35,000 ppm (like the ocean). These membranes are built very differently. They are extremely tight to ensure that even the smallest salt particles are caught.

Here is the critical engineering part: Rejection Rate.

Every membrane has a rejection rate, usually around 98% to 99.5%.

Let’s do the math.

If your water has a TDS of 1000 ppm and the membrane rejects 99%, the product water will have 10 ppm. This is excellent.

But, if your water has a TDS of 10,000 ppm and you use that same membrane, the product water will have 100 ppm. Still okay.

However, if you use a cheap membrane with only 95% rejection on that 10,000 ppm water, your product water is 500 ppm. That is bordering on bad taste.

Also, we must consider Flux. Flux is the speed at which water passes through the membrane. High TDS water moves slower. If I design a machine for 500 Liters Per Hour (LPH) based on low TDS, but you feed it high TDS water, that same machine might only produce 300 LPH. You will think I sold you a bad machine, but in reality, the physics of the TDS slowed it down.

When I select a membrane for your order, I am balancing the energy cost against the water quality you need. I always choose a membrane that can handle slightly higher TDS than your test result, just to be safe.

What TDS measurement method should I use to provide accurate data before I import from China?

I often have customers send me a photo of a small, $10 pen they bought online dipping into a cup of water. While this is better than nothing, it is rarely enough for a professional business plan.

You should use a professional laboratory water analysis report to provide accurate data, as a simple handheld TDS pen only gives a rough estimate and cannot identify specific dangerous ions like silica or calcium. To design a durable machine, I need to know exactly what makes up the TDS.

Let me tell you a quick story about a client of mine. He sent me a TDS reading of 2000 ppm using a small pen. I built him a standard machine. Three months later, his membranes were completely blocked, looking like white stone.

Why? Because his TDS pen only told us the total number. It did not tell us that 80% of that number was Calcium and Magnesium (Hardness). If we had known, we would have added a water softener or an antiscalant dosing system. Because we relied on a simple pen, he had to spend extra money replacing expensive parts.

A TDS meter measures electrical conductivity. It sends a small shock through the water. The more salt in the water, the faster the electricity moves. The pen then guesses the TDS based on that speed. It is a rough estimate.

For a serious business owner like you, I recommend you take a sample of your source water (borehole, river, or tap) to a local university or government testing lab. You need a Full Water Analysis.

Here is what I need to see in that report besides just the “TDS”:

1. Hardness (Calcium and Magnesium): This causes scale (white crust) that destroys membranes.

2. Silica: This is very difficult to clean. If silica is high, we need special chemicals.

4. Iron and Manganese: These turn the water red or black and will foul the membranes instantly.

6. Sulfates and Chlorides: These determine if we need special stainless steel to prevent corrosion.

When you invest in a machine from China, you are spending your hard-earned capital. Spending $50 on a lab test protects your $5,000 investment. It allows me to become your “water doctor.” I can look at the report and say, “Okay, your TDS is high, but it is mostly just salt, so it is easy to treat,” ou “Your TDS is low, but you have high iron, so we need a Manganese Sand Filter.”

Without the detailed breakdown, I am flying blind. I want to build you a machine that lasts for 5 to 10 years, not 5 months. The lab report is the blueprint I need to do that.

How will high or low TDS change my operating costs when I import a system from China?

This is the question every business owner should ask, but few do. You focus on the price of the machine (CAPEX), but the cost to run the machine (OPEX) is where your profit is made or lost.

High TDS levels significantly increase your operating costs because the system requires more electricity to generate high pressure and more chemicals to prevent scaling. Understanding this relationship helps you calculate your true profit margin per bottle of water sold.

Let’s look at the reality of running a water factory. The two biggest ongoing costs for your RO machine are electricity and consumables (chemicals and filter replacements).

1. Electricity Costs:

As we discussed earlier, high TDS requires high pressure.

• Low TDS (Tap Water): The pump might run at 1.5 kW.

• High TDS (Brackish Water): The pump might need 3.0 kW or 4.0 kW to produce the exact same amount of water.

• If electricity in your area is expensive, this doubles your production cost per liter. You need to factor this into the price you sell your water to your local customers.

• Chemical Costs:

High TDS water usually contains more “scaling” minerals. To stop these minerals from turning into rock inside your machine, we install a dosing pump. You will need to buy “Antiscalant” liquid regularly.

• For low TDS water, you might not need this at all.

• For high TDS water, this is a monthly expense you cannot skip. If you stop buying the chemical, the membranes die.

• Membrane Replacement:

In a low TDS environment, membranes can last 2 to 3 years. In a high TDS environment, even with good maintenance, they might only last 1 to 1.5 years because they are working much harder. Replacing membranes is expensive.

4. Water Recovery Rate (Waste):

This is a hidden cost.

• Low TDS: We can usually recover 50% to 70% of the water. (Input 100L, get 70L clean, 30L waste).

• High TDS: We might only recover 30% to 40%. (Input 100L, get 40L clean, 60L waste).

• If you are buying your raw water or pumping it with a generator, wasting 60% of it is expensive.
• Estimated Monthly Operating Cost Comparison (Hypothetical)

Knowing this helps you set your business plan. If you have high TDS, you must sell your bottled water at a slightly higher price to cover these costs. I want you to be profitable, so I need you to know these costs upfront.

What TDS target should I set for my final product when I import from China?

Now that we have discussed the raw water, let’s talk about the water you sell. Some clients tell me, “Lucky, I want 0 TDS! I want the purest water possible!” I usually tell them to stop and think about their customers.

You should set a TDS target between 50 ppm and 150 ppm for drinking water, as this provides the best balance between a fresh taste and health benefits. Extremely low TDS water can taste flat and acidic, which might not be popular with your customers in Africa.

O “perfect” water depends on what you are doing with it.

If you are supplying water for a battery factory, a hospital laboratory, or a pharmaceutical company, then yes, you need 0 to 5 ppm TDS. We call this deionized or ultrapure water. For this, I would design a “Double Pass RO” system for you (where the clean water goes through a second RO machine).

But if you are selling bottled drinking water ou sachet water to the public, 0 TDS is actually bad.

1. Taste: Pure water with no minerals tastes “flat” or bitter. Humans prefer water with a little bit of Magnesium and Calcium. It tastes “sweet” and refreshing.
2. Health: The World Health Organization (WHO) suggests that some minerals in water are good for our bodies.

4. pH Balance: RO technology removes minerals, which drops the pH level, making the water acidic (pH 5.5 – 6.5). If you remove all the TDS, the water becomes aggressive.

For most of my clients in Africa, the target TDS is usually equivalent to popular brands like Nestlé or Aquafina. These usually sit between 30 ppm and 120 ppm.

So, how do we achieve this if the machine removes everything?

We have two methods:

1. Blending: If your raw water is safe (no bacteria/virus), we can mix a tiny bit of filtered raw water back into the pure RO water. This raises the TDS and improves the taste.

2. Remineralization Filter: We add a final stage after the RO membrane. This filter adds healthy minerals back into the water, raising the pH and the TDS slightly to give it that perfect “água mineral” taste.
3. Recommended TDS Targets by Application

When we design your system, tell me your goal. If you want “Premium Mineral Water,” I will add the remineralization stage. If you want “Pure Water,” I will focus on high rejection. You are the boss; I am the builder.

TDS is not just a number on a screen; it is the foundation of your entire water business. It decides the cost of your machine, the monthly bills you pay, and the taste of the water you sell. Do not guess this number. Go get a proper lab test, send me the report, and let’s build a machine that fits your water perfectly.

Would you like me to review your water analysis report for you?