How to Increase TDS After RO Purification: Methods, TDS Controllers and Mineralizers

The most common methods are using a TDS controller, mineralizer, or controlled blending system. However, increasing TDS should not be treated as a goal by itself. A higher TDS reading does not automatically mean better or healthier water.

The important question is what substances are being added back to the water and whether the resulting water is appropriate for drinking.

Why Does RO Water Have Low TDS?

An RO membrane is designed to reject a large proportion of many dissolved substances in the incoming water.

As water passes through the membrane, many dissolved salts and other substances are retained and separated from the purified-water stream.

Consequently, RO output usually has substantially lower TDS than the source water.

For example:

The actual values vary depending on the source water, membrane, pressure, temperature and purifier design.

Why Would You Want to Increase TDS After RO?

People may want to increase the TDS of RO water for several reasons.

• To restore some minerals after RO treatment
• To alter the taste of highly demineralized water
• To adjust the final water composition
• Because the purifier is designed with a mineralization or blending stage

However, TDS itself does not tell you whether the dissolved substances are beneficial or undesirable.

Increasing TDS simply to achieve a particular number is therefore not a good water-treatment strategy.

How Can You Increase TDS After RO Purification?

There are several possible methods, but they are not equivalent.

1. Use a mineralizer
2. Use a TDS controller or blending system
3. Use a properly designed post-treatment cartridge

The safest approach is to use a system specifically designed and specified by the purifier manufacturer rather than manually adding substances to drinking water.

1. Use a Mineralizer

A mineralizer is designed to add or restore selected minerals to water after RO treatment.

Depending on the product, the cartridge may release minerals such as calcium or magnesium into the treated water.

This can increase the measured TDS while also changing the mineral composition and potentially the taste.

However, the amount and type of minerals added depend on the particular mineralizer and water chemistry.

Does a Mineralizer Increase TDS?

Yes, it can.

Because a mineralizer adds dissolved mineral ions to the water, the TDS reading can increase after the water passes through it.

The increase will vary according to the cartridge, flow rate, water chemistry and condition of the mineralizer.

2. Use a TDS Controller

Some RO purifiers include a TDS controller that allows the final output TDS to be adjusted.

A TDS controller is not itself a purification technology.

In some systems, it works by controlling the proportion of water that bypasses or does not pass through the RO membrane and is then blended with RO-treated water.

The exact mechanism varies between manufacturers and purifier models.

This means that adjusting a TDS controller can increase the final TDS without changing the RO membrane’s basic rejection process.

How Does a TDS Controller Increase TDS?

In a blending-type RO system, the controller can allow a controlled amount of appropriately filtered water to mix with the RO-treated stream.

Because the non-RO stream retains more dissolved minerals than RO permeate, blending can increase the final TDS.

For example:

This is only an illustration. Actual values depend on the purifier and source water.

Should You Adjust the TDS Controller Yourself?

It depends on the purifier.

Some manufacturers specify that TDS-control adjustment should be performed by an authorized technician because incorrect adjustment can affect the water-treatment configuration.

Before changing a TDS-control setting, check the purifier’s user manual or contact the manufacturer’s service provider.

Do not assume that turning a control valve simply makes the water healthier.

3. Use a Post-RO Mineral Cartridge

Some water purifiers use a post-RO mineral cartridge or similar treatment stage.

This stage can add selected minerals after the RO membrane.

Because minerals are dissolved into the water, the final TDS may increase.

This is different from simply blending untreated source water into RO water because a properly designed mineral cartridge is intended specifically for post-treatment.

Can You Add Minerals Manually to RO Water?

It is not recommended to manually add salt, mineral powder or other substances to drinking water simply to increase TDS.

Doing so makes it difficult to control:

• Which substances are being added
• The concentration of those substances
• The purity of the added material
• The resulting water chemistry
• Microbiological safety

A purpose-designed mineralizer or manufacturer-approved treatment system provides much better control.

Can You Mix RO Water With Tap Water to Increase TDS?

Technically, mixing water with higher TDS will increase the TDS of the resulting mixture.

However, you should not mix RO water with untreated tap, borewell or tanker water unless the other water has been appropriately treated and is known to be suitable for the intended use.

Blending untreated water can reintroduce contaminants that the RO membrane removed.

Some RO purifiers use controlled blending internally, but the system is designed so that the blending path is part of the purification process.

Does a TDS Controller Add Minerals?

Not necessarily.

A TDS controller primarily controls the final TDS level.

In blending-type systems, it may increase TDS by allowing some appropriately filtered water containing retained minerals to mix with RO water.

A mineralizer, in contrast, is specifically intended to introduce selected minerals.

TDS Controller vs Mineralizer

Does Increasing TDS Make RO Water Healthier?

Not automatically.

TDS measures the total concentration of dissolved substances. It does not tell you whether those substances are desirable minerals or unwanted contaminants.

For example, increasing TDS by adding an unwanted salt would increase the TDS reading without improving water quality.

Therefore, the composition of the dissolved substances matters more than simply achieving a particular TDS number.

What Is a Good TDS After RO?

There is no universal TDS value that every RO purifier should produce.

The appropriate final water composition depends on the source water, treatment system and applicable drinking-water requirements.

Instead of trying to achieve a specific TDS number solely because it is commonly quoted online, focus on:

• Overall source-water quality
• Contaminants that need to be removed
• RO membrane performance
• Purifier specifications
• Proper maintenance
• Appropriate mineralization or blending, if provided by the system

Is 20 TDS RO Water Safe?

A TDS reading of 20 ppm indicates very low dissolved-solids concentration, but TDS alone cannot determine whether water is safe.

The reading does not tell you the exact mineral or contaminant composition of the water.

Do not assume that increasing 20 ppm to a higher number automatically makes the water safer.

Is 50 TDS RO Water Safe?

50 ppm represents a relatively low dissolved-solids concentration.

Whether the water is suitable for drinking depends on its overall chemical and microbiological quality, not simply the TDS value.

Is 100 TDS RO Water Safe?

A reading of 100 ppm does not by itself establish drinking-water safety.

The substances contributing to that TDS and the overall quality of the water are more important than the number alone.

Is 150 TDS RO Water Safe?

150 ppm is simply a measurement of dissolved-solids concentration.

It cannot be used alone to determine whether water is safe or unsafe.

Can a Mineralizer Make RO Water Better?

A properly designed mineralizer can alter the mineral composition of RO-treated water and may improve taste for some users.

However, the presence of a mineralizer does not automatically make a purifier superior to another purifier.

The overall treatment system and the source-water quality remain more important.

Can You Increase TDS Without Reducing Purification?

Yes, if the purifier uses an appropriately designed post-treatment mineralizer or controlled blending system.

However, simply mixing untreated water with RO water can undermine the treatment process if the untreated water contains contaminants.

The safest approach is to use the manufacturer’s intended treatment configuration.

What Happens If You Increase TDS Too Much?

Increasing TDS excessively can produce water with an unnecessarily high concentration of dissolved substances.

It may also alter taste and potentially reintroduce substances that were intentionally removed by RO.

For this reason, the goal should not be to maximize TDS.

The objective should be appropriate water treatment and suitable water composition.

Can TDS Increase Naturally After RO?

Yes.

TDS readings can change because of several factors, including:

• Mineralization
• Controlled blending
• Changes in source-water TDS
• RO membrane condition
• Water temperature
• Measurement conditions

A small change in the reading does not necessarily indicate a purifier problem.

Why Is My RO TDS Increasing Without Adjustment?

If the RO output TDS gradually increases, possible causes include:

• RO membrane aging
• Membrane fouling or scaling
• Changes in feed-water TDS
• Changes in water pressure
• Temperature changes
• Incorrect TDS-control settings
• Measurement error

If the increase is significant compared with the purifier’s normal performance, the system should be inspected according to the manufacturer’s maintenance procedure.

How to Check TDS Before and After Mineralization

If your purifier has a mineralization stage, you can compare measurements at appropriate sampling points if the manufacturer provides access to them.

For example:

1. Measure the incoming water.
2. Measure RO membrane output if the system provides a suitable sampling point.
3. Measure the final drinking-water output.

This can help you understand how the purification and post-treatment stages affect the final TDS.

Use the same TDS meter, clean sampling containers and consistent measurement conditions for meaningful comparisons.

Common Mistakes When Trying to Increase TDS

Adding Table Salt

Adding salt simply to increase TDS is not an appropriate way to design drinking water.

Mixing Untreated Water With RO Water

This can reintroduce contaminants that RO was intended to remove.

Adjusting the TDS Controller Without Checking the Manual

Some systems require technician adjustment.

Chasing a Specific TDS Number

A particular TDS number does not automatically indicate better water quality.

Assuming TDS Equals Mineral Content

TDS includes many dissolved substances and does not identify their composition.

How to Increase TDS Safely After RO

The preferred approach is:

1. Use the purifier according to the manufacturer’s design.
2. If available, use the built-in mineralizer or approved post-RO mineral cartridge.
3. Use the manufacturer’s TDS-control mechanism where provided.
4. Have adjustable TDS-control components configured by an authorized technician when required.
5. Do not manually add salt or unknown substances.
6. Do not mix untreated water into drinking water simply to raise TDS.

Does Every RO Purifier Need a Mineralizer?

No.

A mineralizer is a design feature rather than a universal requirement for every RO purifier.

Whether it is useful depends on the source water, purifier design and treatment objectives.

Does Every RO Purifier Need a TDS Controller?

No.

A TDS controller is not required for every RO system.

It is used in some systems to regulate the final output TDS, often through controlled blending.

Final Verdict

The best way to increase TDS after RO purification is to use a purpose-designed mineralizer or the purifier’s manufacturer-approved TDS-control/blending system.

A mineralizer can add selected minerals, while a TDS controller can regulate final TDS in systems designed for controlled blending.

Do not manually add salt or other substances to RO water just to increase its TDS, and do not mix untreated water with RO water unless the blending system is specifically designed for that purpose.

Most importantly, higher TDS does not automatically mean healthier water. TDS is a measurement of total dissolved substances, not a measurement of nutritional value or overall water safety.

The goal of an RO purifier should be to produce water with an appropriate overall composition and contaminant profile—not simply to achieve a particular TDS number.

Frequently Asked Questions

How can I increase TDS after RO purification?

You can use a mineralizer, post-RO mineral cartridge or a manufacturer-designed TDS-control/blending system.

Does a mineralizer increase TDS?

Yes. A mineralizer can increase TDS by adding dissolved minerals to RO-treated water.

Does a TDS controller increase TDS?

It can. In systems using controlled blending, a TDS controller can increase the final TDS by regulating the amount of appropriately filtered non-RO water blended with RO water.

Can I add salt to RO water to increase TDS?

No. Adding table salt simply to increase TDS is not a recommended drinking-water treatment method.

Can I mix RO water with tap water?

Mixing with untreated water can reintroduce contaminants. Do not do this simply to increase TDS unless the water and blending system are specifically designed and verified for that purpose.

Does higher TDS mean healthier water?

No. TDS does not distinguish beneficial minerals from unwanted dissolved substances.

What is the ideal TDS after RO?

There is no single universal TDS value that every RO purifier should produce. The appropriate result depends on the source water and purification system.

Does RO remove minerals?

RO can reduce many dissolved minerals and salts along with other dissolved substances.

Does a mineralizer make RO water safe?

A mineralizer is a post-treatment component and does not replace appropriate purification. Water safety depends on the entire treatment system and source-water quality.

Why is my RO water TDS increasing?

Possible causes include membrane aging, scaling, changes in source-water TDS, water-pressure changes, temperature changes, TDS-control settings and measurement conditions.