Reverse Osmosis: Does It Corrode Pipes?

Reverse Osmosis: Does It Corrode Pipes?

If you’re a homeowner who is considering adding a reverse osmosis system to treat your tap water, you may be wondering if it will corrode your pipes. The answer is…it depends.

Reverse osmosis corrodes some pipe materials, including plumbing fixtures, depending on what materials they are made of. Pipes made of copper, steel, galvanized steel, iron, and stainless steel are corroded by RO water. The amount of degradation depends on the type of metal as well as your water’s pH and TDS concentration. Plastic pipes, such as PEX, polypropylene, and PVDF, are compatible with reverse osmosis treated water and can be used safely in your home.

In this blog post, we’ll take a look at the factors that can affect whether or not reverse osmosis will corrode your pipes, what makes RO water “aggressive, how to prevent corrosion, and a lot more.

Reverse Osmosis and Metal Corrosion

Water and corrosion

Water is the universal solvent. It dissolves the metal in your pipes and can cause corrosion, too.

Natural water and tap water typically have some amount of hardness (calcium and magnesium) and alkalinity. These minerals and dissolved solids protect metal pipes like copper and steel by forming a layer of carbonate scale. This layer is not harmful to the pipes and forms a barrier between the vulnerable metal and water.

The reason that most homes, even those with older iron galvanized plumbing, don’t experience significant corrosion is because the TDS in the municipal water is so high. These pipes are protected by the deposit of dissolved solids that naturally occurs.

Reverse osmosis removes “protective” TDS

Reverse osmosis treated water is often referred to as being “pure”. This is because RO removes a wide range of impurities and contaminants. It also removes most of the protective TDS present in tap water.

The more “pure” your water is, the more corrosive it is. Water with low levels of TDS is considered to be corrosive. The lower the TDS concentration, the greater the likelihood that RO water will corrode pipes.

RO treated water is corrosive because the dissolved solids that would normally form a protective layer inside your pipes have been filtered out. Because the hardness and alkalinity have been removed, the water is unable to form deposits or scale, and your plumbing system is unprotected.

Reverse osmosis and low pH

Another issue with reverse osmosis water is its pH. RO filters allow carbon dioxide to pass through which produces carbonic acid. This is a mild acid that lowers the pH of treated water. Low pH is corrosive to the metals that are typically used in plumbing fixtures and pipes.

Does Reverse Osmosis Water Corrode Copper Pipescorroded copper pipes from reverse osmosis system

Reverse osmosis water treatment can be a great way to improve the quality of your tap water. However, it’s important to be aware that this type of water treatment can also lead to corrosion of metal pipes. In particular, copper pipes can be susceptible to leaching and pitting when exposed to reverse osmosis water.

This is because reverse osmosis water has a low pH and little to no alkalinity or hardness, which can make it quite aggressive on metal distribution piping. If you are considering adding a reverse osmosis system to your home, it’s important to be aware of this potential issue and take steps to protect your pipes.

If you already have a reverse osmosis system installed, be sure to check your copper pipes regularly for signs of leaching or pitting. If you notice any issues, take steps to correct them immediately. By taking these precautions, you can help ensure that your reverse osmosis system works safely and effectively for years to come.

Does Reverse Osmosis Water Corrode Galvanized Pipesgalvanized steel pipe corrosion from reverse osmosis

Galvanized piping will corrode with time, even under ideal circumstances. The average service life is 25 to 40 years. If you have a reverse osmosis system, your galvanized pipes can fail more quickly. While the pipes appear fine on the outside, they can be rusting on the inside.

If you’re considering adding a reverse osmosis system to treat your tap water, you may be concerned about the potential for corrosion and damage to your piping system.

Reverse osmosis filters remove hardness, alkalinity and other dissolved solids from the water. These minerals provide protection for metal piping by forming a thin layer of carbonate scale. Without this protective coating, the aggressive RO water will dissolve and corrode the galvanized steel pipe.

New pipe will resist this corrosive action much better than older pipes. Unfortunately, most galvanized piping is in older buildings and is likely already beginning to corrode. The reverse osmosis treated water will only accelerate this problem.

Does Reverse Osmosis Water Corrode Stainless Steel Pipes

If you’re considering adding a reverse osmosis system to your home, you may be worried about the potential for corrosion caused by the treated water.

Normally, stainless steel is very resistant to corrosion and will not corrode for many years. This is why it is used in many industrial applications. However, the aggressive nature of RO treated water can reduce the normal service life of stainless steel piping.

For this reason, I would recommend using a different type of piping if you’re installing a new reverse osmosis system. If your home already has stainless steel pipes or fittings, they will be fine.

Does Reverse Osmosis Water Corrode Lead Pipeslead pipe corrosion

Lead pipes and lead-containing solder were used in the plumbing system of many homes. This problem is mostly encountered in homes built before 1986. Most municipalities treat the tap water to inhibit the leaching of lead from the pipes and solder. However, RO removes the protective chemicals added allowing the water to dissolve the lead.

This issue can be confusing because reverse osmosis is very effective at removing lead from contaminated water. Unfortunately, once the water has passed through the RO filter, it is very aggressive and can dissolve and leach the lead from the pipes and solder.

If you suspect that your house has either lead piping or lead-containing solder, you should not install a reverse osmosis filter. If you want to treat your water using RO, then you should remove the lead piping and replace it with PEX or another compatible material.

Does Reverse Osmosis Water Damage PVC Pipes

If you’re considering adding a reverse osmosis system to filter your tap water, you may be wondering if it will corrode your pipes.

While PVC pipe is generally compatible with a variety of chemicals – acids, bases, and mild solvents, it is not recommended for use with reverse osmosis systems. The aggressive nature of the RO treated water will extract additives from the PVC, weakening the piping structure and contaminating the high-purity water.

Does Reverse Osmosis Water Damage PEX Pipes

Many have discovered that PEX pipe/tubing works well with reverse osmosis systems. PEX is resistant to mineral and other contaminants in the water, so it doesn’t rust or degrade.

If you are considering adding a reverse osmosis system to your home in order to treat your tap water, you may be concerned about the potential for corrosion caused by the RO filter. However, PEX piping is resistant to corrosion and can handle the constant exposure to the aggressive reverse osmosis treated water.

PEX piping has been installed in many homes that have RO filters without any problems. The pipe holds up well to the corrosive water, and its service life is not compromised at all.

Which Pipe Material is Best for RO Water

Reverse osmosis water is much more corrosive than untreated tap water. It is especially damaging to metal pipes made from copper, iron, steel, and galvanized steel. It is only partially corrosive to stainless steel.

The best pipe materials to use with reverse osmosis systems are:

  1. PEX
  2. polyproplylene
  3. PVDF

What Can You Do to Prevent Corrosion of Your Pipes

Reverse osmosis water is known to corrode metal pipes. As a result, you may experience problems with your plumbing if you have a RO system installed in your home.

There are a few things that you can do to prevent corrosion of your pipes. :

use pipe materials that are resistant to RO water (PEX, polypropylene, PVDF)

install an inline filter to remove contaminants from

Increase the alkalinity of your waterRO remineralizer

One way to reduce the aggressiveness of the reverse osmosis treated water is to increase the alkalinity. You can install a remineralization filter after the RO unit or add an alkalinity filter cartridge to your system.

Either of these would add alkalinity to your treated water which would reduce its corrosiveness. Many people find that adding alkalinity also improves the flavor of the treated water.

Replace your metal pipes with PEX

To protect your plumbing from the aggressive and corrosive RO water, you can replace your metal pipes with plastic pipes. The best material to use is PEX.

PEX is a common piping material used in plumbing and is known for its durability. It is resistant to a variety of chemicals, including reverse osmosis water. PEX will not corrode or degrade over time, and it has a long service life.

You can also use polypropylene or PVDF piping

Install an under-sink RO filter

Rather than installing a whole-house reverse osmosis filter – which would degrade and corrode the plumbing throughout your home, you could install an under-sink RO system. This would limit the piping that is exposed to the aggressive water to the tubing that connect the filter to the faucet.

If you have a dedicated reverse osmosis faucet, then all of the materials of construction would be compatible with the treated water.


Does reverse osmosis water leach copper from pipes?

Reverse osmosis treated water will dissolve copper from pipes because it is slightly acidic with very low TDS concentrations. Normally, the alkalinity and hardness present in natural and tap water will form a protective coating on the inside of copper pipes. Reverse osmosis removes these minerals, and the aggressive water will corrode and pit the copper pipes.

Does reverse osmosis water leach lead from pipes?

RO filtered water will leach lead from pipes because it has a slightly acidic pH and very low alkalinity and carbonate levels. This combination causes the reverse osmosis water to leach lead and can produce dangerous levels of lead.

Does reverse osmosis water corrode brass?

Brass isn’t as easy to corrode as copper in a reverse osmosis system, but it should still be avoided downstream of the RO filter.


Reverse osmosis water is more corrosive than untreated water and can cause problems with your plumbing. Metal pipes and fittings are vulnerable to corrosion and leaching from the aggressive RO treated water. Copper and iron pipes are the most susceptible to corrosion and should be avoided if possible.

You can prevent corrosion by using pipe materials that are resistant to RO water, adding an inline filter, or increasing the alkalinity of your water. You can also replace your metal pipes with PEX piping.

Pipe corrosion is a serious issue that every homeowner should be aware of – especially if you are considering adding a reverse osmosis system to your home.

Boch Richard

Richard Boch is a chemical engineer responsible for designing water filtration systems for industrial and residential customers. He has more than 20 years of experience with ion exchange, activated carbon, and reverse osmosis. Richard's expertise has made him a go-to source for municipalities and businesses looking to improve their water quality. When he's not working, Richard enjoys spending time with his wife and two young children.

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