We design and sell a complete line of DI and RO/DI hybrid water processors. So we naturally get a lot of request for information about DI material compatibility. The table below lists the most common interactions. Bear in mind that anything metallic will yield a small amount of metal back into the water until passivated, and then still smaller amounts after that. Depending on how critical you application is, be sure to perform appropriate bench-testing. Talk to your local Clean Water Crusader if you require more detailed information or design assistance.

Common Industrial Materials and their compatibility with deionized water

Material Compatibility
304 stainless steel A1-Excellent
316 stainless steel A2-Excellent
ABS plastic N/A
Acetal (Delrinr) N/A
Aluminum A2-Excellent
Brass A1-Excellent
Bronze A1-Excellent
Buna N (Nitrile) A1-Excellent
Carbon graphite A2-Excellent
Carbon Steel D-Severe Effect
Carpenter 20 A1-Excellent
Cast iron/Galvanized Iron/Ductile/Black Iron Pipe D-Severe Effect
Ceramic Al203 B-Good
Ceramic magnet N/A
ChemRaz (FFKM) D-Severe Effect
Copper D-Severe Effect
CPVC A-Excellent
EPDM A1-Excellent
Epoxy A2-Excellent
Fluorocarbon (FKM) B-Good
Hastelloy-Cr A2-Excellent
Hypalonr A2-Excellent
Hytrelr N/A
Kalrez N/A
Kel-Fr A1-Excellent
Natural rubber A-Excellent
Neoprene A-Excellent
NORYL A2-Excellent
Nylon A1-Excellent
Polycarbonate N/A
Polyetherether Ketone (PEEK) N/A
Polypropylene A2-Excellent
Polyurethane SEE BELOW
PPS (Ryton®) A-Excellent
PTFE A2-Excellent
PVC A2-Excellent
PVDF (Kynar®) A2-Excellent
Silicone N/A
Titanium A2-Excellent
Tygonr A2-Excellent
Vitonr A1-Excellent

Ratings  –  Chemical Effect


A = Excellent
B = Good

Minor Effect, slight corrosion or discoloration
C = Fair

Moderate Effect, not recommended for continuous use. Softening, loss of strength, swelling may occur

D = Severe Effect, not recommended for ANY use.

N/A = Information Not Available.

Explanation of Superscript
1. Satisfactory to 72°F (22° C)
2. Satisfactory to 120°F (48° C)

Note about Polyurethane 
Ester-based polyurethane does not perform well with water in general; discoloration, cracking and eventual leaks from water exposure are typical.
Ether-based polyurethane appears to be completely unaffected by water.
Note about Fluorocarbon (FKM)
We’ve now downgraded FKM from Excellent to Satisfactory (2017).

Some of the questions received about this page:

Q: An Auditor questioned our use of a rubber hose and Tygon tubing for transfer of DI water in our BOD testing. Was wondering if these are acceptable?

A: Certain rubbers can add to the BOD and/or COD of the water, especially at elevated temperatures.

More importantly, when BOD is critical and the process requires in-situ disinfection, rubber interacts negatively with most disinfectants and creates a home for biofilm; so I generally advise against rubber tubing where BOD is important.

Tygon generally doesn’t impact BOD (unless bacterially contaminated) and works better with a broader range of disinfectants.

When selecting tubing, also make sure that the tubing is certified for the application at the temperature.


Q: Do you have any data with RO water compatibility with stainless steels at 180 F?

A: At higher temperatures, the effects of water chemistry and dissolved gases are significantly more pronounced.

Stainless can be susceptible to corrosion when chlorides are elevated. Unfortunately, “RO Water” can be a nebulous term…Since RO is a reductive membrane separation process, it will reduce the influent contaminants by whatever the rated reduction rate is of the membrane/s at the operating TMP and flux rate; so the “purified” water quality will contain a lower percentage of contaminants than the input water.
As long as your purified water chloride level is <5ppm and your dissolved CO2 and O2 are low, one would not expect to see any corrosion or premature failure with stainless steel.

Q: Is cast iron pipe compatible with DI water?

A: Absolutely not, under no circumstances. Don’t even think about it!

Q: What material is compatible with reverse osmosis water?

A: Think of Reverse Osmosis (R/O) water like deionized water, but with more dissolved gasses. It can sometimes be more or less corrosive than DI water, depending on site-specific chemistry. Test the water and apply appropriate caution.

For more information about deionized, reverse osmosis, high purity, ultrapure, or any other water quality management project contact Aqua Mechanical 801-921-7889