Stainless steel pipes for demineralized water from reverse osmosis?

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Good morning everybody, 

I'm ​designing a ​Reverse Osmosis ​treatment ​facility, I ​will also ​construct it, ​capacity 40 m3/​day. The feed ​water is a mix ​of rain water ​and municipal ​drinking water (​low dissolved ​solids ​concentration). ​My client needs ​demineralized ​water for their ​production of ​stainless steel ​tubes, and he ​proposed using ​their stainless ​steel tubes for ​transporting ​the demi water ​to their ​processes. I ​know CPVC pipes ​are the proper ​ones for ​transporting ​demi water, but ​what about ​stainless steel ​pipes? Will the ​material ​corrode ​eventually? ​under which ​conditions? ​Pros and cons ​of using ​Stainless steel ​or CPVC? ​
Thanks in advance

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5 Answers

  1. Hello Sir,

    As manufacturer of RO, we use only SS316L in drinking water with low TDS (duplex required for high chloride content, which is not the case after RO). Normally, the RO is producing continuously, then no risk of stagnant water. The storage of demi water should be large enough (let's say 1 hour storage to avoid RO starts/stops too often consuming a lot of water for the flush and conductivity control). Microbio should be followed but as any part of the plant and especially at sterilization step before RO. If the design allows CIP operation, everything will be fine. 

    Best regards,

    Olivier. 

  3. I used to work in the semi-conductor business and we used DI water for cleaning wafers. We used either CPVC or PVC to achieve 21 Meg Ohm water and you couldn't get stainless clean enough.

  4. Good Afternoon Mr. Gonzalez,

    Both SS and PP (polypropylene) are used for downstream piping of RO and RODI.

    May we respectfully put the following out for your consideration;  Your question should be proposed in a meeting with your RO vendor and Customer so that both understand the application and address potential unknowns.

    Warmest regards,

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    1 Comment

    1. Alfred, agreed, the RO supplier should also answer my question, unfortunately, sometimes the supplier is a simple vendor and doesn't know in detail the technical information about their product. Appreciate your reply!

  5. There are no issues with SS. It is commonly used in the biopharm market as well as food and beverage for high purity water applications. I would however recommend using 316L Stainless for better corrosion resistance. That being said, SS offers no real benefits compared to CPVC or PVC unless the distribution piping is to be sanitized using hot water (80 C) or ozone. PVC if by far less expensive but if they are fabricating the system with their own product, the SS tubing will be at a much lower cost to them. Not to mention, they can use the system as a show piece for their products. One final thought, we typically only use CPVC instead of PVC in applications where the temperature will be elevated. Standard schedule 80 PVC will work just fine and reduce install costs. Hope this helps.

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