Technical Opinion on SS304 Potable Water Line Leakage 1

[Suradach]

Dear Expert
We have encountered a leakage issue on a Stainless Steel 304 (SS304) pipe used in a potable water system, which has been in service for less than six months. We would like to kindly request your assistance in reviewing the case and providing your professional opinion on the possible causes.
Preliminary observations:

• Pipe specification: SS304, Schedule 10
• Service: Potable water, no chemical additives
• Leakage point: Along the straight pipe (not on the welded joint)
• No excessive pressure or visible mechanical impact

We would greatly appreciate your recommendations on the following:

1. Possible causes of leakage in such a short service period
2. Suggested short-term repair methods (e.g., clamp, welding, or others)
3. Long-term preventive measures, such as material selection or water treatment adjustments

Thank you in advance for your valuable support.

 

[MintJulep]

Sensitization.

https://www.rolledalloys.com/what-is-sensitization-and-how-to-avoid-it/

Likely made worse by using carbon steel tools, and tools contaminated with carbon steel during cutting, joint prep and welding.

 

[Suradach]

Sensitization.

https://www.rolledalloys.com/what-is-sensitization-and-how-to-avoid-it/

Likely made worse by using carbon steel tools, and tools contaminated with carbon steel during cutting, joint prep and welding.

Thank you for sharing.
In the short term, the client intends to replace the damaged pipe section as a temporary fix. For the long term, they are considering installing a filter to reduce or control chlorine levels to below 200 ppm or possibly replacing the piping with SS316L material.

 

[LittleInch]

200ppm chlorine!! And you call this potable water??

No wonder its leaking from the inside.

 

[GD2]

OP,
You got two problems here:
1. Welding of SS, if proper precautions and Welding Procedure not maintained.
2. Chlorine environment that gives rise to ClSCC. Chlorine might even come from the hydrotest if it was not checked/controlled.

Did you say it has cracked longitudinally? It can do so only by the circumferential stress. Look for any upset/excursion or hydrotest condition that exceeded the YS of the pipe material.

 

[MintJulep]

Potable water limit is 4 ppm chlorine, so not potable water.

304 SS bad choice at 200 ppm.

 

[GBTorpenhow]

OP likely means 200 ppm chloride (Cl-). EPA limit is 4 ppm on chlorine (Cl2). Very different things.

 

[bimr]

The U.S. Environmental Protection Agency (EPA) has established a secondary drinking water standard of 250 mg/L for chloride. This standard is not legally enforceable but serves as a guideline for water systems, primarily addressing aesthetic issues like taste and potential corrosion. While there isn't a primary (health-based) standard for chloride, the EPA recommends that individuals on restricted sodium diets limit their sodium intake from drinking water to 20 mg/L.

 

[pierreick]

Hi,
Attached standard in Thailand on drinking water:

Drinking Water Quality Standard in Thailand

People don't drink tap water in Thailand unless they have no other option.
Definitely SS304 is a bad choice, most of the time people are using PE pipe.
Pierre

 

[SJones]

1. Incorrect materials selection: 304 didn’t stand much of a chance
2. Cut and replace
3. Select a more appropriate grade - applies also to 2, and adopt tighter welding and hydrotest practices

 

[pierreick]

Attached a set of handbooks to support your work.
Pierre

Library - SSINA

www.ssina.com

 

[EdStainless]

I wouldn't trust generic 316L at 200ppm Cl.
You can get it to work but it takes a lot of technical tricks.
The welded pipe needs to have very lower residual delta ferrite in the welds, <0.5%.
Your welding in the field needs to all be automated orbital with a well developed process.
In sch10 I presume that these are all autogenous welds.
These welds also need to be low delta ferrite, no visible heat tint, full penetration, and very smooth.
This is the kind of work done in pharmaceutical plants for high purity water systems.