You should request potable water quality for a hydro test. With potable water, you will be allowed to discharge the water without environmental permitting problems.

The secondary standard for potable water is a pH of 6.5 to 8.5 units.

Some metals many have lower limits for certain water quality parameters. Potable water quality for hydrotest of Stainless Steel Tanks shall be "maximum 50 mg/L of Chloride" in Appendix S of API 650 (Atmospheric Tank Standard).

Fluoride is not usually present in water. However, potable water typically has approximately 1 mg/L added fluoride.

Has been discussed many times on this forum:

https://www.eng-tips.com/viewthread.cfm?qid=416885

https://www.eng-tips.com/viewthread.cfm?qid=208815

https://www.eng-tips.com/viewthread.cfm?qid=352353

https://www.eng-tips.com/viewthread.cfm?qid=401685

https://www.eng-tips.com/viewthread.cfm?qid=252504

https://www.eng-tips.com/viewthread.cfm?qid=415362

https://www.eng-tips.com/viewthread.cfm?qid=208815

Thanks for the references bimr, I didn't want to go looking for them all.
I have seen lower Cl values in some end user specs. but 25ppm is the lowest that I have encountered.
50ppm Cl, and/or 100microS conductivity, and 6.5-8.5 for pH is fairly common.
Drinking water in the US is limited to 250mg/l and a TDS or 500mg/l.

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P.E. Metallurgy, consulting work welcomed

ASME PCC (#3?) also holds the same limit of 50 ppm Cl.

Huub
- You never get what you expect, you only get what you inspect.

50ppm clorides

For aust SS grades, think you need to dope the water with hydrazine also to mop up the dissolved O2 also as an added measure so chlorides dont get to corrode the metal.

George, if the system was going to sit closed I would agree.
But most of these cases the system is open to air prior to test, and then open to air after test.
Oxygen saturation is nearly assured.
I am more concerned with biological activity. I would like to see something other than bleach used, such as hydrogen peroxide.
You can buy H2O2 + peracetic acid mixtures that are very effective at 1% concentration. Straight H2O2 requires something higher than 3%.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

Agreed, biocide is a must for hydrotest media, regardless of material of construction. There are biocides that dont rely on O2 - oxidation to kill bacteria for SS grades, from memory.