Elevated Mg in a recirc loop post pump

[adirondackweldor]

As part of our PW system, we have a break tank and recirc loop that we installed to isolate our pre-treatment zone from the the municipal mains. The wildly fluctuating pressure of the city water was playing havoc with our softeners mostly. The oddity we have been experiencing is elevated magnesium levels at a sample port just downstream of the booster pump for the recirc loop. This is a Grundfos SS unit, that at least from my research has nothing in it that might slough magnesium. Of course there may be some Mg getting by the softeners, and getting into the recirc system during times that water is just cycling through, but if that was the case, the elevated numbers would be throughout the loop I would think. Anyone ever experience a phenomenon like this?

 

[EdStainless]

Do you have any equipment that may have been manufactured with anodes on to suppress galvanic corrosion?

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Plymouth Tube

 

[adirondackweldor]

Thanks for your reply. No nothing of the kind. In looking into the colorimetric method that we use to measure these values, I found that this test can be influenced by a number of different metals, including Cr. The pump having a number of 314L parts, might be giving up some chromium due to chlorine attack from the chlorine in the muni water. Our chlorine levels are low, but I suppose it's possible.

 

[MedicineEng]

If you suspect that your pumps are releasing Cr, open it and make an internal checking. Also, what chlorine levels are we speaking about? I am not sure if the chlorine levels are sufficient to attack your pumps.
Or if you have a spare pump, replace it and check again for Mg problem.