blue grey water coming from tub

I have a mystery that I hope someone can offer some suggestions about. The bath tub in the apartment over my garage has bluish grey water coming from the spout. The tub also has a shower with an old hand held shower head. My tenant turns on the tub water to get it warm before showering and sometimes it comes out a bluish dark grey for 10 seconds or so. I thought maybe it was something disintegrating in the old shower head but as he turns on the tub first that doesn't seem likely.

I've read about blue water syndrome from corroding copper pipe but the color doesn't seem to match the description. I really hope it isn't that! No other fixture has the problem.

Any ideas anyone? I'm attaching a picture of the water...

I would check the tub spout nipple, it could be galvanized and is coroding.

Jerome2877 said:

I would check the tub spout nipple, it could be galvanized and is coroding.

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Thank you for the suggestion! It doesn't happen every time but maybe if it sits for a while the color builds up?

A friend suggested I drain the water heater tank and flush it but it seems that I would be seeing the blue water coming from other places if that were the problem. Do you agree? The tub is directly over the water heater so it's the shortest run in the house.

coopdedoo said:

Thank you for the suggestion! It doesn't happen every time the tub is used--does that seem strange if it's the spout nipple?

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It would depend on the length of time between uses. The longer the time between uses the more discoloration.

John