I have a Paloma Tankless hotwater heater. I installed it in May of 2009. I really like this unit even though it is only 85% efficient. I have been flushing the unit with a pony pump and distilled virgin vinegar per the manufacturers instructions every 18 months. Today while I was flushing after an hour or so, the water turned green. The water in the bucket that I was recirculating was clean except it was green. Is that normal?

Acidic water flushing causes erosion in copper piping (and copper heat exchangers) which results in the water having a blue or green color. If you are properly following your manufacture's instructions for flushing, you should be OK.

Yes I called the MFG and they specifically said only to use virgin white vinegar. The inline filter was clean as a whistle and the vinegar solution seemed to be rather clean.

Thank you for the reply....