There is a small raised patchy area under our sink that was checked with inspection when we bought the house. Nothing was found to be leaking, and it was thought it was an old drip that was repaired, or something spilled and dried up.

That area has now turned blueish green. I do use those garbage disposal packets that foam blue. I used one tonight, and checked the area, and the patch was bone dry. There is a disposal and instant hot water dispenser hooked up.



The area is still dry, and very hard, even scratched off the top layer, and it is dry underneath.

There is nothing leaking from the pipes, disposer or hot water dispenser.

Could water or condensation from under the sink cabinet, wick upwards and cause this? But if so, wouldn't it be damp, wet, soft?

There is no indication of anything leaking downwards, as the basement was checked.

What would have caused it to turn a blueish green color?

I don't know, There may have been chemicals in the spill that are now interacting with air but if it's dry and you can't see any moisture why worry? Regards, Tom

You don't think water or moisture is wicking upwards from the plumbing underneath the cabinet? I don't know the schematics of what's under a sink cabinet,(The dishwasher is next to the sink) all I see is what's inside the cabinet, and that is not leaking at all. I wouldn't imagine any pipes or drains would be touching the cabinet in order for moisture to wick up. I would think gravity would pull it down, and then show up in the basement. I suppose I can keep an eye on it and see if anything changes. How do plumbers access these areas, pull out the sink cabinet, or access from basement? Just curious.

Thank you for replying!

"How do plumbers access these areas, pull out the sink cabinet, or access from basement?"
On a typical installation there's nothing under the sink to access. It's all in the wall. It's almost impossible for the moisture to wick up t6o where you could see it. The water would spill out onto the floor from under the cabinet first. My take on this would be a old spill t6hat may be going through chemical changes. Who knows?? Cheers, Tom

Learned something new today. Thank you again!!