Someone please tell me what is this build up ? Why is it build up outside of pipe ?
There is no leaking and no hole..

The greenish i suppose is copper (that means this trap has got some copper in it)? and the white stuff ?

toilet sink trap greenish white stuff build up

enter image description here

  • i have got a bag of opened ecover laundry powder under the compartment of the sink (opening were clamped), also a few other chemical like 25% cooking acid .. all in proper bottle.. nothing spilled nothing leak ..
    – andrew_ysk
    Aug 14, 2021 at 12:50
  • Looks like something has caused a chemical reaction on the pipe. Cover everything tight, fan the space, clean the pipe, leave a gap and wait for a few days to see the result.
    – r13
    Aug 14, 2021 at 13:55

1 Answer 1


If there's no leak, (not even a tiny one) it would appear to be caused by condensation (water from the air condensing on the outside of a pipe with cold water in it) leading to corrosion.

Note that the horizontal pipe is only showing corrosion on the lower part of the pipe where the water would be inside it.

Acid fumes can aggravate that type of corrosion.

Improving ventilation, insulating the outside of the pipe, and perhaps finding a different cabinet to store the acid in would be possible solutions.

Replacing the pipe with plastic rather than metal would be another solution, if local plumbing regulations permit that.

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