Under Bathroom Sink Plumbing in Las Vegas

Where it is in a valley home

Inside the vanity: two angle stops at the wall, braided risers to the tap, the P-trap, and the pop-up drain rod running down behind the basin.

What usually goes wrong

• Braided risers corrode at the crimp, particularly on hot, and often weep long before they burst.
• The pop-up drain body seeps at the basin rather than the trap, which reads as a trap leak from below.
• A slow leak swells the cabinet base and softens it before anyone sees water, which is why the floor deforms first.

What to check first

1. 1

   Run the basin and then fill and release it, since an overflow or pop-up leak only shows on a full basin.

2. 2

   Press the cabinet floor. Soft or swollen board means this has been going a while.

3. 3

   Check both risers by feel, not sight, since the weep is often at the top nut.