Don't think I ever water tested a Kerdi pan. I trust it and, never a problem...but the inspector may require it. A balloon works just fine for this...
Avanti Tile & Stone
"If you love wealth greater than Liberty, the tranquility of servitude greater than the animating contest for freedom, go home from us in peace. We seek not your council nor your arms. Crouch down and lick the hand that feeds you. May your chains set lightly upon you and may posterity forget that ye were our Countrymen."