Café Leaked After Install: Drain Line Pitched Wrong

Water at a newly installed unit within days of first use. The drain run is neat and the pipework looks correct. Nothing has ever drained away properly from it.

A drain that has never worked is a commissioning question, not a fault. The fastest way to settle it is to send water down the line. A level held against the pipe measures one short section at a time and misses a dip between two of them. Water finds every low point at once, in the order the water itself meets them, which is exactly the information nobody else can supply.

Condensate moves under gravity and nothing else. A section pitched against the fall holds whatever reaches it, and once that section is full the water backs up to the unit and comes out where it can. The rest of the run may be perfect, which is why a visual check and even a spot measurement both pass. Only water travelling the whole length exposes the one section that is wrong.

The section is re-pitched to fall the whole way and the line proven again with water before anything is closed up. That order matters: prove first, make good second. A drain closed into trunking or above a ceiling before it is tested is a drain nobody will look at again until it leaks.