Well... there is a minor setback that we found today.
I've left some water to stand inside the pond for months for testing, making sure nothing leaks. Sure, it is good enough for I did not see any sudden drop in water level, nor any wet spot surrounding the pond, as well as no wet area by the other side of walls. No sweat, no worry, the pond is all water tight.
Today I asked the workers to fill in the empty pond (just rescently cleaned and I want it filled back). There is an overflow water level check drain (4)located at the filter box to keep water level constant. This overflow drain is being plugged (to keep it from being clogged by construction debris), and out of their knowledge, complying to my request, they filled the pond full enough to over the drain level (but not to the point where water is overflowing from the pond).
Sure enough a new flaw is discovered not long after.
Now if you take a good look at the filter box. The level of watertight layer is just a bit above the planned water level. The rest above that is not water tight (crust, porous cement work). When water gets over the watertight level, disaster will happen as we witnessed not long after, the room behind was flooded by some seeping overflowing water. This would never happen if the overflow check drain is not closed. Though not a major setback and almost impossible to happen again in normal operating condition, I do not accept such flaw and decided to play the safe route.
I guess even with careful planning to details, flaws will always exist.
Adding 15-20cm of additional height to water tight layer will make sure nothing leaks to next door, even if accident happens.
Bookmarks