Concrete Clearwell

[Cannel]

I have clients with concrete underground clearwells that are worried about infliltration into the potable water. The ceilings typically have small cracks some with efflorescence evident. In my review of using membranes, liners, polurea and external liners. Each vendor tells me horror stories of the alternate methods. Need guidance on the pros and cons. I have been looking at an external membrane but is very expensive.

 

[JedClampett]

I'd verify that you have infiltration. Efflorescence doesn't always indicate active leaks. Flood the top slab and check for leaks inside. If it's leakage from groundwater they're concerned about, empty the tank and see if any liquid is entering.
Once you identify the size of the problem, the solution is more obvious. If water is pouring in from the top slab a membrane would be the way to go. If it's coming in from a few cracks, use epoxy injection. Note that if you install a membrane inside a tank and there's infiltration, the contamination might be stopped, but you'll get water in between the walls and membrane and maybe bubbles.