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Mystery manhole cover

Looking for the source of water in a flooded basement we found a manhole cover that is 16” in diameter. Underneath is a poured concrete box 18”x18” with a dirt bottom, there are 3 clay tile pipes entering the box. I’m wondering if anyone has seen one of these before and if they know what it’s purpose was? As an extra credit question, why did it suddenly flood the basement after being dry for 10 years?

Re: Mystery manhole cover

It sounds like it's an "Invert" or collector where pipes turn or many pipes drain into one. If one is larger than the others, then that's the drain. The reason it flooded is that the drain pipe is clogged and it wasn't before. The reason it's covered is so that it can be monitored and accessed for cleaning.

You should find out what is draining into this- you might do better revising the drain system and sending that water out some other way. There's a chance the pipes go nowhere now but picked up groundwater from openings and breaks which with the now-clogged drain brought flooding. If they're unused you can fill the invert with concrete and forget it but you must know for sure or you will suddenly be flooding somewhere else! You've got some investigating to do here to know the best solution but cleaning the drain alone may be a good enough fix.


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