The Setup
Last June, we bought a 16 year old townhouse with a finished basement; the sump pump was broken at least since March, when we first saw the house, but I suspect it was broken for a much longer time based on the looks of it (it appeared to be rotted to pieces). Soon after we bought the house, my dad and I decided to replace the sump pump ourselves.
The Players
- my father, with 30+ years of homeownership experience that includes minor plumbing work
- myself, new to homeownership
- the rain, which wasn't too strong, but had started about an hour before we did
- vacancy – the home hadn't been lived in since at least December the year before; it was foreclosed and some remodeling was done to prep it for sale
Some Observations
- the water level in the pit was the same in March as it was in June; there was plenty of rain in the meantime, but water never came in the basement from what we can tell
- no water was coming into the pit while it was raining
- our unit is the second of 4 connected in a row. Our pump ejects to a pipe that merges with the neighbors' pipe. The neighbors have never had flooding
- our basement had flooded at least twice in the last 15 years
What Happened
- after we cut the pipe (below the check valve) and removed the sump pump, my father and I took it outside to marvel at its deconstruction–we surmised it could've been broken for a year or more, but we couldn't obtain any confirmation or evidence
- after we came back downstairs to continue working, we noticed the sump pit filled to nearly the brim
- about a half hour after we cut the pipe and removed the sump pump, my 3 year old noticed water coming in from the other side of the basement
- we rushed to finish installing the new sump pump
What I Want to Know
Why did the water start coming in after we cut the pipe connecting the sump pump to the outside world? I briefly talked to a plumber about it, but he didn't have an explanation. Anyone have a similar experience? I'd love to figure this one out! Thanks.
Best Answer
You removed the 1 way check valve, likely part of the pump, when you cut the line to the pump.
Your sump being low, already had a syphon ready to go, it just needed one last push to get started.
The pump of one of your neighbors started and everything in the pipes of all 4 pipes came flowing into your sump.
Your son witnessed an excellent lesson in gravity and syphons. Far more impressive than anything he will be shown even in college physics.