My main cleanout is outside but i have a floor drain in the basement. If i were to plug this drain with a test plug in an emergency like a sewer backup in the street, what would occur? Im wondering if the backup would continue upstairs where i could remove the cleanout outside for relief.... or would it recede to a lower spot in the street.

So generally whats the ramification of plugging a floor drain in an emergency?

you need to locate the nearest upstream city sewer man hole cover.

any of your fixtures below this city sewer cover (in the advent of something catastrophic) would be oozing sewage waste.

here where I live in some areas there are so many storm drains connected to the sewers that when monsoon rains hit folks with floor drains in their basement pay the price of not having a backwater valve.



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Water will seek its own level.
if you plug the floor drain the water will rise to the next higher opening.
so whether that opening is your cleanout, your neighbors floor drain or whatever, that's where it will spill out next.

So how likely is a test plug with wing nut be able to hold back a flood?



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water at a height if 1 foot exerts .433 PSI.
so a column of water 10 feet tall will exert 4.3 pounds pressure
I use that type test plug to test drainage pipes for inspection.
I use a compressor and a test gauge and put 5 PSI of air into the piping.
never had one blow out.

so what I'm saying is that if you have the drain plugged and the water backing up in the house somehow rises 10 feet up the plumbing there will be less that 4.5 PSI.
if the drain you put the plug into is clean and the plug is fully inserted and tightened well, the NY Yankees have a better chance of beating Verlander tonight than the plug blowing out.