# Buried a drainage pipe and the outlet is submerged... is it still ok?



## tireshark (Aug 17, 2014)

Dug a 200' trench to drain water from 70 feet of gutters on a house, through a 4" solid PVC pipe. Tried to be conservative with the slope, but i might have went a little overboard in spots... ended up about 5 or 6 feet deep... anyway, when i got out to the ditch i realized that the pipe was going to exit at a level that would put it underwater when a heavy rain hit. I was extremely disappointed after doing all that work, because I assumed it wouldn't function properly, and that i would have to figure something else out like maybe putting in a dry well or something. I finished installing it just before a monster rain, and left the trench uncovered as well, until i figured out what to do. 

To my surprise, even though the outlet is completely submerged by several inches, the water from the gutters is draining with apparently no issues. So am i ok with just leaving it as is then? I thought maybe it would back up or something, once the outlet got covered by water, but it seems to be working ok.

One thing to note is that i didnt cement any of the pipe junctions, but i hammered them in as far as they would go.


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## WhatRnsdownhill (Jan 13, 2016)

where does the pipe end? in a big hole in the ground or does the water run off down a hill?


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## Bondo (Dec 8, 2007)

> To my surprise, even though the outlet is completely submerged by several inches, the water from the gutters is draining with apparently no issues.


Ayuh,.... Whether the end of the pipe is underwater or not,...

Water will always seek it's own level,....


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## Daniel Holzman (Mar 10, 2009)

Water flows from higher water elevation to lower water elevation. The rate of flow depends on the difference in water elevation between the two points. So the water elevation at your outlet is lower than the water elevation at the inlet, hence the water flows. Submerged or not makes no difference to the water flow.


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## red92s (Nov 14, 2012)

To echo what others have said: You should be fine. I've got some 4" PVC drain lines that run to our curb. During heavy rains a small river forms in the "gutter" of the road, and the drain lines end up submerged (just barely). They still work fine.


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## WhatRnsdownhill (Jan 13, 2016)

it will work till it freezes, if your in a cold zone...


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## red92s (Nov 14, 2012)

WhatRnsdownhill said:


> it will work till it freezes, if your in a cold zone...


That's a good point. Never been a problem for us down here in the South.


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## tireshark (Aug 17, 2014)

Thanks guys, the pipe ends up in a large drainage ditch so it should always be able to flow out.

Great to hear this, beacuse it was a LOT of work to get that trench dug out. Had a tractor and homemade trenching attachment that helped me get it down about 2 feet, but anything deeper than that i had to do by hand. The last 60 feet was brutal, as it was down 4-6 feet at that point... still sore two days later, haha.

If i would have thought about it a little more, i hope i would have realized it would be ok... because now that i have read what you all said, it seems like a common sense thing that i should have known. I had never encountered that situation before, and i think i was maybe thinking that the ditch was going to back up into the pipe for some reason... plus i think i was a bit delusional from all the digging haha. 

Thanks again.


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## Oso954 (Jun 23, 2012)

> Submerged or not makes no difference to the water flow.


I disagree. The water rising above the mouth of the pipe changes the velocity and volume of the outflow. That reduction probably is not be critical in the OPs case.

But when you have a drainage system that, at times, is operating near the capacity of the pipe, the reduction in outflow can backup the drain system. Yes, it is still flowing, it just won't handle the entire flow requirement.


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## GeddyLee (Jan 30, 2016)

don't forget to put in a little grate cover so tiny critters don't make their way in there in drier weather


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## Johnny2509 (Mar 16, 2016)

I agree with the last response. It will restrict water flow somewhat due to blockage from existing water. However, without digging it all up, you can most likely get away with just digging it back out 6 to 10 feet and put a bend (or belly) in the pipe. As long as your end out is still lower than the drain in you will be fine and you should be able to keep if from submerging. The only thing may occur over the years is some build up of debris sediment in the belly. This is how they do draining pipes in basement to avoid too much debris going into the sump pump.


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