French Drain Flow Rates

[layfieldman]

I'm looking for typical flow rates through a french drain with perforated pipe in it. Say 1' x 1' cross section. Does anyone have data or knows where I can get such data?

Also, does anyone know of any alternates to gather flow sub surface?

 

[dicksewerrat]

You need the hydrualic capacity of the soil, the medium the drain is in and the slope of the pipe. Not to mention the height of the water table. Talk to the neigthbors that have drains and sump pumps.

 

[layfieldman]

Thanks for your response.

I am doing a comparison for drainage systems under sports fields and I want to do is a comparative analysis of different systems based on maximum drainage rates.

The flow rates I'm looking for would be for a rock filled trench wrapped in a non-woven geotextile with the dimensions from my original post. Slope would be around 1% with no water table. I need an estimate only on what the maximum flow rate that the french drain would be capable of handling.

 

[BigH]

Check out Cedergren's book - should be able to assist you in figuring out how to estimate the flow rate.

 

[layfieldman]

Thanks again but I already knew of his book and might have to run out to the library to check it out. I don't really want to pay over $100 CDN for what I'm doing though. Our company is trying to decide whether to invest in a certain system and just want to compare it to what already is available.

 

[dicksewerrat]

The max. would be the full pipe Q for your pipe size and slope.

 

[BigH]

I'd go to the library - its a small investment for your company compared to what may happen. Vancouver?

 

[cvg]

basic hydraulics will give you the capacity of the pipe. Assume gravity / full flow for the maximum capacity. I wouldn't consider the rock filled trench to convey water, just the pipe. The trench collects the water from the surrounding soild and then just transmits it into the pipe.

 

[golfer2]

cvg is right just consider the flow rate ofthe pipe this formula should help.

36.4*SQRT((H/L*D)^5)