Question
Hi Marc,

Hope you can help me with a drainage question.

My home site slopes from back to front.  I am trying to install 2 NDS 12" catch
basins one at the back corner of yard and one at back corner of house.  It will be
connected by 4" drainage pipe outleting to front yard near the street.

My question has to do with pitch.  1/4 inch per foot is the usual recommended
pitch.  However, due to a number of factors.......underground utilities, length of run
from back yard to front, I'm not sure if that pitch is feasible.  

With 4" pipe, and the fact that it is only rain water and not solid waste, can I get
away with using less pitch.

With 4" pipe and maybe 1/8 inch per foot pitch, is this adequate?

Any help would be greatly appreciated.

Thanks,

Ed

Answer
Yes - If done with care.  You are talking about a 1% slope, so silt in the pipe will accumulate more quickly.  You just have to "flush" it more frequently - Insert a garden hose with a spray nozzle attached & with the water turned on once a year or so.  

You should be able to notice when it is not draining and time for a "flush".  You'd be surprised what crawls, falls, or gurgles into these things!

I would add a grate & riser (NDS #11, #14 or #40, depending on pipe size & desired color), or catch basin (NDS #900) every so often, so the length of garden hose you have to use is less than 50 feet.  Otherwise, cleaning it out would be "pushing on a rope". These openings don't have to be functional - they are merely access points to clean the line.

I have a cool little drain-cleaning attachment for my garden hose - it works on clogged kitchen sinks, too. Found it at True Value.  Looks like a root-feeding nozzle, but it is on a flexible piece of plastic that blasts water in all directions...Really messy if you pull it out while the water is running!

~M