[Shop-talk] Tunneling drain pipe down a hill?

[Brian Kemp]

I need to make some sort of tool in the shop to run a 4" drain pipe down 
the slope in my backyard and am after the wisdom of the list to make it 
less difficult.  The upper end is a brick patio by the house (easy to 
take up) and the lower destination is a terrace about 40 feet away.  
Half the slope is too steep to stand on, so I can't really dig a trench 
to bury the pipe.  Even if I could, all the dirt would fall down the 
hill and I'd have to haul it up again, probably a couple times.  I also 
have good ground cover I'd rather not loose.

The pipe will likely be Home Depot SKU # 189781 4 inch Polyethylene 
drain pipe, cemented together.  I'll check other stores to see if I can 
find the style they used to carry with the bell ends - I think that is 
the term for the flared pipe that doesn't require a fitting, so is 
likely to be a stronger joint.

My thought is to take a piece of 2 inch wide 1/8 inch thick flat steel, 
cut some large teeth in it, and bend it into a 4 inch circle that I 
would attach around a segment of 4 inch pipe as a cutter.   I was 
thinking about rivets, but think short nuts and bolts with washers 
inside the pipe will be better.  I could start at the top and drill down 
at an angle by twisting the pipe back and forth, adding segments of pipe 
as I went.  If all went well, I'd end up at the bottom about a foot 
below the surface.  I'd dig out that segment, cut off the cutter,  
attach a 45 deg fitting, then run short horizontal segment of the pipe 
out to daylight at the terrace level.

My concern is that about 10 feet down the hill, I will be unable to saw 
the pipe back and forth, so I'll need some sort of big pipe wrench or 
clamp to grip the plastic pipe to keep sawing it back and forth.  I have 
one of these
http://www.harborfreight.com/2-inch-to-4-1-4-quarter-inch-oil-filter-wrench-36778.html 

that may be enough to grip the pipe.  If not, my backup thought is a 2x6 
ripped down the middle, hinged at one end, with a partial circle cut out 
of the middle that should hopefully give me enough grip (think oversized 
nutcracker).

If I could, I would just drill all the way to the bottom of the hill 
then flush the dirt out of the pipe when finished.  Periodically I might 
stick a hose down the pipe and flush the dirt up out the top of the 
pipe.   My concern with water is that it will find a way to the surface 
at the bottom of the pipe and cause the pipe to drift to the surface.

I have some old 3/4 inch PVC sprinkler pipe that I think I'll do a trial 
run with first.  When I've gone the distance, I'll pressurize the pipe 
with water to find the bottom end.  If it comes out where I want, I'll 
actually leave it in place to use it as a guide down the center of the 4 
inch pipe.

Anything I use has to be carried down 33 steps from the street/garage, 
so big or heavy equipment is out of the question.

I want to get gutters on the house before the California rainy season 
this year and need to get the water away from the house.

Thanks in advance for any better/improved ideas.

Brian in Los Angeles