On 10/6/2011 5:11 PM, tim birr wrote:

UPDATE

OP again...Dug out around the edge and disconnected the downspout from
above.

I can see into the hole. The one-inch steel pipe goes through the
slab and into the mouth of a three-inch clay drainpipe (the clay looks
and feels like red "brick" sort of material).

The clay is apparently clogged somewhere nearby, it does not take much
water to make the clay pipe back-up. When it backs up, it just spills
over the top of the clay pipe, which is set about two inches (more or
less) under the cement slab.

The water is then flowing away, creating a tunnel near the house.

I tried flushing with high pressure water from the top, but no luck.

Since the end of this drain is at least 100 yards away, maybe more,
and numerous other downspouts connect, I can't see any chance of
clearing this from below -- esp. since the clog appears to be fairly
close to the top. The water backs up pretty quickly.

Any other thoughts, other than running a new drain line down the hill
-- I think my snake would probably crack the pipe.

I don't think drain cleaner is indicated for clay pipes...

Just had this problem on a 2 year old house. One of the 4" corrugated
downspout lines appeared to be clogged. I tried putting a garden hose
through it with a nozzle shooting straight ahead. I got about 4' and it
stopped dead. I kept pushing and it finally went through. I was happy
until it actually came up into another downspout. So, these 2 were T'd
together ... not bad as one carries a water from a very small piece of
roof. So, I went in from that downspout and the hose went about 15 or
20' and stopped. I couldn't get it any further. So, I started
investigating on the internet and made a few calls. An auger would
definitely break the plastic pipe, so I found a company with a jetter.
The jetter is a super high pressure nozzle that sprays forward and also
backward. They were able to clear it. Previously, the drain would
overflow with the water from a garden hose. His jetter pushed out about
6 times as much water. However, about 15' in, he noticed there was a
semi-blockage. He suspected that the pipe was crushed. As he didn't
bring up and soil, he didn't think there was an actual hole in the pipe.
We did, early on, have many truckloads of dirt brought in. That may
have crushed it. Or even maybe when the house was built. The drain now
takes water, however, on heavy downpours it will overflow a bit. So, we
have to dig and replace the crushed section. BTW, the jetter guy
charged $150. He said it would be about $150 - 200 to fix it depending
on if there were multiple crushed pieces. There are companies that
sell jetter hoses and nozzles that you can attach to a power washer. I
think with the number of these drains going from my house, I am going to
invest in it. I already have the power washer, so for under $200, I
could get everything I would need. Of course it wouldn't be like the
one the pro had. His pumped about 7 or 8 gallons per minute at about
2500 PSI and was mounted on a trailer. My pressure washer, while having
about the same pressure, only does about 2 GPM. But it should help to
clear these lines of leaf and dirt matter.