Drilling an underground pathway for a pipe using a garden hose


I read that you can hook a PVC pipe to a garden hose then be able to pass that PVC pipe under a driveway. I have done that a few times and with the sandy soil in south Florida it does not take very long. In the past I have done that only with small diameter pipes 1/2" used for sprinkler lines under driveways about 6' wide or so. The fact that it's a sprinkler pipe under pressure also makes it easier because I am not so concerned about the slope of the pipe or whether there is a belly in between or not.
Now, the problem is more complicated. I want to pass a 2" PVC pipe under the floor slab from a bathroom where the slab is already cut open, 15 feet across to the location of a future kitchen island.
The fact that it is a 2" pipe makes it more complicated. The fact that it has to be sloped property being a gravity drain pipe also makes it more complicated, and lastly, since the opening in the bath is along about 4' long, I have to feed 4' of pipe in each time, gluing a new coupling.
I did this by gluing a 2" cap over the end of the pipe, then drilled a few small openings, on the other end I glue in a 2" to 3/4" reducer, then a 3/4" MIP to 5/8" adapter, then the garden hose. When water is turned on, it fills the pipe then I started to push the pipe in. I did this and it was able to get about 6 feet in and then stopped. Does not matter what I do it will not advance.
Finally I decided to measure where the end of this 6' in and cut a small opening in the slab and dug down, and guess what I found, a single piece of coral rock within the sand blocking the path...the rock is small, about the size of a computer mouse. I dug it out and now I am ready to continue.
But before I continue, I am wondering if I may run into additional rocks in the 9' ahead of it, and if I do, I don't want to cut an opening in the slab every time it is stuck. Because I am using a 2" pipe with a 2" cap, the pressure of the water coming out of the front is fairly low. I am wondering if I should cut that cap off and glue in a reducer from 2" to say 3/4", and close with a cap and drill a real small hole at the end say 1/4" in size.
I am thinking being a smaller hole with a smaller diameter pipe in front would give it a higher pressure jet in the front that may have a better chance of dislodging any rocks should I run into any again. But I am not sure if making it easier for a smaller 3/4" section in the front to go through would necessarily be enough to get the bigger 2" that follows.
So the question is should I stay with the 2" cap with three nozzles or fit in a small section of 3/4" with a smaller nozzle. I can access the front of it from the hole I cut, but once I pushed forward and glue in more pipe from the tail end it will be impossible to change the head.
Thanks in advance,
MC
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Why not?
Making a small but repairable hole beats the heck out of tearing up the whole slab.
The "access ports" will help ensure you have the proper slope.
Only problem with that approach is that you don't want to excessively undermine the slab with your "drill water."

Well, with "water boring" you can only dislodge a rock if you also wear away some space for the rock to fit into. Indeed, that's a major problem with your technique: you may well be setting up your concrete slab for failure the next time a heavy truck come in.
Frankly, a good case could be made for "doing it right the first time" and just cut out 8" of your slab; dig out the soil and regrade with select material; lay the pipe in place; fill with select maerial; and patch the slab. Once you have an opening you may want to put in a larger drain and, perhaps, run some conduit for future use and, may, even some water pipe.
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MC-
I would totally agree with John G's post. The technique used for a pressurized small diameter pipe is a bit less forgiving for a large diameter gravity line. Small rocks can be easily dislogded or large rocks at can be jogged aside for a small pipe. Large rocks are a problem for large pipes.
Undermining slabs can cause them to crack in the future but indoor slabs are much less of a problem but can still be a problem with hard finishes.
cheers Bob
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I don't want to cut the slab. To me it's more important to preserve the monolithic nature of the slab then the compacted sand under. Majority of the load is on the footings, it is not uncommon in our neighborhood to open up concrete slab and see the sand already sitting an inch or two below.
If I cut a long trench I have to drill rebar dials and tie them and put moisture barrier seal retreat with termite layer etc...plus this is going under a hallway into the kitchen so trenching is difficult with two walls in between.
MC
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I am wondering if I should cut that cap off and glue

First off your pressure inside the pipe is constant regardless of the diameter of the pipe.
You have a volume restriction first where the garden hose is connected and then where you have the holes drilled into the cap.
To increase the pressure, you need a pump.
I would continue with what you are doing to see if it works, if it does fine but if you want to try increasing the pressure I would feed the pressure washer hose and nozzle inside the 2 inch pipe, and then figure out a way to mount it on the inside of the 2 inch pipe so the output would spray forward.
This way you can twist the pipe to selectivly blast the water where you want. The dirty water then has a free flow back through the inside of the pipe and might give some clue to what you are blasting against.
The big problem as I see it is maintaining the proper slope for the drain pipe once you are done. Left to its own devices over time your pipe is going to sag if nothing supports it properly. 15 feet in the blind is a long way to go.
--

Roger Shoaf

About the time I had mastered getting the toothpaste back in the tube, then
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Roger Shoaf wrote:

He's not thinking pressure but he's meaning velocity.
Smaller holes-->higher velocity
But, you're right his high volume pipe full of water is a problem that could probably work better w/ a rig-up like you describe.
I'll admit I've not tried if for anything sizable but I know it's done fairly routinely w/ much bigger but w/ specialized rigs.
Not sure where the other end is going; I'd be tempted to take the bucket-mounted posthole driver and turn it horizontal and try to drive that sucker from the outside...
--
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Wow, a mind reader! Say, what color am I thinking?
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Good idea. I would not have thought of a coaxial arrangement like that. I won't be a mind reader and tell you what you were really thinking.
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Stormin Mormon wrote:

Isn't that used for high colonics?
TDD
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Hmm. I guess that's possible. I seldom give much thought to the darker parts of a person's body.
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Stormin Mormon wrote:

Like the bottom of their feet?
TDD
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MiamiCuse wrote:

I installed a number of PVC well points using 2" PVC. According to the manufacturer, I used A 2" coupling and 2" to 1" adapter and a "T" allowing me to attach 2 garden hoses to the 2" PVC on the feed end (For greater flow). The other end was modified by cutting "teeth" into it with a saw. The teeth were 1/2" triangles. Turn on the water, and feed the pipe into the ground, rotating it back and forth to aid the cutting action with the teeth.
Perhaps use a coupling on the end, and form the teeth on it, to make sure the hole is big enough for the couplings.
Be prepared for lots of water coming back with the sand. You'll probably need a pump capable of pumping a sand slurry.
Or, start with a 1" pipe, and run it through to your hole outside, then run the 2" PVC (Get a 20' length at a plumbing supply store) over the 1" back into the house. The 2" will slide over the 1" as a guide. Bevel the couplings (Before you glue) on the 1", and the inside of the 2" so it doesn't catch at the couplings. Then pull the 1" out of the 2".
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If this is for a drain line, as I think the OP indicated, if the slope is going upward, as long as the input from the island is higher than the connection point into the existing drain, it will work. There will just always be some water in the drain line, but that is no different than if there was (and should be) a trap to prevent sewer gasses from coming up the line and into the kitchen, The reverse slope might make the line a little more prone to clogging, but a 2 inch drain is not likely to clog unless you put some very large stuff down the drain.
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hr(bob) snipped-for-privacy@att.net wrote:

Does this in some way relate to my response?
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On Fri, 25 Sep 2009 13:47:27 -0700, MiamiCuse wrote:

Haved you considered using a heavy duty shop vac attached to a 5 gal. plastic bucket to catch the sand. I've put fence posts in, in this manor in Florida. Sure would keep all the water out of the house. Of course the further south you are the more coral you find. Pinellas being just a sand bar it is easy there.Dade is known for coral rock.
Just a thought.
__________________________ suction |Shop _________ _____ Hose attaches here |vac | |bucket | | | | | | | | | |_____| |_______|
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On Mon, 28 Sep 2009 12:58:25 -0400, RLM wrote:

Might copy and paste diagram to a text editor such as notepad.
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