Is it possible to pass a 2" PVC drain pipe under the slab?

I cut opened a 4" wide trench about 8' long to pass a 1/2" PVC pipe from the wall to a kitchen island. Just as I was about to close off the trench my wife asked if it's possible to have a sink in the island...
The island is about 7' from the wall, the trench is 8' long to that wall. The nearest drain line that is open and accessible is the utility bath room which I do have the slab cut open and the 3" drain exposed.
I am contemplating running a 2" PVC drain from the island to the wall (this is not a problem as the trench is already cut and open), now once I am there at the wall, the utility bath drain is 7 feet away and the pipe has to make a turn to the right about 22 degrees.
So my challenges are:
Can I really pass a 2" PVC pipe under 7' of slab? I don't want to cut the slab open. It's mostly sand under the slab down here in Miami, If I do, I have to do it from the utility bath end and hope that the pipe will appear at the end of the trench where I can put in a 22" elbow. The problem I see is 7' is a long distance to bridge, and since I am starting from the utility bath end (downstream) it will be tricky to maintain the proper slope as I get the pipe through.
Even if this all work, the run will be 8' + 7' = 15' to the tie in to the main line and no venting. I could vent the pipe at the wall and run a 2" vent up to the attic and tie in with another vent stack but even that is not to code as code calls for 5' maximum vent distance. Someone told me I could use a studovent? (spelling) how does that work? Does it apply in my situation?
MC
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On Sun, 30 Nov 2008 23:54:08 -0500, "MiamiCuse"

Across the state from you, same sand, I shot a 2" 22 feet under my garage and hit a 1 foot square hole. Just be sure you have a good trench with a straight shot to work from. You also need to get the pitch right so you have to start deep and shoot up. I made a drill head from a rounded 2" cap with a 5/16 hole in the middle and three 3/16" holes around the edge 1/4 in from the edge. Make up a 2" to "hose" adapter for the other end off of a 90 adapter and about 2 feet of pipe as a lever.. Hook it up to the garden hose, Turn the water on and start shooting while you twist the pipe back and forth with the lever. It will go pretty fast and don't stop until you are through or the sand will pack back in and stop you dead. If you go fast you won't wash a big cavity under the slab.
BTW for our northern friends, I doubt this works in anything but sand.
The Studor vent is between you and the plumbing inspector. Some places hate them, others are OK as long as you have a real vent on the stack you are tying into.
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wrote:

How did you attach the garden hose? Did you do a 2" to 3/4" female adaptor and connect the hose to that?
The problem I see is since the hole in my slab is about 40" wide, and I need to span a 7' space under, I will not be able to put all 7' of pipe in the right position (under slab and pitching up) to start with. I will have to do 4' of it and then once all 4' are in, I will then have to take it all apart, then glue a 2" coupler, then glue another 3' of pipe and reconnect everything and continue again.
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wrote:

Yep I used a brass 3/4 NPT to hose adapter, just so I could reuse it. The PVC parts are going to be trash.

That should work, just cut the pipe a few inches from the elbow so you have some pipe to glue to and splice in the extra pipe. With only 4' in the ground you should be able to get it going again. When you get it through cut off all the extra stuff and hook up your riser for the sink and the lateral to the sewer. Just be sure to keep it pitching down. Here is a picture of the actual drill head I used, notice I left a stub of pipe for another coupling, in case I need it again.
BTW a cable saw is the easiest way to cut a pipe in a hole but a piece of nylon string will usually work.
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On Dec 1, 1:38 pm, snipped-for-privacy@aol.com wrote:

That looks good. I think I will do the same. I wonder if instead of a 2" cap, I go from a 2" to a 1-1/4" reducer then from 1-1/4" to a 3/4" reducer with a 3/4" cap. Drill a hole at the end of the 3/4" cap, and three holes like you have it on the 2" side wall, whether it will make the drilling easier since it will be a "sharper" drill, or may be it will not.
Here is a picture of my layout:
http://i173.photobucket.com/albums/w67/143house/trenching.jpg
On the upper right corner you can see the magenta shaded area that is the area the slab is currently opened and assessible. The thick blue lines are the finished PVC drain configuration for that bathroom.
Further south is a 4' wide hallway then the kitchen. Inside the kitchen is a 7' 6" long narrow trench about 4" wide also cut open. The southern tip of that trench is where the 2" drain needs to starts. There is no way I can start from the kitchen side. I have to start from the bathroom side and go at a 45 degree angle and pass through the narrow trench on the kitchen side, and there I will put in a riser to vent and tie into a pipe that will run south to the island.. The good news is I know what height that pipe needs to be at on the bathroom side, it has to be at least higher than the 4" drain right there. The bad news is I cannot see how I can maintain a pitch up as I push through so it ends at a particular elevation when it emerges under the narrow trench. Seems it would be very tricky and I might end up just below the slab leaving no room for the 7' 6" run to go "down".
I guess my question is, once you make it all the way through and can see the pipe on both sides, is there any chance there may be room in the sand you can "finess" the elevations of the pipe by moving back and forth to arrive at a more desirable pitch? My common sense tells me no not for something as big as 2"?
Thanks!
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On Mon, 1 Dec 2008 16:18:09 -0800 (PST), snipped-for-privacy@hotmail.com wrote:

I have shot a lot of sleeves under driveways. We always use a full size cap (actually bigger than the pipe) so you can go fast. The problem isn't washing a hole in the sand it is not washing too big a hole. Personally I would take a straight shot from the back corner of bathroom 4 to the hole in the kitchen skipping the dog leg in the hall. Just get your navigation right so you shoot in the right direction.
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For 7 feet and 2 inch pipe in sand I would use a shop vacuum instead of water.
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After thinking about it I decided to take your advise and do a straight shoot. This increase the overall reach between the two spot to about 12'.
I started off and drew a straight line from the slab opening to the target hole. The tricky part is not the direction horizontally but vertically. The main line is about 8" below grade, I figured over a 12' difference, at a minimum slope of 1/4" per foot, I need a three inch drop between the two points at least. I then dug down to the main line and created a sand trench. Then I used a 2x6 piece of lumber 4' long and laid it down to exactly how I want it with the proper slope, the pipe will be angled up the ramp as I drill through, I don't know how else I can maintain a proper up-slope.
I then did the assembly for the PVC pipe. Since my slab is only 5.5' long, I cannot position a very long piece into the trench, I must do the drill/cut/glue/drill more deal.
I put a cap on the 2" pipe, cut the holes the way you did, I used a stepped drill bit and that was really nice. Then I cut the pipe to 5' long, the most that can fit into the trench. Then I glued a 2" santary tee at the end. One end connects to the 5' pipe, the other end I glued a reducer to 3/4" and then a hose adaptor and my garden hose will come in from there. I then glued a short section (6") to the top of the tee, and capped that off. This short section is to be used as a leverage handle to help me push the pipe in. I also added a shutoff to the garden hose so I can turn on/off right there without needing to run back to the hosebib.
Now this is where I ran into complications. First I was not able to lay the pipe all the way down as I had two copper piping across the path, they made it not as easy to push the pipe along because I can squeeze through the pipe but with the handle contraption at the end it's stucked. I finness and finness and was able to send about 4 feet into it, the trench pooled a bit and I had to let it drain down with the hose shut off.
Now I need to saw off the end, and glue another 5' of PVC pipe with a socket coupling to continue...so I stopped because I started to wonder if this would work.
First, without being able to send in the whole pipe in one shot due to it's length, and had to use repair couplings, I obviously cannot prime/glue the joint, wait 15 minutes and continue. These joints take a few seconds to dry, but take up to 24 hours to cure. Usually with PVC it's not a problem since it's not under pressure and we can always leak test them. But in this situation, I will be twisting the PVC pipe and the joint will be subjected to torsion, and if it takes 4 sections of pipe with 3 joints, me twisting on one end will be passing that torgue through 3 joints to the drill head. I wanted to wait 24 hours for the joint the cure to have maximum effect. After all, if it does bust loose I can't tell until it's too late.
My question is. in this case where a joint is necessary, what is my best shot to prevent it from busting loose or partial leak? There is no leak test possible? or I need to plug it at the low end when done, fill in water on the high end with a garden hose and let it sit in pipe and see whether it go away?
What would be the best joint I can make? I know the 1-1/4" pipe has long coupling and short coupling. 2" pipes seem to have only short couplings, unless there are long ones I can special order. I also wonder, if I should just put in a 2.5" banded fernco coupling ON TOP OF the PVC coupling just to give it additional rigidity and torgue resistance as I drill?
I may be over thinking this but this is a one shot deal, if it fails I am done I may not be able to back things out especially if the joint busts and I can only back out one end of it.
Thanks,
MC
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you can buy flexible pVC pipe in a variety of sizes. Stumbled onto it when shopping for clear plastic PVC schedule 40 pipe for some kids games I was building
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I suggest you re-think this process. The pipe is very likely to sieze if the soil is allowed to settle around it. Water washing is generally done in one continuous process. If you have to stop and start you would be better off to use a mechanical drilling system of some kind.
Don Young
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wrote:

Once you get the kitchen end stubbed up make it a bit too long and put a cap on it. Use the hose adapter to pressurize the pipe again to full house pressure (there should be some air in there now to compress). Shut off the valve and leave it overnight. Crack the hose joint open in the morning and see if it is still under pressure. Better is to put a hose to hose Y splitter on it and a gauge. Pool piping is tested at 30psi but you should hold more than that.

They should have the deeper socket Sch 40 connectors at Home Depot. The 3/4" socket ones are DWV (drain). Use the blue "wet dry" glue. It sets up a whole lot quicker. I would still give it an hour.

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clipped

Somewhere in Indiana there is a yard with about 10' of garden hose buried.

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