Hello!
Just got my blocks laid for a new garage addition to my home and need to make sure I am on the right track. I had initially planned to have the plumbing rough done by a plumber but after contacting 6 "respectable" plumbers and getting no interest I have decided to tackle this myself. I had planned on doing the finish work but I wanted the reassurance that the under slab work was done correctly. After scouring the Internet I think I have come close to the correct layout for my rough-in.

I am in Arkansas if that matters. This addition will have a new sewer line run to the street. It is 80 foot from the sewer manhole and the addition is 40 feet deep. I have attempted to make a diagram showing what I am looking at doing. This shows only the overhead view of the planned rough in that will go under a 4" slab. The upstairs will be another thread!

I have a few questions:

1) I plan on using a 4" pipe for the main line. Is that big enough? Do I have to go 4" from the sewer to the back of the addition where I will terminate it with a clean out or can I reduce it down to 2"? I think I know the answer but just curious.

2)I will have 3 90 degree elbows that will come down into 8" blocks and out. I am also filling the block so I have to get this right the first time. Any things that those with experience might be able to warn me about? Or tips on getting it right?

3)Do I need to run a vent before the clean out or is having each drain vented good enough?

4)Is 3" good enough for the pipes coming down from the upper level?

5)Is 3" good enough for the toilet on the slab?

6)Once I start going up into the walls and into the attic can I tie some of the vents together assuming I don't reduce the size? Not a big deal at this point in the construction but just curious.

I know this is a lot of questions and I purposefully tried not to use to many plumbing terms as I am sure I would screw them all up and sound like even more of an iggy than I am! Apologies in advance if I have left out any info that is required to get an accurate impression of what is planned.

If anyone needs help with Linux or Arcade stuff I'd be glad to help but when it comes to plumbing I am quite helpless!

Thanks in advance!
T

1) I plan on using a 4" pipe for the main line. Is that big enough? Do I have to go 4" from the sewer to the back of the addition where I will terminate it with a clean out or can I reduce it down to 2"? I think I know the answer but just curious.
A 4" main is standard. Run 4" all the way.


2)I will have 3 90 degree elbows that will come down into 8" blocks and out. I am also filling the block so I have to get this right the first time. Any things that those with experience might be able to warn me about? Or tips on getting it right?
This is not clear and not shown on your diagram. Will these 90's be vertical or horizontal? Could you use short sweeps instead?

3)Do I need to run a vent before the clean out or is having each drain vented good enough?
A vent on the CO isn't needed.

4)Is 3" good enough for the pipes coming down from the upper level?
Yes, a 3" main is acceptable for upper levels.

5)Is 3" good enough for the toilet on the slab?
No,we use 4" for the main and toilet drains under the slab.

6)Once I start going up into the walls and into the attic can I tie some of the vents together assuming I don't reduce the size? Not a big deal at this point in the construction but just curious.
Yes you may. This is called "reventing" However, the drawback to reventing back to one roof vent is that if you ever have to snake out a individual vent you will have to cut it free and work in the attic.

I can find no fault with your layout. Since the shower will be wet vented by the vented drain,(a lavatory vent?) there's no reason to vent the shower.

Good luck, Tom

...Will these 90's be vertical or horizontal? Could you use short sweeps instead? ...


Thanks for the great response Tom!

I have attached another crude pic. The blocks are 8" and I will be coming down into them in three places. 2 3" and 1 2" elbows I assume. Is there any other way? I will have to bust out a hole to get them in. Anything I need to worry about?

T

These 90's will be at the base of the stacks and are perfectly acceptable. Your only other option would be to run them outside the block wall and fur the wall out. Regards, Tom

5)Is 3" good enough for the toilet on the slab?
No,we use 4" for the main and toilet drains under the slab.



Another question.

What size does this vent need to be? 4" or can I get away with 3"? I doubt less though right?

Thanks!

Another question.

What size does this vent need to be? 4" or can I get away with 3"? I doubt less though right?

Thanks!
Code calls for one 3" main vent. All the rest can be 2". Cheers, Tom

Tom you ROCK!

Another question. I know I need a licensed plumber to do the connect at the street. I happen to have a manhole directly in front of where I will be running my main line. One of the 2 plumbers that actually came on sight acted happy that it was there. Curious I popped the cover off and inspected. Its deep and only has one inlet and one outlet where it takes a 45 degree turn. My original tie in is down flow from this manhole and across the driveway so it is not feesible to tie in there. My question. Where should I plan on digging my trench too? The manhole or should I shoot for tieing into the inlet that I see coming into the manhole? I am confused if it is allowable for my pipe to come into the manhole or if it has to connect to the pipe before it gets there?

I'm not sure I understand the question. Each parcel of property has a sewer raiser that's dedicated for the sewer connection. If I understand you correctly you don't wish to use your present one. You will have to contact the building department to find out what options you have. Let me know what they say. Good luck, Tom

When he was out here inspecting the footing I asked the inspector and he said it was not a problem to tie in again. He just stated that I could not do it myself and that I would need a licensed plumber.

My only question is where do I run my trench? Can a plumber drill into the manhole and have my pipe coming out of the side or do I need to find the line that travels between the manholes?

I only ask because I am not sure why the plumber was pleased that the manhole was there. He acted like it was going to make his job easier. And now that I think about it the other plumber that came out measured from the manhole cover to the addition so it gave me the impression I could just come into the manhole.

Sorry if this is a dumb question but I am just really curious. It would seem that it might be easier to call the city inspector but from my experience he is hard to get in touch with.

Either way the depth of the manhole gives me plenty of slope to work with so I am happy!

My only question is where do I run my trench? Can a plumber drill into the manhole and have my pipe coming out of the side or do I need to find the line that travels between the manholes?

If the city lets you a hole can be punched in the manhole and you can run to that. You don't slope to the sewer elevation. You slope the sewer line 1/4"to the foot and 45 down to connect to the city raiser. Too much slope and the water runs so fast the solids drop. Too little slope and the water won't move the solids. If they let you connect to the manhole the hole will positioned where your sewer line ends so you shouldn't have t worry about connecting to a city raiser.

Sweet. I will call my inspector and ask him. I figured out after I last posted what a raiser must be. I assume though that the city will let me because the inspector stood right there when I asked him and all he said was a plumber must do it.

Thanks so much for your help. This is by far the best plumbing resource I have found on the net!

"This is by far the best plumbing resource I have found on the net!"

Music to my ears! Thank you! Thank you! Thank you!