dvw diagram bathroom addition

I'll be tying into an existing 4" drain through the cleanout. This is in rural area with septic system with a pulled permit. The new bathroom will be roughly 8' by 8'. Some questions I have:

1. Is it okay to tie in to an existing cleanout? It's a straight 30 foot run directly to the septic tank.

2. Is it okay for the toilet riser to be about 20" like that?

3. Any problems with how I've had to extend the CO down the crawlspace? It gets to be 18" high down thataway.

4. Do the vents look okay?

5. How in the heck do I wet test this thing? There's no way I can fit in a test y because of where the new WC is going. I guess I could take off the existing toilet and stuff a test ball down there, trying to get it to work back up the 4" pipe a little? Maybe since this is a rural area about an hour from the county, the inspector might not require a wet test. I'm going to call and ask tomorrow.

Thank you all so much for being there!

IT looks like a good DIY job. I, personally, would not use 1 1/2" pipe for the sink drain, and WOULD have a cleanout under the sink's tee, (especially if the drain line is 1 1/2"). You do not have to make the test ball go backwards. Just get a "long one" and shove it down into the pipe, then inflate it.

Thanks HJ. I used the 1.5" because there's an old vent in the crawlspace that probably hasn't been connected since this 110 year old house was plumbed! I capped it, but the UPC allows for the 1.5" so I can use it, but if you think the 2" is so much better, I'll consider a wye into the tub drain.

I'm going to use a dual stage test plug through the old wc.