Connecting addition into existing DWV?

[scatkins]

I'm planning for a home addition where I'm going to add one possibly two new bathrooms.

This is all single story on slab. 45 year old house. All of the underground is cast bell and hub. I've done recent remodeling and mods to the DWV in two the bathrooms and the existing DWV seems to all be in good shape.

I'm trying to develop my plans keeping in mind how the new addition will tap into the DWV.

So here is my question to those who have done major construction add-ons: How is this typically done?

I'm assuming that a major addition such as this should be "spliced" in on a relatively large diameter part of the DWV. I'm thinking of routing the DWV from the Addition (which will probably be toward the far end of the house) around the structure and splicing in somewhere between where the existing DWV exits the house and the sewer hook up.

This would seems to me to be the best chances of having all of the old and new DWV performing well.

An alternative is to find an existing toilets and modifying the DWV in that region (all to code of course). However given that everything is under slab, it seems that could be a major easter-egg hunt. I speak with a bit of experiance as I've already dug under the slab a couple of times in previous remodels. It is very time consuming work. I can only imagine what the cost would be when I use hired trades to do that kind of work.

THoughts on the issue are appreciated.

STeve

 

[Cass]

That (outside run) will be your easiest / best / least expensive bet but you will need to find the depth of the existing line to see if you will have enough fall / pitch from the new bathrooms to the existing outside line. Are you on city or do you have a tank?
You may find you have to go further away from the house than planned in order for it to work. How far on the inside is the new bathrooms from the nearest existing one.

 

[Sponsor]

 

[hj]

dwv

Adding two toilets to an existing system that already may have two puts you at the mercy of the building department, which could require that the pipe be increased to 4" at the point where the load becomes 4 tollets. In that case going around would be the least disruptive since it would be easier to increase the pipe from your connection to the sewer tap at the lot line, than to cut the floor and increase it inside the residence. If they used logic and did not require the increase, then connecting to a toilet location near the perimeter of the building would require minimum floor cutting, assuming the depth is adequate for the distance involved. Although a good plumber can figure out how to install it in a very shallow method, even if it means changing the bathroom layouts.

 

[scatkins]

There will be an elevation difference between the addition and tap in points so that shouldn't be a problem. Sounds if my life will be best if I go the outside route. Got a few sidewalks to rip up, but that is a lot simpler than dealing with the slab. And it will probably work a lot better any way

Thanks

 

[hj]

drain

Actually the best solution would be to get a plumber and let him decide the best way.

 

[scatkins]

hj,

I agree, and that will happen,

but... at this point I'm just trying to do my homework in advance so I know the issues.