Venting bathroom expansion

Hi everyone,

I am currently looking at adding a shower stall to a half bath. In order to do this we have to move the toilet to the other end of the room and put the shower where the toilet was. The new toilet location is where the clothes washer is currently hooked up. There is a second washer hookup just outside the room that we will be moving the washer to. The new toilet location will put it 11' from the main vent. I have had two plumbers come out. The first didn't look in the crawlspace and just quoted $400 a fixture, for a total of $1600 to rough in the bathroom. I am very skeptical of this figure as most of the plumbing is already there. Mainly the two drains need to be swapped and one hot water inlet needs to be moved. A second plumber came out today and wouldn't give a price unless we agreed to go with him as he wouldn't be able to start for 3-4 weeks and didn't want to waste his time coming up with a bid. He wanted to remove the entire dwv lines and replace them with PVC, they are currenlty cast iron. He said it would take about 1.5 days.

I have done much research on this and am tempted to do it myself as me and my husband are both quite handy and I have helped plumb my parents home when they built it a few years back. The biggest concern I had was the venting as the toilet would be beyond the critical distance from the vent, the other three are within the distance. The plumber today mentioned putting an automatic vent under the vanity sink. What is this? I know my area is governed by the national codes. I have called the code enforcer to see if I needed a permit or anything and he told me "if you don't change the roof line, I don't need to see what you do". I have attached a rough sketch of the current configuration of the room. Is the plumber that came today on the right track of recommending that all of the cast iron be removed and replaced? How much should I expect to pay for this and how will they get the cast iron from under the house as it runs underneath for about 15 feet and at places is even buried. Any input on this would be greatly appreciated. We have a third plumber coming out tomorrow to do an estimate but I am not sure what is reasonable. Thanks!

DIYgal

IPC or UPC code

i'm not a plumber, so I'll just tell you what I know and let others take it from there.

You have to know whether your code is UPC or IPC or a variant of one or the other. The toilet being on a 3" pipe can be far away from the stack but the maximum as per code depends on whether you are under the stricter of the two codes. The farther a toilet drain goes unvented, the more the whoosh when it finally gets its head of water running. Toilets are all designed to refill their P trap too, so the main drawback to being unvented is lessened a bit.

The auto vent thing is an AAV. Not a bad thing, but not a good thing either if venting as a whole is not up to par elsewhere. In other words, it is not recommended unless you already have planned for a lot of real venting, and then you find that in one place it is a quick fix. There is one situation where it is the only solution: in a kitchen island sink.

Congratulations on coming here for help in building your plan.

david

drains

What you have now is useless as far as the new layout is concerned, but the only thing that has to be changed to PVC/ABS is the new piping. A per fixture price CAN be good for you depending on whether or not he intends to "add on" if he encounters unforeseen problems, or good for him if it becomes an easy installation without problems.

i think your plan will go like this: Distance from toilet to first vent will be roughly where the sink vent is now. Without cutting into the roof to add a new vent, you can draw a second vent off the first one.

david

Can't really make anything out of your sketch. Is there a vent for that washer? AAV can be troublesome, but are allowed by codes in some places. From the feedback we hear on this forum, some places allow virtually unrestricted use of AAV, and some inspectors only allow it as a last resort, if proper venting is totally impractical.
As for the cast iron, it will usually be abandoned in place. I recommend plugging all exposed ends with a fistful of concrete patch to prevent intrusion of critters.