I am remodelling a shower in my basement. The showr currently has a 2" galvanized vent that emerges from the slab and ties in to the vent stack for upstairs bathrooms. This existing shower vent is about 18 inches downstream of the shower drain, and 18 inches further downstream the drain line it enters the 4" sewer line right at the main vent stack for all three toilets in the house. My question is, do I need this shower vent, or will the toilet vent stack 3 ft away be sufficient? The existing 2" pipe comers right up through where I want to put in the new shower, and is rusted to boot.

There are good plumbers on here.

It would help to show a diagram or pic.

Depending on code and a host of other reasons, getting rid of a vent is not really a good idea, unless you can somehow ensure it is adequately vented in another way. You should not count on the 4" stack for your venting because in this case, because it sounds as though you would have one or more other appliances draining into it from above - then it cannot be used as a vent. Wet venting is possible, but that has considerations applied to it.

Post a pic, or a diagram so that the pro's here can help better.

What area do you live in? Do you know what plumbing code you fall under? Perhaps in your area a shower vent's mndatory. In the meantime most basement bathroom baths go down like this. Toilet connects to sewer main or the stack vent. Lavatory connects to toilet drain and runs a vent off the top the stubout tee out the roof or revents back into a dry vent in the attic.. The toilet wet vents through the lavatory vent and the tub/shower connects to the lavatory drain and is wet vented by it. This is a normal rough in and is acceptable both by local and state codes and also The Standard Plumbing Code Book in 90 percent of the country. Check your local codes to make sure you're not in the excluded 10 percent.. The vent off the lavatory may be run out the roof or revented back into a dry vent in the attic. Good luck and thank you for rating my answer. Tom