Sink Drain question

We're replacing a vanity sink with a pedestal sink. The existing supply lines look like they can stay where they are, but the existing drain line from the vanity runs straight down through the floor and makes a 90 degree turn between the floor joists. The pedestal sink instructions show a wall mounted drain line that makes a 90 degree turn inside the wall. In my case, this would then make another 90 degree turn to run between the joists to the drain stack. My question is, is it ok for me to keep the existing vertical drain pipe and single turn, or do I have to run everything as pictured in the instructions, into the wall? I would probably have to play with the drain piping from the pedestal sink a little to make it run straight down after the trap.

Thanks,

Jim

If I follow your description correctly, you have or are proposing an illegal S trap. This is covered many times in many posts on this forum which you can research, but in general, you should have a P trap directly under the sink which would be connected with a slip joint to the drain in the wall. The drain also must have a vent which it does not sound like you have. Perhaps I do not follow your twists and turns correctly.

It makes no difference how many turns your drain has, it will still be improper and "illegal", as long as it does not have a vent. The instructions do not show your drain setup because the company did not think anyone still used that drain configuration.

hj said:

It makes no difference how many turns your drain has, it will still be improper and "illegal", as long as it does not have a vent. The instructions do not show your drain setup because the company did not think anyone still used that drain configuration.

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This is an old house, and with the walls down for new backerboard and tile, the bathroom shows no indication of any vent stacks in either the toilet or sink walls. When I initially called the township and described my renovation, I was told that as long as I was replacing the new fixtures in exactly the same places as the old ones (which I am), I didn't need a permit. I did some research and have discovered that it is common for older houses like mine not to have venting. My plan was to re-use my original toilet, put in new tile, and add a new sink, NOT to re-plumb my house. What are my options here, realistically?

The only way you can be grandfathered is if you do not change the way the drain was configured originally.
If you change it, it will need to meet current code and will require a permit and inspection.

cacher_chick said:

The only way you can be grandfathered is if you do not change the way the drain was configured originally.
If you change it, it will need to meet current code and will require a permit and inspection.

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So if I put in another vanity style sink and use the existing drain pipe, I'm good to go, but if I want to replace it with a pedestal sink, I have to get a permit, install venting in this first floot power room and somehow get it up to the roof, get a permit and an inspection? I'm starting to rethink my plans here.

IF you can keep the drain the way it is, then you can use the pedestal lavatory.