Latest Discussions : Plumbing


01:47PM | 08/31/05
Member Since: 08/30/05
3 lifetime posts
I am in the process of renovating the pantry in my CIRCA 1860 home. While tearing out the deteriorated plaster and lath, I exposed the plumbing for the upstairs bathroom as well as that for the pantry. None of the existing units are vented, and I wanted to see about upgrading the system.

Here is what I have:

Upstairs (and currently accessible from beneath the floor) I have a sink with an S-trap and a tub. The sink waste line (after the trap) drops through the floor then takes a 90degree turn into a 1.25” lead waste line. That line disappears from view through adjoining floor joists, but I presume it meets up with the main waste vent stack several feet away. The tub is similarly plumbed into a 1.25” lead horizontal waste line, but at some point the original trap was replaced with a drum trap. Both of these fixtures recently required snaking to improve performance, but both are currently working well. The tub is only used for showering, so I don’t know if siphoning would be a problem. The sink does not appear to siphon even when filled and drained all at once.

Downstairs in the pantry, and directly below the two upstairs fixtures, I have a waste line for a clothes washer and plan to add another for a sink. The washer line is not vented and drops through the floor for an in-basement p-trap connected to another part of the waste line.

My questions are:

1- How might I upgrade some or all of the fixtures (downstairs lavatory and washer, and upstairs lavatory and tub) to a venting system?

2- If the fixtures are working fine now, is this necessarily advisable?

3- Are the existing lead waste lines a problem?


1- Further tear-out upstairs is out of the question.

2- I do not have access to the main waste/vent stack on the second floor. It is buried deep behind chimneys and complicated wall partitions. If I abandon the lead lines, they will need to be plugged and left in place for the foreseeable future.

3- I believe the s-trap on the upstairs lavatory has to stay. The sink is on an exterior wall, which is filled with vermiculite insulation. I suppose I could run the “tailstock” as a strait shot through floor and put a p-trap below the floor, however.


1- Could I use the existing lead waste lines as vents? They are obviously lower than the flood stage of the lavatory and tub they serve, but could I resolve this issue by installing a check valve? I can easily lower the outlet of the tub trap by as much as 18” below the current waste line (made of lead). I could do the same for the sink if I wanted to use a really long tail stock and put the trap below the floor.

2- What about vents made for inside applications like the Studor Air Admittance Valve? The ones that act like a check valve for air, allowing it into the vent, but not out? Are they safe and reliable? Would you ever consider building them into a wall where they can’t easily be serviced? Might they at least be used for the downstairs fixtures?

Thanks for any ideas you might suggest.


04:36AM | 09/08/05
Member Since: 08/29/04
227 lifetime posts
I would not put any studor valve in any wall that will be inaccessible.

Your question is a huge one. Typically it would take someone on the site to give you an exact answer to your question.

Lead wastes should be replaced. If you rebury them inside walls and floors you would be making a mistake. In our company we always replace them when remodeling. Lead wastes have about a 70 year life span. Sometimes they last longer, but eventually they break. If you remove them while walls and floors are open, then you will not have problems with them after you've spent money re-drywalling and painting.

You really need to get either a book on plumbing remodeling or professional help to make some determinations on what you can and can't do.

Here's what we have done in the past, we have been able to drill a hole below a wall in the joist space to insert a vent into the wall, then go up into the attic and find the same space and drill a hole in the top plate. Once we get the two holes, we can use a flashlight to find out how far off they are from parallel and redrill so the holes are lined up. Then we can feed a length of pipe up through the holes into the attic. Once in the attic, we can retie to the existing vent system. Its a little more work than tearing out the walls in the bathroom, but it works. You can then open a small hole behind the sink and attach a sanitary tee to the pipe and drain the sink into it. The only patching would be behind the sink cabinet, which isn't usually visible.

Remodeling plumbing is usually one of the more difficult types of plumbing and takes a special type of technician who can find his way around dificulties and be creative. The average service and new construction plumber has difficulty with this type of conceptual thinking.

My advice would be to pay a professional to come out and give you some good diagnostics.

Good Luck

Raymond VinZant Plumbing Prof.


07:32AM | 09/08/05
Member Since: 08/30/05
3 lifetime posts

Thanks for your helpful reply. I've already taken some of your advice since posting my initial question, and I appreciate what you say about remodeling work requiring creative thinking. As it turns out, I've discovered that the UPC only allows air admittance (Studor) valves with an exemption from the local authority. My local code enforcement officer doesn't like them.

As you suggested, I've realized that I can probably finesse a vent through a second floor wall (at the end of the tub) and into the third floor. There I can tie in with the main vent. The branch vent will be exposed in that room, but so is the main vent (it’s my son’s bedroom so brightly painted pipes are ok – if not cool).

This will take care of the downstairs, and I can do the same for the upstairs tub, but I'm still stymied by the upstairs lavatory. It is situated on an opposite (exterior) wall, about 8 feet away from the new vent. It is also an old pedestal fixture with an s-trap. My understanding is that the UPC allow for neither horizontal wet venting nor for combination waste and vent runs (is this correct?). I’m worried that if I’m forced to vent vertically off this fixture the trap will freeze in the winter. The walls are only 2x4, without a vapor barrier on the inside and without house wrap on the outside. To make matters worse, the wall is insulated with vermiculite. Can I run a vent up inside an exterior wall cavity without risking my trap freezing? I was thinking of bringing the drain up through the floor under the sink and behind the pedestal, squeezing in a p-trap (trap arm 2x diameter), then as high as possible (but still behind the sink) taking the vent off at a 45 to bring it within the exterior wall. What do you think? How much of the vent above the trap needs to be inside my heated envelope to avoid freezing? (Maine, north wall)

Any thoughts?

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