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bauer09 · Jun 14, 2010, 06:12 AM

Hi There -

I have one general & one specific plumbing/venting question. The house I am working on was built in the late 40's -- the DWV system is very simple --- one main waste-vent stack all together. Looking through plumbing codes, it seems that this system is no longer allowed -- is this true? It is just one main stack going through the center of the house and terminating above the roof. It essentially provides all wet-venting for each fixture... which from what I understand is only legal if the fixtures are on the same floor.

So assuming that this is an incorrect way of venting by new standards, I am trying to upgrade the venting system in the house as I remodel each room. I am currently remodeling the kitchen, and I have the situation below:

The current trap is an s-trap that simply goes straight down in the basement, and straight into the main sewer line in the basement floor --- no venting whatsoever. I would like to fix that situation, but I have a problem with a window directly above it. There is a current vent line about 3 feet to the left of the current drain line (as shown in the drawing in grey). I could easily p-trap the kitchen sink and extend a vent up and over to that vent -- however that would require a horizontal section of venting, and the window prohibits me from making that horizontal line the required 6" above the flood level of the sink. What are the code-approved options in this case? I am wondering if I can make that run (as shown in red) using drainage fittings and 1/4" slope, then use a 90 elbow as soon as I get past the window, extend it up and then over to the vent -- as shown in red. Is this allowed by code in this situation? If not, then what is approved? I'd like to stay away from AAV's...

Thanks in advance!

massplumber2008 · Jun 14, 2010, 07:00 AM

Hi Bauer...

I would pipe it up exactly as you have it drawn... go up to just under the window and then run over to the vent pipe pitched as you suggested. When you connect into that vent stack be sure to install a sanitary tee fitting UPSIDE DOWN so water that flows into the vent system can drain naturally into the drain without resistance to the flow. Be sure that the sanitary tee fitting is at a minimum of 6" above the flood level rim of the kitchen sink.

No fixtures connect above the vent stack... right? Let me know...

Back to you...

Mark

bauer09 · Jun 14, 2010, 07:13 AM

Thanks for the quick response Mark --- that is correct, there are no fixtures above that point --- the vent stack goes straight to the roof.

As for the general question regarding old waste-vent stacks... am I seeing the big picture correctly in that everything is just wet-vented and they hoped for the best back in the 40's? How much trouble is it reasonable to go through to try and fix these problems? Some of the drain lines - like for the tub, are too far from the main stack to even consider the main stack a vent. Here is a basic outline of the homes dwv:

Just curious -- thanks again for your help, your answers on this forum are very helpful.

speedball1 · Jun 14, 2010, 07:21 AM

Another option would be to install, if local codes allow, a AAV(Air Admittance Valve) just after the trap. (see image) Good luck, Tom

massplumber2008 · Jun 14, 2010, 07:29 AM

I'm going to let Tom answer that Bauer as he was actually plumbing back then. Have a good day!

bauer09 · Jun 14, 2010, 08:11 AM

Ha just wondering...

Last question - when I make that turn to go around the window, once I get above the 6" above FLR, can I then use regular 90's? (as oppposed to sweeps.. )

massplumber2008 · Jun 14, 2010, 02:39 PM

These systems are certainly outdated, but if you aren't having any major issues then I wouldn't go changing too much... ;)

Once above the flood level rim you can return to regular 90s.

Mark

speedball1 · Jun 14, 2010, 04:35 PM

Typical 40's layout. Tubs had drum traps with no vents. Sounded like someone gargling in the next room when it drained.
I'm a great believer in " If it ain't broke, Don't fix it". If both bathrooms are working then leave them alone, however if you want to vent your house by code I can tell you. Mark has the skills to draw it out on computer but it's simple as running a new stack off the old one and redoing the drainage in both baths.
Interestesd?
As for your kitchen vent if anything's draining in that vent stack you're out of code and if it's a dry vent then fudge a bit on the 6" above the flood line thingy and run the vent.
If there's drainage in the vent you wish to connect the sink vent to then you might want to take the easy way out which is the AAV I suggested earlier. Anyhow the best of luck. Tiom

bauer09 · Jun 15, 2010, 04:51 AM

Thanks guys, that's what I thought. The kitchen vent is dry, so I'm going to take care of that. Not redoing any baths right now, if/when I do I'll reconsider the venting at that point.

Last question - and it goes along w/ the 40's layout --- if I had a 3rd floor finished area, right above the two bathrooms, where I wanted to add a small washer/dryer --- Could I just tie into the main waste stack to drain it? I mean, it's not built/being used as an actual dry vent, so I wouldn't think I'd be violating anything as far as that goes, right?

speedball1 · Jun 15, 2010, 05:27 AM

last question - and it goes along w/ the 40's layout --- if I had a 3rd floor finished area, right above the two bathrooms, where I wanted to add a small washer/dryer --- Could I just tie into the main waste stack to drain it? I mean, it's not built/being used as an actual dry vent, so I wouldn't think I'd be violating anything as far as that goes, right?

Why the heck not! (unless it will be inspected!) The ironic thing about it is that out of all the fixtures on that stack the washer will be the only fixture that conforms to code when it comes to venting. Good luck, Tom

bauer09 · Jun 15, 2010, 05:34 AM

Haha exactly what I was thinking. So if this was to be a code-approved and inspected job, the only way to go about it would be to go down and vent all the lower fixtures? Yikes.

speedball1 · Jun 15, 2010, 06:19 AM

Originally Posted by bauer09

haha exactly what i was thinking. so if this was to be a code-approved and inspected job, the only way to go about it would be to go down and vent all the lower fixtures? yikes.

Yes! This would be a major remodel job. But it could be accomplished if you had to bring the house up to code. Cheers, Tom