Replacing old Cast Iron Pipes that rusted through... are these other drains wrong?

[atomicdog]

I'm replacing the shaded section of this diagram. It is currently cast iron that has rusted through and I'm replacing it with 4" PVC. My concern is this... the drains for the sink and a washing machine that are attached to it... They drain great, they don't seem to have any venting problems, but I want to make sure that they are set up properly now so that I don't have to go back and fix this later after a home inspection or something. I know I need to replace the washing machine drain with 2" PVC instead of the current 1 1/2" ABS, so I'm already planning to do that. Does everything else look okay? Thanks for you help!



Helpful Plumbing Hints for Residential Construction by Bert Polk Plumbing Inspector Lincoln County

 

[hj]

Technically, NO, because the sink and washer drains will NOT be properly vented, and an AAV will NOT relieve the positive pressure caused by the plumbing on the upper floors when they drain, and your sink, as shown, will have an "illegal" S trap.

 

[Sponsor]

 

[atomicdog]

Dang it... I kind of figured you were going to say that. I'm curious, did the codes for this change at some point? The washer drain was an addition but the sink drain has always been there, it used to connect to a HUGE utility sink (but the drain was cast iron back then and was updated to PVC). I guess it was allowable back then (1940's) to have an sink drain connecting the way it is shown in my drawing?

 

[Jm66208]

I bet I could visit 100 older (30's & 40's) homes in my area & 95 of them would have the setup you have. Most are not original, and plumbed into the cleanout. I guess they just figured washers would empty into the floor drain back then. Or maybe everyone just went to the laundrymat. Not sure.
I should probably be horsewhipped for saying, but I've done a few like this (less the s trap and plus the AAV) for lack of a better solution. I even use a saddle-t to tap into the iron stack. Home inspectors either don't know, or look the other way, because it's never an issue around here.

Helpful Plumbing Hints for Residential Construction by Bert Polk Plumbing Inspector Lincoln County

 

[Jadnashua]

Venting requirements used to be a lot more liberal, but technically, it was still a problem. Basically, while wet venting is still allowed in a bathroom group (must all be on the same floor), it still would have access to at least one real vent. Your main stack is acting like a vent for everything, and the velocity of the flow from the pumped washing machine is likely enough to cause the sink trap on that line to be sucked dry.

Each trap should have a vent coming off the trap arm. You can combine them (there are rules about that), but those from the basement, would then need to go upstairs above the fixtures there before it could then join into the vent. Keep in mind, once a pipe is a drain, it is no longer a vent, and vice-versa. The rule is, vents can be joined at 42" above the floor OR 6" above the flood rim of the highest fixture, whichever is higher. So, at a minimum, you'd have to go 42" above the floor of the fixtures on the first floor, and if that pipe also serves a second floor, you'd have to go above that one instead (or run the vent all the way to the roof or attic).

Now, will it work as is? The laundry sink will probably have its trap cleared...the WM's trap will probably stay wet, but it won't pass code.

 

[Jm66208]

Just thought of another solution. Some older homes have a vented house trap. If it was in close proximity to the washing machine, you could tap into that vent. A finished basement would make this more difficult.

 

[atomicdog]

Thanks for your responses guys, I really do appreciate it. I figured the codes were just a lot more liberal way back when, and if there were no signs of anything ever being updated I'm guessing it would still be considered 'okay'. But, since I have to work on it now I'm in for the long haul!

So... what I was hoping to do is something like what I've drawn up here... but based on what you're describing jadnashua, I'm going to actually have to tie in to the vent BEFORE the above floor's waste. The could be a problem, that pipe that feeds up to the vent is really jammed up in to the joist. So this configuration I've drawn up here is not workable then?

 

[atomicdog]

Just thought of another solution. Some older homes have a vented house trap. If it was in close proximity to the washing machine, you could tap into that vent. A finished basement would make this more difficult.

Unfortunately this plumbing that I'm working on is on the back of the house and that is on the front of the house. Argh!

 

[Jm66208]

Unfortunately this plumbing that I'm working on is on the back of the house and that is on the front of the house. Argh!

"close proximity" was a poor use of words on my part. What I was think of was that many basements are partially finished, and access to the vent I described can be limited.

Also, nope, your second drawing wont work...sorry.

 

[atomicdog]

When you say it won't work... you mean I need to tie in to the vent above prior to the waste from the first floor bathroom, correct? I'm hoping that's the only problem I have left to solve at this point and the at the rest of the drawing looks okay?

 

[Jadnashua]

Unfortunately, no, that would not pass muster since the line you are tapping into is technically a drain, not a vent, since it is being used by fixtures above it. Now, is it better than what you have now? Yes, but an inspector would not pass it. They 'got away' with it before since that vertical drain pipe was fairly large, and it would be unlikely that it would get full enough to siphon traps dry downstream. Unlikely doesn't cut it with the codes...they are written for those 'what-if' situations like you're dumping the tub, the dishwasher, all sinks, and toilets at the same time, and the pipe IS full, or very close to it.

To pass (unless the inspector was being very lenient and invokes the grandfather clause), the vents from the stuff you show would have to join that pipe above the stuff above it where that pipe then is functionally only a vent.

 

[Jm66208]

Yes, If you can't get to the house trap vent, then you would need to tie into the vent at 42" above the first floor or 6" above the highest fixture serviced by that drain (typically the lav). Your drawing shows a San-tee on it's back for the standpipe drain. Use a wye & vent off the trap arm.

 

[atomicdog]

REALLY? I would have to tie in to the vent 6" above the sink on the floor above? Wow, this is insane. That vent runs up the wall between brick on one side and Quikrete-style concrete on the other side with a skim coat of plaster over it. I thought if I did what I have pictured here in the drawing it would be okay, but if this isn't even going pass code I may have to just put it all back the wrong way (like it was) and forget about it lol.

The washer must be vented between the p-trap with standpipe and the waste stack
Terry Love

 

[Jadnashua]

As I said, a pipe isn't a vent once it is being used as a drain and vice-versa. So, tying a vent line to a drain like you show would be better than what you have since there'd be a path for air to move better when the WM is draining, but it does not pass today's code. Generally, when you make repairs, the part you replace must then conform to current codes. Sometimes, they're a bit flexible, sometimes they're not. As noted, the fitting you show off the trap arm is not the correct one for that application.

 

[Reach4]

Just an idea....

 

[atomicdog]

Just an idea....

That's genius. That would solve everything actually. Why didn't I think of that?!?!!

 

[atomicdog]

See below...

 

[atomicdog]

Just an idea....
View attachment 22869

I've been putting together my list of items to purchase from Home Depot to do this and I just thought of something that has be a little concerned... I wonder if the bathroom above is even properly vented? I'm suspecting it isn't. Like I wonder if the sink above just ties in to the vent/drain below instead of venting properly using a revent... if that's the case would tying the drain in all the way down at the basement floor be a problem? That would move it's venting 8' lower...

 

[Jadnashua]

The vent is up, not down, so no. Now, for this to work, and keep the status quo of the stuff above, there cannot be anything that drains into the existing line after you move things to a new drop. The rule still applies...once you make a pipe a drain, it cannot become a vent and vice-versa. If the fixtures above are vented into the existing pipe, they should continue to work as they do now with the proposed change.

 

[atomicdog]

That makes sense. Thanks for that clarification.

So based on what I've interpreted from all of the suggestions in this thread... this is what I've come up with. Is this is a winner?