Fitting at soil pipe(with diagrams now)

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Coolwhip, Aug 1, 2020.

  1. Coolwhip

    Coolwhip New Member

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    Nov 9, 2019
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    GA
    Whats the best way to transition from cast iron soil pipe to pvc? 4 in to 3 in.

    Previously there was just a 4 in x 3 in flexible rubber coupling with 2 worm gear clamps on it, connected to a 3 inch L piece of 3 in PVC pipe(you still call this nipple? guess it could be eliminated with a street elbow) going to the elbow leading to the toilet.

    Thats what I was going to do again, before reading about no hub couplings, soil pipe adapter and hub x no hub adapters, and also seeing universal pipe connectors like the SP140.

    The transition will be above ground, but as said in the crawl space, its just like 6 inches of iron soil pipe sticking out of the ground, very shallow crawl space...I'd like to have the elbow coming off the soil pipe as low as possible for more slope flexibility, but its probably not a huge deal to be a bit higher if needed.

    Also, theres a good bit of swollen(but still hard and intact) rust on the soil pipe, do I need to do anything about that? If so, how should I address it?

    ----------------

    Also, planned on putting a 3 x 3 x 2 elbow with low heel inlet on the soil pipe, the 3" inlet would obviously go to toilet, but on the 2" inlet I was going to attach either a 2x2x2x2 double san tee(unless a double fixture tee or double combination tee-wye would be more suitable??) with the right inlet leading to the tub/shower, and the left inlet leading to a branch serving the kitchen., with the straight up inlet leading to a double fixture tee serving a double vanity and AAV.

    Does this sound good? Or would putting an all hub san tee with right and left inlets directly on the soil pipe make more sense? I kind of thought the toilet would be better served with its own elbow and everything else draining into it from above, don't know why just my gut....BUT, it might be necessary to get the kitchen branch sloped down a bit more than what an elbow with low heel inlet would allow....if necessary could I use a san with with left inlet hub, left inlet serving the kitchen but bathroom fixtures still draining in from above...or is there no reason not to use an all hub san tee with both right and left inlets straight on the soil pipe?

    Another also....someone raised the concern to me that the 2" low heel inlet could act as a choke point if all fixtures were draining at once? And to maybe consider a 3" all hub san tee, with 3 x 3 x 2 x 2 double san tee? But my DFUs shouldn't exceed the limit of a 2" pipe, so thats not a problem right?

    Any thoughts on this? I'm a horrible artist but I'll try to draw up a diagram tomorrow morning, thanks.
     
    Last edited: Aug 1, 2020
  2. Jeff H Young

    Jeff H Young In the Trades

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    mission cp43 to a 3 inch pvc spigot 1/4 bend knock off gently loose stuff on outside of 4 inch with wire brush or just kinda scrape it cleaner. i guess its coming straight up out of ground. any way thats my take on it so far
     
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  4. Coolwhip

    Coolwhip New Member

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    Thank you for the reply. Yes it just sticks straight out of the ground. I have wire brushed it, kind of figured that was good enough...should I bother with any kind of rust converter/inhibitor?(I know this is worrying about a very far off problem, but I don't want this thing to be leaking 25 years from now because of it, probably being silly, but this crawlspace is stupid low and I never ever want to get under here again if I don't have to)

    I edited my original post, but I don't guess a street elbow with a low heel inlet would be something easy to find...so I think I am stuck with hub/socket, I assume using an inside connector(or whatever the right term is?) is no problem. I guess using a 3 x 4 no hub coupling and inside connector(really just 3 inches of cut pipe) vs using a 4 x 4 no hub coupling with an adapter is 6 in one and half a dozen in the other?

    One question though...the flexible rubber coupling allow some degree of movement, I assume a no hub coupling will be a bit stiffer....will I need to account for in some way the fact that the toilet drain pipe will be coming in at a slope(1/4" drop/ft)? When hub its pairing with will be horizontal? Sorry if that seems like a ridiculous question, I'm fairly new to this and cautious, don't want to make any mistakes.

    I appreciate everyone being patient, still learning the terminology so bear with me if some things I said don't seem to make sense.
     
    Last edited: Aug 1, 2020
  5. Jeff H Young

    Jeff H Young In the Trades

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    Ok put a 3 inch spigot santee on top of the cast then a 3x3x2x2 double y or combi on top then a piece of 3 inch thru floor with clean out a 3x2 bushing on top then do your lavs and vent 2 inch (or perhaps 3 inch all the way up through roof)
     
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  6. Coolwhip

    Coolwhip New Member

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    So the low heel could act as choke point? This is a real concern? I thought since 2" pipe can handle 21-26 DFU and I'll have less than 15 on it total it'd be fine.

    Do I definitely not want to use an all hub san tee on the cast iron, with everything feeding into that?

    I'm not going to run any vents to the roof, there are obstructions in the way that could make it untenable, the soil pie has a 4" SVP about a foot behind it venting through the roof, I'm just going to use AAVs everywhere else as needed.

    So I'm pretty settled on using a no hub coupling, do I need to have any type of PVC actually go past the rim(inside) of the cast iron, to prevent leaking where the cast iron and coupling meet?

    Is it better for the PVC to match the soil pipes size and then reduce from there? Or just have the no hub coupling do the reducing?

    I guess now. I'm most concerned about what I should do right at the soil pipe, I may need to keep it as low as possible to avoid having to route the kitchen branch to the 3" pipe serving the toilet with a wye...if I get too high off the cast iron I may not being able to have enough slope from the kitchen, which is why I ask about an all hub san tee, or even the tub if I go much higher than what I get with a elbow w/ low heel inlet and double san tee.

    I have a clean out on the soil pipe outside the house...you are saying I need a clean out between the soil pipe and bathroom fixtures? Anywhere else? Is this really necessary? My state uses the IPC.

    Here are some pictures I tried to draw(told you I was no artist). not that its super important for most these questions but the crawl space is MUCH tighter than the drawings make it look and the ground is very uneven, clearance from ground to floor joists rangings from 8"-14"...but the soil pipe is protruding from a low point in the ground, giving it about 18" of clearance to the floor joists.


    [​IMG]
    [​IMG]
     
    Last edited: Aug 2, 2020
  7. Coolwhip

    Coolwhip New Member

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    [​IMG]
    [​IMG]

    Everything will be 2 inch pipe after the traps, with a 2 inch drain and trap on the tub, except for the toilet waste pipe obviously.

    If there is no reason to use an all hub san tee w/ l+r inlets, I guess I'd just do that...my gut just told me it'd be better for the toilet to have its own elbow(with low heel inlet connecting everything else)

    Besides the clean out question, and some more opinions on the best way to connect the soil pipe to the PVC...my two big concerns at this point are.

    Of the three options to connect to the soil pipe, which one should I use? Are there pros and cons to each? Should I definitely not use an all hub san tee w/ l+r?

    and

    If using an elbow with low heel inlet, whats the proper 4 way fittings to connect to it? A double san tee? A double combination wye-tee? Or a double fixture tee?
     
    Last edited: Aug 2, 2020
  8. wwhitney

    wwhitney Active Member

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    Berkeley, CA
    I believe a low heel elbow with inlet is only to be used in the orientation you've shown AND with the inlet as vent. To connect drains as you've shown, you'd simply use a san-tee.

    Above it, you have a choice of double san-tee, double fixture fitting, or double combo. Since the drain lines are already vented, it doesn't matter.

    And if you'd prefer to combine the san-tee and double san-tee into a single fitting (3" san-tee with 2" L and R inlets), that would be fine. I see no advantage to separating the toilet waste from the tub/sinks. How are you venting the toilet(s)?

    As to joining to the buried cast iron, I assume you are going to use a Mission or Fernco coupling as suggested. Those are slightly different from no hub couplings, they have a thicker shield that is uncorrugated. So I would call them shielded rubber couplings to distinguish them from no hubs.

    Cheers, Wayne
     
  9. Reach4

    Reach4 Well-Known Member

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    Can you organize your sketch like the one on page 12 of https://wabo.memberclicks.net/assets/pdfs/Plumbing_Venting_Brochure_2018.pdf ?

    It does not need to be so pictorial, but it should be from the side of the flow, vs head-on. The wet venting is only for the bathroom stuff -- vented lavatory, shower/tub, toilet.

    Join the kitchen waste after all of the bathroom stuff. Use wyes in the horizontal plane to add wet-vented bathroom stuff.
     
  10. Coolwhip

    Coolwhip New Member

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    I didn't realize that, thank you. I presume there is no reason not to let the coupling do the reducing for me. I see a distinction for SV and XHCI, how do I know which one I need? There is an CI elbow with hubs under the dirt, but its just a straight pipe sticking up, I don't know if it was built this way or cut some time ago, the house is over 110+ years old but I don't know how old the soil pipe is.

    There's an SVP that runs through the roof, the soil pipe goes underground, then about 2 feet back an SVP comes up through the roof, thats all the toilet needs right?

    When you say "above it" do you mean between the lavs(I plan on using a double fixture tee there, unless a double combi wye-tee would be better, I know not to use a double san-tee)? Because I thought you were saying I shouldn't drain into a low heel inlet and only use it for a vent?...well its probably moot anyways after this next part.

    So there's no problem with this?

    [​IMG]

    Basically, I wanted to know what the best way to connect all of this to the soil pipe was, with an eye to the fact that the kitchen branch can't come in too high or it won't have enough slope....if there's no problem with the above fitting then that definitely seems the way to go to me. Also, at first I was thinking of putting an AAV after the tub trap, but the AAV between the Lavs should be all that is needed, right?

    [​IMG]

    Jeff mentioned a clean out between the soil pipe and the lavs...since I have a clean out outside the house already is this still necessary?

    I've tried to do better in the above drawings.

    What do you mean join the kitchen stuff after all of the bathroom? The soil pipe is located directly under the bathroom, and the kitchen is located on the opposite side of the house...I could(if I had to) run the kitchen into a wye along the toilet waste pipe, but I can't get it "behind" the drains for the lavs and tub.
     
    Last edited: Aug 3, 2020
  11. Reach4

    Reach4 Well-Known Member

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    By "after", I meant to join kitchen drainage downstream of the bathroom stuff that is involved in wet venting.

    I think now understand what you are trying to do -- bring everything into a 5-port manifold. That is not something I am familiar with.

    You don't want to dig below the current dirt level to bring the kitchen waste in below the other stuff joins, which would be the normal thing, I think. I am not a plumber.
     
  12. wwhitney

    wwhitney Active Member

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    Measure the outer diameter of the pipe you need to connect to, and find the matching Fernco or Mission coupling.

    I don't see any problem with the "triple" san-tee. Presumably the kitchen drain is already vented. The vented lavatory can vertically wet vent the bathtub as long as the trap arm is not too long.

    As to the AAV, I'm not so familiar with them. I briefly looked at the IPC section on them, and it mentioned two different types, I think it was fixture vs stack AAVs. I'm thinking that since you propose to use one AAV for the two lavs, the tub, and the toilet, you'd be using a stack type AAV. And I did see that those have to be six inches above the flood rim level of any fixture it is venting. And accessible for maintenance/replacement.

    I'm not that familiar with cleanout requirements.

    Cheers, Wayne
     
  13. Reach4

    Reach4 Well-Known Member

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    Could you do something like this?
    Toilet joins shower in horizontal plane at 3 inch wye.

    Santee in red, or better double wye if you have room.

    Wye venting shower is in vertical plane. The 90 above that moves the wet vent over to be under the lavatory, which provides the wet venting to shower and toilet.
     

    Attached Files:

  14. wwhitney

    wwhitney Active Member

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    So for an already vented drain pipe transitioning from horizontal to vertical, is a wye better than a san-tee? Both are allowed, unlike vertical to horizontal or horizontal to horizontal, where a wye is required.

    Going upstream, with a 90 after the vertical wye, the vent will end up horizontal, and you'll need a 90 to get back to vertical, not a 45. If, at the first bend after the wye, you want the vent to stay 45 degrees off vertical, but turn a 90 when projected in plan, that takes a 60 degree bend, see below.

    Cheers, Wayne

    Math: Say a pipe is initially parallel to the unit vector (cos 45, 0, sin 45), and you want to turn it to be parallel to the unit vector (0, cos 45, sin 45). Then the angle you need to bend is arcos(dot product) = arccos (0.5) = 60 degrees.
     
  15. Reach4

    Reach4 Well-Known Member

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    You cannot rod out a double santee from either side; snake jumps across. So the top of the santee should be a functional cleanout. With a double wye, you can rod from left or right, and snake goes down.

    Go to the up and to the right 45 degrees in the vertical plane that contains the trap arm. Turn 90 degrees to the left in that same plane, and you are then rising to the left at 45 degrees. Picture was intended to be isometric but has flaws.
     
  16. wwhitney

    wwhitney Active Member

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    Ah, thanks for the explanation.

    I didn't catch that your drawing was all in one plane, the plane defined by the vertical soil pipe and the shower drain. That works if the lavatory drain is also in that plane (or close enough). I can't quite tell from the OP's drawings, it seems like there's some offset but I'm not sure which dimension.

    But is it worth it to jog the lavatory drain away from the soil pipe so it can hit the horizontal drain upstream of the toilet for standard wet venting? Versus just using a stack with the triple san-tee? That's an honest quesiton, I'm not sure of the pros and cons of the two different solutions. As far as a cleanout goes with the triple san-tee, the 3" vertical line could extend up to a 3" cleanout just below the lav double san tee, accessible in one of the lav vanities (assuming there is at least one vanity).

    Cheers, Wayne
     
  17. Reach4

    Reach4 Well-Known Member

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    Wet venting only includes bathroom stuff. The jog was to let the toilet join the lavatory drain before joining the kitchen waste. So if that kitchen stuff was part of the triple, that would seem to mess that up. But I don't know. So the jog was to let the toilet join the lavatory drain before joining the kitchen waste.

    It may be that the lavatory drain is not actually right above the drain pipe into the dirt, so the ugly jog might not be needed.

    You understand that I am trying to consider what would meet code, rather than what would probably work fine even though not meeting code.
     
  18. wwhitney

    wwhitney Active Member

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    With the triple san-tee, the requirement would be that the tub trap arm and the toilet trap arm are under the maximum lengths, then the san-tee would provide the venting. The lavatories are allowed to drain through that as a vertical wet vent. And the air admittance valve (probably required to be 6" above the lavatory flood rim level) would complete the vent.

    So I think that triple san-tee solution is also IPC compliant. I don't see how having the already vented kitchen sink drain coming into the same san-tee interferes with the san-tee's venting of the toilet and bathtub.

    Edit: to the OP, if you have the height available, and the only drain that needs to be low is the kitchen drain because of the length of its run, you could just stack two san-tees, one on top of the other. The lower san-tee would accept the kitchen drain, and the upper san-tee would have a side inlet to accept both the toilet and the bathtub. Those two inlets are at right angles, so perhaps that avoids the rodding difficulty that Reach4 explained.

    Cheers, Wayne
     
    Last edited: Aug 3, 2020
  19. Coolwhip

    Coolwhip New Member

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    Not exactly. the soil pipe is between the lavs, almost directly in front of the right lavatory ....I "could" have the lavs enter the soil pipe from the left(the same side of the kitchen) but it wouldn't be as convenient.

    The toilet has to hit the soil pipe straight on, there are brick peers in the way that would prevent me from aiming to the right like that. I could have the kitchen run into the toilet drain pipe instead of the fitting on the soil pipe...but I'd rather not.

    On top of that, there isn't much room to make L/R shifts while maintaining slope, those shifts would have to be completely horizontal to not run out of space.

    I think(may not have the clearance), with some doing, I could have the lavs join up with the tub drain pipe with a wye, and the toilet join the san-tee on the soil pipe and the kitchen run into a side inlet on the soil pipe....with the lavs+tub running to a second fitting on top of the san-tee sitting on the soil pipe with a clean out on top...but why is this necessary if I have a clean out on the soil pipe outside the home?

    That's why I am using a double fixture tee on the lavs, but I figured if there was a need to snake anything above the soil pipe I could just come in from a different drain. I have a clean out on the exterior of the house about 20 feet away to snake the soil pipe itself.

    I am having trouble understanding exactly what problem you are trying to fix due to my lack of knowledge...can you explain it for me so I can understand how to fix it it better? I appreciate the help very much.

    I can't do it exactly like that, the toilet would need need to be on the lower san tee as well for slope...I could do something like the second option in the second picture I posted, with the toilet+kitchen going in the bottom fitting and tub+lavs going in the top.

    Even then I'm not 100% sure I have the height to stack two san-tees on top of each other before running into the floor joists, but I'll check next time I am there.

    What about using wyes with side inlets?

    Like this with L+R instead of the san-tee.

    or this with L inlet, with a wye or san tee on top for that lav+tub

    Though I'm not sure this solves anything because I am not sure what I am trying to solve...if its just snaking, whats wrong with just snaking the drain the clog exists on for the drain pipes, and snaking the soil pipe form the exterior if needed? Or if I really need a clean out to reach the soil pipe from inside the house, I can put one along the drain heading to the lavs(though I'd rather not, because it will either have to be above the finished floor or in a very hard to get to part of the crawlspace(possibly between floor joists). Or I could put one on the toilet drain pipe. But I am really not understanding why I need a clean out...is it just for code? Or am I not getting why snaking from a different drain or snaking the exterior clean out is not sufficient?

    And whats the problem with using an elbow with a low heel inlet and double fixture tee or double wye-tee on top again?

    It seems like you think the all hub san-tee w/ L+R would probably work, whats the possible issue with it? The kitchen will have its own vent, if that was the problemm if its snaking whats wrong with snaking from the exterior clean out or snaking from a different drain for anything above the soil pipe?
     
    Last edited: Aug 4, 2020
  20. Reach4

    Reach4 Well-Known Member

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    You want to vent the shower and toilet. Is this going to happen in fact with your proposal? Logic says yes. Is this going to be considered proper venting under IPC? I tend to think not, but I am not sure. AFAIK, wet venting is not allowed to mix with kitchen drainage.

    That was the problem I was trying to fix.
     
    Last edited: Aug 4, 2020
  21. wwhitney

    wwhitney Active Member

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    So how far in plan is it from the (a) the toilet flange and (b) the bathtub overflow pipe to the soil pipe? Even better would be coordinates for all three points in plan.

    If you're worried about height, then either of those are taller than a san-tee, so your chances of stacking a san-tee on one of them is less. And for the bathtub, if the fitting is to provide the vent, it has to be a san-tee. [Toilets can use a wye because they have an intentionally siphoning trap that is refilled after each flush, so the usual rules designed to prevent trap siphoning don't apply.]

    That fitting has a similar configuration of openings as a san-tee (top, bottom, side). The elbow with inlet can only be used when the bottom and side are drainage, and the top (heel inlet) is a dry vent. If the top is a drain, then you need a san-tee. [That's the rule as I understand it, although thinking about it now I don't see why.] But what advantage would it have over a san-tee?

    Cheers, Wayne
     
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