Two Bathroom Piping Advice

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georgesaa

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Hi ,
Just want to stat by saying that I have been using this forum quite a bit over the last few weeks to plan out my plumbing. Thankful for all the advice I see posted on here. I'm in the process of re-doing two washrooms and have come up with the following arrangement, this is to accomodate floor joist locations so I don't need to drill 4in holes for the drains. Would greatly appreciate any advice !
 

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wwhitney

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You drawing is a little unclear because of the crossing of the vertical line labeled "main vent," but I take it that line connects to the lower (on the page) shower trap arm and rises vertically from there.

Assuming that's correct, right now the other shower is wet vented via the combined drain carrying 4 lavs and 2 WCs. You'd need to check Ontario's plumbing code and its wet venting rules to see if that's allowed. An alternative would be to join the other shower trap arm to a drain carry fewer fixtures for wet venting. E.g. the upper (on the page) WC/double lav drain, or the lower (on the page) shower trap arm, after the main vent comes off but before the 4 lavs and 2 WCs join.

Cheers, Wayne
 

georgesaa

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Hi Wayne,
Thank you for the feedback. Hopefully this sketch is a bit more clear, but I can add a dedicated vent line to the second shower , have enough room for that.

I think IPC states that horizontal vent lines must be 6in above fixture flood height, so I can angle that up or put a 90 on it. Joist are 2x 10 so should have enough room to make that happen.
 

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wwhitney

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I think IPC states that horizontal vent lines must be 6in above fixture flood height,
Right, so your latest rendering violates that rule on the new dry vent. The new white vertical labeled vent is fine, but you have a horizontal dry vent below the floor connecting that vertical vent to the left hand shower drain.

If you instead just routed the left hand shower drain along that same horizontal path and connected it to the right hand shower drain between the blue vent and black stack, then the right hand shower drain would be wet venting the left hand shower drain.

And again, that may not be necessary, depending on how much the Ontario Plumbing Code allows on a single wet vent. If a single wet vent is allowed to carry 2 WCs and 4 lavs and be 3" in diameter, then your original drawing is fine.

The above assumes that the shower trap arms in all cases meet the length and fall limits imposed by your plumbing code. That would definitely be a maximum fall of 2" for a 2" trap, and a maximum length of no more than 8', given that the fall must be 1/4" per foot. But your code might impose a length limit that is smaller than 8'.

Cheers, Wayne
 

georgesaa

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Got it, that makes sense. Thanks for the help, I think this is what you where describing.
 

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wwhitney

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Got it, that makes sense. Thanks for the help, I think this is what you where describing.
Almost. I specified that the left shower should join between the blue vent and the black stack. So the blue vent is between the showers, not after the shower drains join each other.

Cheers, Wayne
 

georgesaa

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That works, thanks for the clarification ! Appreciate your help. Took me a while to figure out how these can be routed given the existing floor joist and not having to cut any major holes in them. Had a plumber describe his thoughts on how it should be routed, but I'm much more visual and need to see it drawn out.

A small follow-up question. He mentioned that toilets should always be 'back-washed' from a sink in order to help waste get pushed down. The logic makes sense, once a washroom is used, you go and wash your hands and that water helps push things along. However, I can't find any code reference to it, perhaps the 'back-washing' isn't the proper term.

Also, the connection at the toilet, I've heard you shouldn't use the wye-90 (picture attached) from a vertical to horizontal transition. Can I however you the wye-45 for this (also attached).
 

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wwhitney

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1) On the 'backwashing', not a requirement, but would be a side effect of wet venting a WC via a lav.

2) On the fittings, the one on the left is a sanitary tee, and has nothing to do with a wye. The 'wye' analog would be a combo, a combination wye and 1/8 bend (45), which has the same "tee" pattern, but the side entry ends up much farther from the outlet.

For drainage, if both of the inlets of a "tee" fitting are drains, and the outlet is horizontal, the fitting needs to be a combo. If the outlet is vertical, it can be a sanitary or a combo; with the proviso that if the top entry is wet venting a fixture (edit: other than a toilet) coming in the side, it needs to be a sanitary tee.

So on your latest rendering, the left WC would join that lav drain via a horizonal 3x3x2 combo. On the right WC, you could use a 3" upright combo do do what you've drawn. But for wet venting a WC, it's generally it's preferred, if you have space in the joist bay, to use a horizontal 3" wye, with the WC coming in the side branch via a closet bend (which can be a quarter bend).

Cheers, Wayne
 
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georgesaa

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Thanks again Wayne !

See attached, does this makes sense to you ?

Can't quite fit that 3in horizonta 3" wye for the WC coming in. Need to keep any piping crossing the joists less than 2.75in diameter (2x10 Joists , 1/3 rules ~ 9.25*.3 = 2.75")

For both toilets , I have enough room to add a vent that wouldn't be wet. So if that helps, it's feasible as the toilet is an in-wall and has a bump-out (exterior wall). So could make my bump-out few inches bigger and have a vertical vent. Or maybe have both ? Unless that's bad for some reason.
 

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wwhitney

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- FYI, that fitting you call (1) should be thought of as a 3x2x3 san-tee, the ways you can use it are the same as a san-tee. So you can use it for the "main vent" takeoff if your code allows a san-tee on its back for a vent takeoff; if it doesn't, then use a 3" combo.

- As far as adding a dry vent to the left WC, it's not necessary, and as you haven't specified how you would connect it, I think that would give you a horizontal dry vent under the floor, which is not allowed.

- Fitting 9 should be a double fixture fitting (which may be what you picture, I just can't tell).

- On the back to back 90s on the left double lav, can you rotate the short segment 45 degrees (in either of two ways) so you can instead use a 45 and a 90?

- Likewise on the left shower, can you rotate the trap outlet to eliminate a 90?

- On the right hand WC, do you have room in the joist bay for a 3x3x2 wye plus a street 2" 45 whose inlet is parallel to the wye inlet? Or depending on your code, for a single lav wet venting a WC, 1-1/2" might be allowed. That would be another way to join the WC and the lav on the horizontal, while leaving the WC drainage path straight. The lav drain would jog to the left or right of the WC drain.

Cheers, Wayne
 

georgesaa

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- FYI, that fitting you call (1) should be thought of as a 3x2x3 san-tee, the ways you can use it are the same as a san-tee. So you can use it for the "main vent" takeoff if your code allows a san-tee on its back for a vent takeoff; if it doesn't, then use a 3" combo.

- As far as adding a dry vent to the left WC, it's not necessary, and as you haven't specified how you would connect it, I think that would give you a horizontal dry vent under the floor, which is not allowed.

- Fitting 9 should be a double fixture fitting (which may be what you picture, I just can't tell).

- On the back to back 90s on the left double lav, can you rotate the short segment 45 degrees (in either of two ways) so you can instead use a 45 and a 90?

- Likewise on the left shower, can you rotate the trap outlet to eliminate a 90?

- On the right hand WC, do you have room in the joist bay for a 3x3x2 wye plus a street 2" 45 whose inlet is parallel to the wye inlet? Or depending on your code, for a single lav wet venting a WC, 1-1/2" might be allowed. That would be another way to join the WC and the lav on the horizontal, while leaving the WC drainage path straight. The lav drain would jog to the left or right of the WC drain.

Cheers, Wayne
Wayne, I can't thank you enough for the invaluable information.

1. This is described online as a long 90 deg bend. My code doesn't allow horizontal san-tee on drain pipes, but didn't realize this was considered one. Perhaps combo 3" is the better option. (see https://www.grainger.ca/en/product/90-LONG-SWEEP-ELBOW,3-IN-X-2-IN-HUB/p/WWG1WJG9)

2. For the toilet on the left, the vent would have to go slightly horizontal before going up the wall, so perhaps that won't work. For the toilet on the right, I can take a vent straight up without much problems but the vent would have jog horizontally at about 3feet from the ground. So it would be higher than the toilet, but not higher than the sink.

3. Definitely, can use 45 degrees and get rid of the bends for shower and sinks. Can even add one on the 3in toilet drain on the left hand side of the washroom as I've created a box there for the floor joist. I can do a 45 deg, straight section and another 45 degree.

5. I have enough room for a 3x3x2 wye, but unfortunately not enough room to jog the WC drain left or right. That's the edge of the wall so the joist spacing on there is only 4-5in. Can barely squeeze the 3in pipe in alone. To be clear, the area you are referring to is where I have highlighted a green circle, correct ?
 

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wwhitney

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(1) Hmm, in that case I think you are right, a "long sweep 1/4 bend with low heel inlet" would be the same as a combo. I wasn't aware those were made in long sweep, but I see them now in Charlotte's catalog. As long as you confirm it's long sweep, you can use it where you'd use a combo.

(2) Right, horizontal dry vent under the floor means not allowed. No perhaps.

On the right, you could add a WC dry vent if you want, and it can jog horizontally at least 6" above the WC fixture flood rim, the sink doesn't matter. But it would have to come off the WC drain before it joins the lav drain. [Which it could dow

Once the WC drain hits the lav drain, then the lav is wet venting the WC, and an additional dry vent as shown would just be a bonus, and shouldn't go horizontal until at least 6" above both fixtures.

(5) Yes, the green circle. I'm not following, how about a small dimensioned plan view diagram of that joist bay (they run left right, presumably) showing the WC location and the wall with the lav drain. Seems like it should fit.

Cheers, Wayne
 

georgesaa

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When they say that you can't go horizontal until you're past the flood rim of both fixtures, do 45 degrees count as still being vertical ? I only need to move it a few inches to take it up the wall, so it doesn't have to be a horizontal jog, can be 45 degrees.

See attached plan views
 

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wwhitney

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45 degrees off plumb counts at vertical. But a WC is usually 12" off the wall behind it, and the drain is not usually 12" below the floor, so rising at 45 wouldn't work to get in to the wall behind it. You could use a combo to take off a vent in the wall between the bathrooms, but then you'd have to reroute the lav and bath drains, I think. There's nothing wrong with wet venting via the lav.

As to the right hand lav/WC connection, what I was describing I drew below. If the horizontal 3x3x2 wye plus 2" street 45 (parallel inlets) would fit in the joist bay, that may be a better configuration. [Also, you could roll that up 0-45 degrees above horizontal, and then it would be less wide.] Only one US plumbing code requires it (the IRC), so I'm not sure whether your plumbing code requires it, and if it doesn't, whether it's worth doing the jog.

What's holding up the ends of the joists where the 3" line passes through? Or are you going to drill an oversized hole and then use a metal joist reinforcer?

Cheers, Wayne

plan_view_3.png
 

georgesaa

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They are in-wall toilets, so only a small bump-out of 4in from the wall (accomodate exterior wall). That's why I'm thinking the 45deg would work.

The piping lengths weren't drawn out to scale, so messed up my sketch. But I sister some joists and did a box opening. Luckily the cut joist fell onto a concrete foundation so I was able to cut them short without worrying about deflection. Also double-up all the neighboring ones for good measure. And the beams on the right fall onto an I-Beam so that helped as well. Red are 2in pipes so those can be run through without much problem.

What's the advantage of using a jog on that line as opposed to it being right behind it ?
 

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Reach4

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It is possible to use 2 inch copper, which is 2.125 OD, and couple each end with shielded couplers. This may not be practical for you.
 

georgesaa

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It is possible to use 2 inch copper, which is 2.125 OD, and couple each end with shielded couplers. This may not be practical for you.
Appreciate you chiming in. However, I think I'm fine with cutting slightly bigger.

The joist is only spanned about 7 feet, and it's a 2x10., already oversized for that length, and I'm boring holes near the beam support so deflection and moments there are minimal. Did some quick calculations, not a problem from a structural perspective, and deflection in that area well bellow the L/360 code. I feel comfortable deviating slightly from the code, which I hope has built-in margins as well. I could throw in a couple of reinforcement plates as well if I get worried.
 
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