How to Repipe

[wwhitney]

I think I want to implement solution #1 for the shower and tub. I’m not able to visualize how to pipe things based off what you said, in that scenario. Could you make a rough drawing, or help me another way?

Attached in a rough sketch; the top is a floor plan, and the bottom is an elevation to clarify one option for the WC connections. Pipes in the plane of the drawing are shown as lines, while pipes perpendicular to the plane of the drawing (i.e. vertical for a floor plan) are shown as circles.

On the shower and tub, option #1 involved a soffit in the adjoining room so that they can be wet vented by the horizontal 3" line in the existing soffit. That makes the geometry simplest, it's all in one plane. I'm showing each trap as a circle and a short segment which is the footprint of the U-bend; you can probably rotate the u-bend around the inlet, along with the elbow, as required at each fixture to get the necessary horizontal separation between the tub and shower drains. [If not, to get more separation you can point the shower trap outlet at a 22.5 or 45 degree angle to the joists, then use a 22.5 or 45 degree elbow to bring it parallel to the joists.] The particular trap configurations I show are just examples, use whatever works for the geometry.

On the WCs, as discussed earlier, there is some debate about what the proper orientation of the wyes should be for the WC to be wet vented. I've shown the simplest option, which has the wyes fully upright, as it is easiest to draw and to execute. But if you are concerned that may not be proper, you can roll those wyes 45 degrees or 90 degrees and use a few more elbows to make the connection. In that scenario, I think you'd find it easier to move the entire 3" horizontal soffit drain closer or farther from the wall, so that it does not run directly under the near WC. That would make the near WC connection simpler.

For the tub and shower drains, and for the 2 WCs, I show closely spaced wyes, because in each case you have two drains coming in from the same joist bay. The tightest pattern there would be to use a street wye for the upstream drain, directly into a wye or combo for the downstream drain. So I suggest getting that fitting configuration worked out first, which will then tell you the spacing you need between the two drains as they approach the horizontal 3" soffit drain.

Cheers, Wayne

 

[NeedPlumbingHelp]

Attached in a rough sketch; the top is a floor plan, and the bottom is an elevation to clarify one option for the WC connections. Pipes in the plane of the drawing are shown as lines, while pipes perpendicular to the plane of the drawing (i.e. vertical for a floor plan) are shown as circles.

On the shower and tub, option #1 involved a soffit in the adjoining room so that they can be wet vented by the horizontal 3" line in the existing soffit. That makes the geometry simplest, it's all in one plane. I'm showing each trap as a circle and a short segment which is the footprint of the U-bend; you can probably rotate the u-bend around the inlet, along with the elbow, as required at each fixture to get the necessary horizontal separation between the tub and shower drains. [If not, to get more separation you can point the shower trap outlet at a 22.5 or 45 degree angle to the joists, then use a 22.5 or 45 degree elbow to bring it parallel to the joists.] The particular trap configurations I show are just examples, use whatever works for the geometry.

On the WCs, as discussed earlier, there is some debate about what the proper orientation of the wyes should be for the WC to be wet vented. I've shown the simplest option, which has the wyes fully upright, as it is easiest to draw and to execute. But if you are concerned that may not be proper, you can roll those wyes 45 degrees or 90 degrees and use a few more elbows to make the connection. In that scenario, I think you'd find it easier to move the entire 3" horizontal soffit drain closer or farther from the wall, so that it does not run directly under the near WC. That would make the near WC connection simpler.

For the tub and shower drains, and for the 2 WCs, I show closely spaced wyes, because in each case you have two drains coming in from the same joist bay. The tightest pattern there would be to use a street wye for the upstream drain, directly into a wye or combo for the downstream drain. So I suggest getting that fitting configuration worked out first, which will then tell you the spacing you need between the two drains as they approach the horizontal 3" soffit drain.

Cheers, Wayne

View attachment 75484

Thanks.

1. Did someone mention earlier in the thread that the shower drains were too high to be wet vented by the horizontal drain? Does putting the p-traps in assist in that situation?

2. If I am planning on renovating both bathrooms within the next few years, is it a bad idea to redo the piping for the shower and tub, at this moment? The reason I’m asking is because I am wondering if new shower and bath fixtures would have cutouts for their drains in different areas, possibly, even if it is only like an inch?

Thanks for all the help, so far.

 

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[wwhitney]

1) That comment referred to the existing situation with the drains and traps up in the joists. And that's why solution #1 requires an additional soffit for the shower and tub p-traps and trap arms, to allow those to be below the joists, for the horizontal wet venting.

2) I don't think that's a reason to defer fixing your s-traps on the tub and shower. If when you redo the bathrooms the drain locations move (which is more likely than not), you'd just have to open up your new soffit and adjust the plumbing. [Or open up the subfloor above and redo it from above.]

Cheers, Wayne

 

[NeedPlumbingHelp]

1) That comment referred to the existing situation with the drains and traps up in the joists. And that's why solution #1 requires an additional soffit for the shower and tub p-traps and trap arms, to allow those to be below the joists, for the horizontal wet venting.

2) I don't think that's a reason to defer fixing your s-traps on the tub and shower. If when you redo the bathrooms the drain locations move (which is more likely than not), you'd just have to open up your new soffit and adjust the plumbing. [Or open up the subfloor above and redo it from above.]

Cheers, Wayne

Great. Thanks.

Do you have a picture of an optimal drop from a bathtub or shower drain? How long should the drop be before the p-trap is attached? How far above will the lines that come back from the shower and bathtub be above the horizontal run?

 

[wwhitney]

The trap arm needs to be sloped at least 1/4" per foot, and the total fall from the trap outlet to the 3" horizontal soffit drain can be no more than the pipe internal diameter (so 2" for a 2" drain).

I'm pretty sure I've said the above earlier in this thread, so you may benefit from going back to the beginning and reviewing the whole thread.

Cheers, Wayne

 

[NeedPlumbingHelp]

The trap arm needs to be sloped at least 1/4" per foot, and the total fall from the trap outlet to the 3" horizontal soffit drain can be no more than the pipe internal diameter (so 2" for a 2" drain).

I'm pretty sure I've said the above earlier in this thread, so you may benefit from going back to the beginning and reviewing the whole thread.

Cheers, Wayne

Thanks

I’m going to read through it all, again.

I’m trying to learn as much as I can. Is the sole reason I am replacing the shower and tub drain so that the traps don’t have their liquid siphoned from them, and gas enters the living space? I haven’t had any issues with the tub or shower draining.

 

[wwhitney]

Is the sole reason I am replacing the shower and tub drain so that the traps don’t have their liquid siphoned from them, and gas enters the living space?

Yes, S traps are wrong for the reasons you stated, so they need to be replaced with properly vented P traps.

Cheers, Wayne

 

[Terry]

Thanks

I’m going to read through it all, again.

I’m trying to learn as much as I can. Is the sole reason I am replacing the shower and tub drain so that the traps don’t have their liquid siphoned from them, and gas enters the living space? I haven’t had any issues with the tub or shower draining.

It's to prevent your home from smelling, and in some cases toxic depending on what you have nearby.
You want pipes to drain, but not to siphon the water seal.

For instance, I was at a friends home, helping her in the kitchen, preparing dinner. I was standing near the kitchen sink, and noticed that instead of a wonderful smell of cooking, it smelled horrible. I open the cabinet doors to the sink, and saw that they had left off the p-trap to the sink. No seal whatsoever.
The next day I opened the wall up, dropped the santee in the wall, there was a vent there. Added the p-trap and that cured the smells in her kitchen.

In new construction, they don't let the new guys touch waste and vents for about a year. They have them running water where they can't mess things up too much. Water can go up and down and around.
Waste runs down hill, and venting takes place to prevent traps from siphoning. For every pipe going down, there is a pipe going up through the roof.

 

[NeedPlumbingHelp]

It's to prevent your home from smelling, and in some cases toxic depending on what you have nearby.
You want pipes to drain, but not to siphon the water seal.

For instance, I was at a friends home, helping her in the kitchen, preparing dinner. I was standing near the kitchen sink, and noticed that instead of a wonderful smell of cooking, it smelled horrible. I open the cabinet doors to the sink, and saw that they had left off the p-trap to the sink. No seal whatsoever.
The next day I opened the wall up, dropped the santee in the wall, there was a vent there. Added the p-trap and that cured the smells in her kitchen.

In new construction, they don't let the new guys touch waste and vents for about a year. They have them running water where they can't mess things up too much. Water can go up and down and around.
Waste runs down hill, and venting takes place to prevent traps from siphoning. For every pipe going down, there is a pipe going up through the roof.

Thanks to both of you.

If it doesn’t smell in the bathrooms, does that mean there is no issue, or that it possibly is a very small amount? I guess I wonder what the danger level is,
kind of like different levels of radon.

Methane is odorless, though. So there’s that.

I am planning on repiping the shower and bathtub, regardless.

wwhitney… why are there 2 different schools of thought on horizontal wet venting? Is it not something that can be tested in a lab, or has been tested in the past? How will I know which route to take with the wyes on my horizontal run up to the WCs? It would seem that the scenario with the wyes pointing upward would certainly be easier.

 

[NeedPlumbingHelp]

Also, how can I replace the overflow pipe on the bathtub? Is that something I can access from below?

 

[wwhitney]

wwhitney… why are there 2 different schools of thought on horizontal wet venting?

The disagreement is just in relation to WCs. Showers and tubs have to obey the "trap weir" rule, that the trap arm falls no more than one internal pipe diameter before being vented (this avoids the risk of siphoning). So their trap arms having to come into the wet vent on the horizontal.

WCs don't have that limitation, as they have an integral trap that is designed to siphon, and therefore their fixture drains have no limitation on fall before being vented. So that would permit the arrangement suggested with the upright wyes for the WC connections to the horizontal wet vent.

The argument against this arrangement, as far as I can tell, is (a) it's called horizontal wet venting, so the drains have to join on the horizontal and (b) the big slug of water coming in from a WC could block the whole cross section of the horizontal wet vent and interrupt the venting.

The counterargument would be that (a) above is not spelled out in the plumbing codes; the definition of "horizontal branch drain" includes the possibility of vertical segments, which are present whenever a lav is used for wet venting; and at least in your case, there are no fixtures between the WCs and the (presumably) dry vented lavs, so (b) above is immaterial. I do agree that (b) is something that ought to be testable in a lab.

Also, how can I replace the overflow pipe on the bathtub? Is that something I can access from below?

Why do you want to replace the overflow?

It looks to me that if you cut a big enough access hole in the drywall below and are replacing the bath waste, you could do the replacement from below with a fair amount of running upstairs and down to get the geometry correct while connecting the new overflow shoe to the tub. Access to the non-tub side of the overflow would make it easier.

Cheers, Wayne

 

[NeedPlumbingHelp]

The disagreement is just in relation to WCs. Showers and tubs have to obey the "trap weir" rule, that the trap arm falls no more than one internal pipe diameter before being vented (this avoids the risk of siphoning). So their trap arms having to come into the wet vent on the horizontal.

WCs don't have that limitation, as they have an integral trap that is designed to siphon, and therefore their fixture drains have no limitation on fall before being vented. So that would permit the arrangement suggested with the upright wyes for the WC connections to the horizontal wet vent.

The argument against this arrangement, as far as I can tell, is (a) it's called horizontal wet venting, so the drains have to join on the horizontal and (b) the big slug of water coming in from a WC could block the whole cross section of the horizontal wet vent and interrupt the venting.

The counterargument would be that (a) above is not spelled out in the plumbing codes; the definition of "horizontal branch drain" includes the possibility of vertical segments, which are present whenever a lav is used for wet venting; and at least in your case, there are no fixtures between the WCs and the (presumably) dry vented lavs, so (b) above is immaterial. I do agree that (b) is something that ought to be testable in a lab.


Why do you want to replace the overflow?

It looks to me that if you cut a big enough access hole in the drywall below and are replacing the bath waste, you could do the replacement from below with a fair amount of running upstairs and down to get the geometry correct while connecting the new overflow shoe to the tub. Access to the non-tub side of the overflow would make it easier.

Cheers, Wayne

Thanks a lot.

I thought I needed to replace that brass looking portion under the tub, because someone was saying one nut was significantly corroded and the other was missing. I thought maybe I was supposed to replace all that, along with the dwv underneath?

 

[wwhitney]

Yes, if it's corroded you should replace it, and use non-slip joint fittings. If it's in good condition, you can leave the brass components as they are if you provide an access panel for the slip joint connections (not sure if the latter is a code requirement or just a good idea). The lowest brass piece I think is a fine threaded tail piece that would unscrew from the brass tee; if so you could replace it with a longer one for your lowered trap.

Cheers, Wayne