Drain/Vent layout Question

[john330]

I am adding an upstairs bathroom and have some questions about how I can vent the system.

The flow of the drainage is sink->shower->toilet. The sink drains into 1.5" pipe which then changes into a 2" pipe before the shower trap. The shower drains into the 2" pipe which then changes to a 3" pipe before the toilet drains into the 3". The drain then continues to flow down to the crawlspace and then on to the septic tank.

My questions are 1) Will this drain layout work? and 2) How can I vent the shower and toilet together? (The sink will be vented by itself to the attic and tied into the shower/toilet vent before exiting the roof).

Please note - in all pictures, the sink and it's drain are not shown, but are upstream of the shower.

Can I vent the shower/toilet after the toilet as in "Figure 1"
or
Should I vent the shower and wet vent the toilet to the shower vent as in "Figure 2"?
or
Should I vent the toilet and tie in the sink/shower drain downstream of the toilet vent as in Figure 3?

 

[SewerRatz]

Why don't you combine figure 2 and three? If you have room to put a vent by the shower and room to put it by the water closet all is good. You can tie the vent near the shower into the vent on the other side of the water closet inches above the drain.

 

[Sponsor]

 

[john330]

Why don't you combine figure 2 and three? If you have room to put a vent by the shower and room to put it by the water closet all is good. You can tie the vent near the shower into the vent on the other side of the water closet inches above the drain.

Thanks SewerRatz.....venting both is an option, I was just seeing if there was an easier/simpler way.

You mention combining figures 2 and 3, but can I combine 1 and 2 instead? Is there any reason why the sink/shower drain can't be upstream of the toilet or does it need to tie in to the 3" pipe downstream of the toilet?

Thanks again!

 

[SewerRatz]

Yep can combine 1 and 2 just fine. After I posted I thought about what I said and was thinking have the shower at the end will help wash down the line better.

 

[Jar546]

Personally I would just do #2 but increase the vent to 2-1/2" since you will be pulling at least 5 dfu's. Save yourself work, pipe and expense with the same result.

 

[Jar546]

I would set up the shower with a 2" pipe and trap size then at the beginning of the 3" horizontal line Tee up to your 2-1/2" vent for the water closet.

Your 2" trap for the shower can be 8' away from the vent at a 1/4" per ft slope but it sounds like this will be relatively close so vent to trap distance does not sound like an issue for you.

Is there a bathroom sink?

Good luck.

 

[john330]

I would set up the shower with a 2" pipe and trap size then at the beginning of the 3" horizontal line Tee up to your 2-1/2" vent for the water closet.

Your 2" trap for the shower can be 8' away from the vent at a 1/4" per ft slope but it sounds like this will be relatively close so vent to trap distance does not sound like an issue for you.

Is there a bathroom sink?

Good luck.

There is a sink on the other side of the bathroom that will be vented by itself and tie into the shower/toilet vent in the attic before exiting the roof. Below is an overhead picture of the layout.

The black is the drain and the red dots are where I can vent up. I can't vent through the "Back Wall" without add'l framing because it partially sits on a floor joist.

Thanks for the advice........

 

[PJPlumber]

What you see in the image is exactly what I am proposing:

Hey guys, I have a quick question based upon drawing #2 (but without the sink that is mentioned in the posts): I am reversing the location of a shower and toilet that are 8 ft apart from each other and were on separate lines. This leaves me with a 3" toilet drain running all of the way to my new shower and also happens to have a 2" dedicated vent. The reason I have this is because this is where the toilet was but now the shower will be there instead. Also, this 3" inch line is running right under where the new toilet wants to be. It would be very convenient if I could simply add the new toilet into the existing 3" drain line just like it is shown in image #2. So, my question is this: Can I have my shower and toilet on the same 3" drain line, 8 ft apart from each other with only the 2" vent line that is very close to the shower drain as long as there is a proper 1/4" per ft drop? Its a guest bath so the toilet and shower would never be used at the same time (if that matters).

By the way: The toilet would now be just 24 inches away from where the line goes vertical and down to the main line and out to street. Please let me know what you think and thanks in advance for weighing in. Happy Thanksgiving!

 

[Terry]

The toilet would now be just 24 inches away from where the line goes vertical and down to the main line and out to street. Please let me know what you think and thanks in advance for weighing in. Happy Thanksgiving!

A santee on it's back doesn't guide waster down the line. It hits the bottom of the pipe and goes both directions. That's why a wye fitting is needed in a position like that.
A better solution would be to come down with a 90 from the toilet, and further down the line on the horizontal, add a 2" wye that extends to the existing 2" vent, which will vent both the shower and the toilet. The fitting for the vent is wye+45 or combo fitting since it would be on it's back.

 

[PJPlumber]

A santee on it's back doesn't guide waster down the line. It hits the bottom of the pipe and goes both directions. That's why a wye fitting is needed in a position like that.
A better solution would be to come down with a 90 from the toilet, and further down the line on the horizontal, add a 2" wye that extends to the existing 2" vent, which will vent both the shower and the toilet. The fitting for the vent is wye+45 or combo fitting since it would be on it's back.

Terry, many thanks for getting back with me. My drawing was admittedly an over simplification. The toilet would actually be offset from the 3" pipe by approx. a foot or so horizontally. This would allow me to "sweep" the waste into the 3" pipe with a proper connection and have the 2" shower line come in from the left and a little above so that toilet waste would be less likely to run back toward the shower. I could make it so that the 2" vent line enters the 3" line from closer to the middle, maybe 3 feet from the shower and 5 feet from the toilet (?)... or would it be okay to leave the 2" vent closer to the shower where it is presently located? This would save me a bunch of work. Thanks again for your advice.

It could be more like this...

 

[JoeNW]

View attachment 37029

What you see in the image is exactly what I am proposing:

Hey guys, I have a quick question based upon drawing #2 (but without the sink that is mentioned in the posts): I am reversing the location of a shower and toilet that are 8 ft apart from each other and were on separate lines. This leaves me with a 3" toilet drain running all of the way to my new shower and also happens to have a 2" dedicated vent. The reason I have this is because this is where the toilet was but now the shower will be there instead. Also, this 3" inch line is running right under where the new toilet wants to be. It would be very convenient if I could simply add the new toilet into the existing 3" drain line just like it is shown in image #2. So, my question is this: Can I have my shower and toilet on the same 3" drain line, 8 ft apart from each other with only the 2" vent line that is very close to the shower drain as long as there is a proper 1/4" per ft drop? Its a guest bath so the toilet and shower would never be used at the same time (if that matters).

By the way: The toilet would now be just 24 inches away from where the line goes vertical and down to the main line and out to street. Please let me know what you think and thanks in advance for weighing in. Happy Thanksgiving!

View attachment 37029

What you see in the image is exactly what I am proposing:

Hey guys, I have a quick question based upon drawing #2 (but without the sink that is mentioned in the posts): I am reversing the location of a shower and toilet that are 8 ft apart from each other and were on separate lines. This leaves me with a 3" toilet drain running all of the way to my new shower and also happens to have a 2" dedicated vent. The reason I have this is because this is where the toilet was but now the shower will be there instead. Also, this 3" inch line is running right under where the new toilet wants to be. It would be very convenient if I could simply add the new toilet into the existing 3" drain line just like it is shown in image #2. So, my question is this: Can I have my shower and toilet on the same 3" drain line, 8 ft apart from each other with only the 2" vent line that is very close to the shower drain as long as there is a proper 1/4" per ft drop? Its a guest bath so the toilet and shower would never be used at the same time (if that matters).

By the way: The toilet would now be just 24 inches away from where the line goes vertical and down to the main line and out to street. Please let me know what you think and thanks in advance for weighing in. Happy Thanksgiving!

This diagram touches on something I’m trying to resolve, and you mentioned that this is an oversimplification, but as shown - can you still wet vent this toilet as it drops vertically into the horizontal pipe? I may be misreading, but does UPC 908.2 prevent a vertical fixture drain dropping into a horizontal drain?

UPC 908.2. (IRC 3108.1) “Fixture drains to horizontal wet vent must connect horizontally & independently, vertical connections require a dry vent”