Need help w/ new bathroom plumbing

[jeff_bathroom]

Hi,
I've spoken w/ Lazypup about this and will post a photo.
I wanted to attach a photo showing the drain and vent for new toilet, but I see it's too large. I'll take another later in low res and send it. It's a little different because I could not vent behind the toilet due to the electrical panel behind the toilet in the wall. So, I brought the drain forward at
a 45 degree angle about 2 feet, and vented up and off to the right in the wall adjacent to the toilet. I know you can vent a 3" drain within six feet or so. The vent is about 2 feet down and over from the toilet flange. The pipes in the soon to be attached photo are not glued; they're just taped into place for now. So, I can make adjustments if anyone thinks this is not a configuration that would pass inspection. Thanks for your help !

Jeff

[jeff_bathroom]

Photos

Attached are two photos. One of the drain/vent that I spoke of above.
The other is showing the other end of the new 3" drain where it will have
to connect to existing 3" pipe going the length of the house.

[LazyPup]

After review both your photo's and floor plan that you emailed to me I worked out the required DWV(drain, waste & vent requirements for your project.

The shower requires a 2" trap and drain line which can be connected directly to the 3" branch drain by means of a 3x3x2 Wye. Since the total overall length of the waste arm from the trap weir to the vented 3" line is less than 8' you will not be required any additional vent.

At the junction where the 3" branch turns 90deg towards the water closet you will need to install a Wye & 1/8 bend or combo with a cleanout on the end of the Wye.

At the lavatory riser you will need a 3x3x1-1/2" Wye & 1/8 bend or combo, then run a 1-1/2" riser up to the sinks. At the point where the sinks connect to the riser you must install a "double sanitary TEE" (commonly called a sanitary cross) with a 1-1/2" waste arm to each sink trap. Continue the 1-1/2" riser up through the roof for a vent. This is the only vent you will be required to install.

[jeff_bathroom]

Thanks Lazypup.
However I don't want to cut another hole in the roof. I would rather
use the existing vent even though that may be more work. I don't feel comfortable as a DIY'er getting involved with the roof.
I also don't know what you mean by "riser". What I understand a riser to
be is the supply to the fixture.
In addition, I had decided for the shower to use an existing 2" drain and vent that had previously been used for the original utility sink. Sorry; that change is not shown in my plans.
What I'm looking for rather than a modification to my plan (at the moment) is to know if what I have currently in place in the first photo is viable. Is there anything wrong with running the drain for the toilet at a 45 degree angle off of the toilet flange, and venting the way the photo shows?
Anyway, you mentioned that I'm making this too difficult. Problem is that I've already done some of that work. There are holes already made, etc. I can proceed with some of this if I can know whether the DWV for the toilet shown in the first photo is within code. Thanks for your help !

[LazyPup]

To answer your first question, "what is a riser?", in Plumbing vernacular a line in the vertical plane is called a "Riser" while a line in the horizontal plane is called a "Run".

The concept of venting is without a doubt the most difficult aspect of plumbing to understand. While it is true that all fixtures must have a vent, not all vents must run vertically through the roof, in fact we strive to minimize the number of actual roof penetrations and in some instances with careful layout and planning an entire house can be plumbed with only one or perhaps two vents through the roof.

In order to better understand vent placement we must first understand the distinction between a "Vented Branch Line" and a "Waste Arm".

By necessity there must always be a short section of horizontal pipe from the vent to the trap which is called the "Waste Arm or Trap Arm". The waste arm and trap are on the upstream flow side of the vent and therefore it must serve as both the drain and vent for that section of pipe.

The minimum permitted length of a waste arm is two 2x the pipe diameter measured from the "Trap Weir" (The weir is the point where water actually spills out of the trap).

Under the IRC the maximum permitted length is the pipe diameter divided by the required pitch. I.E. an 1-1/2 line requires a pitch of 1/4" per foot so the maximum length of an 1-1/2" waste arm is 1.5 / .25 = 6ft. (A trap arm serving only a watercloset is unlimited.)

The UPC uses basically the same formula, then they derate the length by approximately 40% so the maximum length is determined by a table in the code.
1-1/4" =2'6"
1-1/2" =3'6"
2" = 5'
3" =6'
4" or larger = 10'

A horizontal pipe on the downstream side of a vent is called a "Vented Branch" and may run any required distance.

SEE ATTACHED ILLUSTRATION:

In the case of your bathroom the 2" line from the shower is well under the permissible length for a 2" waste arm so no additional venting is required on the shower.

You will see in my previous illustration that the 1-1/2" vertical riser from the 3" horizontal drain up to the lavatory and utility sink connection is extending upward to create a vent at that point.

In this configuration the horizontal waste arms from the vertical pipe to both the lavatory and utility sink traps should be well within the maximum allowable lengths for waste arms.

Given that this vent is also venting the horizontal 3" under the floor, all the remaining 3" downstream of that connection point would be classified as a vented branch and not restricted in length. In turn the 3" line on the upstream side of that connection to the watercloset is well within the maximum 6' permitted by the UPC and since that section of line serves no fixtures other than the watercloset the IRC has no length limitation thus there is not additional venting required at the watercloset.

Understanding your reluctance to create any additional penetrations through the roof, there are other options for terminating the vent. Both the IRC and UPC will permit a flat horizontal vent run after the vent is 6" above the flood level rim of the highest fixture served by that vent. In this case a simple solution would be to run the vent vertically into the attic space, then turn horizontal and run it to the main vent which is shown to the left side of the shower in your floor plan. The horizontal vent section must be pitched at 1/4" per foot dropping down from the main vent to the auxillary vent at the lavatory.

Although I am not a great proponent of doing so, the IRC will permit auxillary vents to be simply terminated as an open pipe in the attic space.

[jeff_bathroom]

Thanks Lazypup for the extended explanation. I will be running the vents
into the attic, then horizontally connecting to the existing vent thru the roof.
You mentioned the pitch being 1/4" per foot. Can the pitch
be greater than that briefly as in the case of my photo? I still need to know if the drain/vent configuration for the toilet in the attached photo is ok. Can I slope 45 degrees immediately off of the toilet flange for a couple feet before venting upward as depicted?

[jeff_bathroom]

If I need to come off the toilet flange at 90 degrees like a standard
closet flange, how long can the vertical part be before the 90 degree turn?
The joists are 8 1/2" deep. I would like to not have to cut into them. Shouldn't I be able to go below them over toward the vent in the photo.
That way I can get rid of the 45 degree section that seems to be an issue.

[LazyPup]

The vent that you are currently connecting at the watercloset cannot provide the necessary venting for the lavatory and utililtiy sink, however once you have the sinks vented correctly the vent you have at the watercloset would be redundant and totally unneccessary. Since you have not yet glued the pipes in place my recommendation would be to simply abandon that vent altogether.

To answer your question about vent pitch. We may only create a horizontal vent after the vent reaches a vertical elevation of 6" above the flood level rim of the highest fixture served by that vent, which in this case would be 6" above the rim of the watercloset bowl.
Below that elevation a vent must run vertical or may offset providing the maximum angle is not greater than 45 degrees from vertical.

[jeff_bathroom]

Thanks Lazypup,
I understand that the horizontally running vent must be 6" above highest fixture overflow. What I'm asking is whether the closet bend or 90 degree turn coming down from the toilet flange can make the 90 degree turn about 9" below the subfloor? Is it ok to make that turn 9" or more below the flange so that I don't have to cut thru the joists when the drain starts going horizontally?
The other issue with venting the lavatory or utility sink and using that vent
as the water closet vent (if that's what you're suggesting) is that the vent pipe must be 2". I think we can agree on that; that the vent for the 3" toilet pipe must be 2", correct ?
Problem is that the wall behind the lavatory and toilet is 2x4 plate and is a load-bearing wall. According to what I'm reading, I cannot put a 2" vent requiring about a 2 7/8" hole thru a 2x4 in a load bearing wall. However the wall that I chose to vent the toilet thru is not load-bearing, so that's where I'm currently set up to vent the toilet.
Or, if I entirely misunderstood how you want to vent the toilet, please let me know. If you had wanted me to vent the toilet via the 2" shower vent, I might understand that, but wouldn't quite know how that is to connect.
Remember that the shower will use the existing 2" drain and vent in place from the original utility sink. Even if I were to want to do that, at this point it might be more work for me given that I've already cut the hole for the 2" vent next to the water closet. The pipes are in place all the way into the attic. It's really just a matter of now to connect the closet bend to that vent and get rid of that 45 degree angle pipe that you see in the picture. Hence my first question above; from the subfloor/toilet flange, can I run the 3" toilet drain pipe down more than 9" before making the 90 degree turn to get beneath the joists. I plan on running the 3" toilet drain horizontally directly underneath that 2" vent that I created in the non-load-bearing wall and connect with a combo.

[LazyPup]

The additional vertical drop under the closet flange is no problem providing the angle section is no flatter than 45 degrees from vertical.

There is no need to have a 2" vent.

Under the INTERNATIONAL RESIDENTIAL CODE all structures are required to have one "Main Vent" which must run undiminished in size from the building main drain up and out through the roof. All other vents are classified as "Auxillary Vents" and may be reduced to 1/2 the diamter of the line they serve but in no case may they be smaller than 1-1/4". Since you are venting a 3" line you only need 3" / 2 = 1-1/2" vent which is exactly what i specified at the lavatory and utility sink location.

The remaining 3" line upstream of the lavatory drain riser to the closet flange is classified as a waste arm for the watercloset, and the IRC permits a watercloset waste arm to run an unlimited distance without additional venting so there is no vent required at the watercloset location where you are attempting to install the 2" vent.

Under the UNIFORM PLUMBING CODE vents may be reduced to 1/2 the diameter of the lines they serve providing the aggregate total cross sectional area of all vents is equal to or greater than the cross sectional area of the building main drain. Understanding that this is to be an additional vent, we can then assume that the pre-existing vents in the structure already meet or exceed the agregate cross sectional area of the building main drain, so here again a 3" / 2 = 1-1/2" therefore the 1-1/2" vent is sufficient to meet the need.

However you work it out you will be required to have the 1-1/2" vent at the lavatory & utility sink location as I previously specified, and once that vent is established it will provide all the venting required for the lavatory, utility sink, watercloset & shower, so here again, the 2" you have connected to the watercloset is not necessary.

All remaining 3" line downstream of the sink & lavatory riser is classified as a 'Vented branch drain".

The shower is not required a vent because the waste arm for the shower is less than the maximum length of a 2" waste arm (IRC 8' & UPC 5'), therefore it will be "Wet Venting" directly from the 3" horizontal vented branch drain and no additional venting is required.

The bottom line is, you are required to have the 1-1/2"vent at the sink riser. Once you have that you will not need any other vents.

[jeff_bathroom]

Well, that's interesting news.
Code aside; how about performance though? Would individual / additional
vents make draining better ?

[jeff_bathroom]

Hmmm

I thought I posted a reply but don't see it. So, here goes again with some additional thoughts/questions.

I was wondering about performance if the lavatory, utility sink, shower and water closet are all venting off this 1 1/2 inch vent pipe. Remember that I don't want to run an additional vent thru the roof, so this 1 1/2 inch vent pipe coming from the lavatory will go into the attic and connect to the
2" vent thru the roof. Are all these fixtures going to drain as well as they might w/ additional vents to each fixture ; code aside...?

And, since I had planned to connect the shower to the 2" drain and vent used for the original utility sink, could that vent be used for all instead of running a vent for the lavatory?

[LazyPup]

As I have stated many times in the past,the codes are very specific and there simply is no guess work in designing a DWV (Drain,Waste & Vent) system.

The first step in the process is to consult a table in the code that assigns a DFU(Drainage Fixture Unit) value to each fixture. From the DFU value we then consult another table that lists the pipe sizes and the maximum number of DFU's permitted for each size of pipe.

When a drain line is properly sized a horizontal run of pipe will be 1/2 full under full load. This then leaves the upper half of the pipe open for the tranfer of vent air. If a pipe is too small the liquid passing through the line will fill the line like a piston in a cylander and push the air ahead as it moves. This results in a negative air pressure void in the pipe behind the moving liquid and ultimately results in sucking the water out of the traps. (S-traps have been outlawed for fixture drains because they actually form a natural syphon and result in sucking the water out of the traps.) Once the liquid has passed the trap is then left open and toxic or potentially explosive sewer gasses can then enter the structure.

If a line diameter is too big the level of liquid in the line is not sufficient to suspend any solid waste that may be present in the line, so the solids settle to the bottom of the pipe as the liquid flows around them. Once the liquid passes the solids are left exposed to vent air and then dry in place causing a clog. In fact, an oversized line will actually clog much faster than an undersized line.

Understanding that the upper half of a properly sized drain line is always open to vent air, the code then permit an unvented waste arm to run from the drain to the trap providing the length of the line is short enough to insure there will be an adequate amount of vent air in that section of pipe. This explains the length limits on waste arms. In a nutshell, the bottom of the pipe at the upstream end may be no higher than the top of the pipe at the downstream discharge end, thus we use the formula diameter divided by pitch to determine the maximum length. (The UPC then derates the length by approximately 40%).

A watercloset is the singular exception to the no S-trap rule. The trap, which is built into the bowl base of a watercloset is in fact an S-trap. When the flush begins the water rises rapidly in the bowl, causing it to spill over the trapway in a large slug which forms a natural syphon through the trapway. This explains how a toilet is able to lift the last remaining water out of the base of the bowl up and through the trapway. In order to insure the trapway of a watercloset is not left open the watercloset fill valve has a trap primer line which discharges a small amount of water down the standpipe and into the bowl during the tank fill cycle. While there is nothing in the code prohibiting you from connecting that 2" vent in the manner you have started, in function, having a vent too near a watercloset can tend to break the required syphon action prematurely and result in a watercloset with a sluggish flush. In my opinion your watercloset would probably work much better if you do not connect that additional vent and just use the vent at the sink & lavatory riser.

[jeff_bathroom]

That's very interesting and somehow makes sense.
So, in a nutshell, we want to use a wet vent for the water closet
which in this case is the lavatory 1 1/2" vent, correct ?

[LazyPup]

Technically speaking the section of pipe from the sink and lavatory sanitary cross down to the 3" line , as well as all the 3" pipe downstream from that junction to the point where it meets the house main vent is a wet vent and by extension, the house main drain and house sewer are wet vented all the way to the nearest manhole on the municipal sewer line..