Toilet install pitch

Thecrow

I want to install a standard toilet in my attic. I have 5 3/4 inch rough cut rafters. Will this be enough room to install the 3 inch pipe and flange etc with a sufficient amount of pitch? The run will be about 2 feet until it drops to a 90 to the 4 inch cast iron drain pipe. I may be able to get more space by chisel the lath and plaster but seriously doubt I can get from the ceiling access. Also my main is a soild 4 cast iron pipe. I've used fernco for my washer but do how would I connect this 3 inch at angle to it? thanks in advance

Zman

The short answer is no the pipe will not fit even with street 90 and a minimal flange. https://assets.speakcdn.com/assets/1824/dwvtech.pdf

As far as the cast iron goes. What else is tied into the 4" pipe on the floor below? How is the floor below vented? How do you intend to vent this new toilet?

To do what you are attempting, someone will need to crack the existing pipe and tie in new fittings. Cracking a pipe in place like that takes some special tools and special know-how.

EBEBRATT-Ed

Why not fir the bathroom floor up? 2" would probably do it.

JUGHNE

This is why you often see WC elevated up 2" or so....raising the "throne" to a higher level.
As far as proper DWV that is another item.

Thecrow

Yeah I can easily cut the perimeter of the new 3/4 plywood floor fir it 2 or 3 inch I guess. I have a clamp thingy where I carefully drilled into the cast main and installed this clamp for my front load washer. It has worked flawlessly. I was hoping they made a similar one with an angle for the drain... The vent stack goes through the roof and it's about 3 inches wide. I either want to tie into it or just run a new one up through I have roofing experience. Or, studor vent or...? Didn't get that far planning yet. I have a beautiful chase behind the shower it's 12 inches deep I plan on running all pipes and water lines and even a 1 inch steam pipe for upstairs rads as well. It comes out about a foot away from the main cast. It also comes next to the hot water heater where I'll run two lines 1/2 right near the heater itself. I have great water pressure so I probably won't be doing 3/4 for water lines in pex.

KC_Jones

I’m going to suggest something else from a perspective you didn’t ask about. How long of a span are those 5 3/4” joists? I hope extremely short because that isn’t very much structure. My attic is framed similarly and for the span they run, and to support actual load they really need to be 2x10’s, which some are now sistered with.

I would suggest you might want to sister all those joists to get the structure correct and it has the added benefit of giving you the room you need for the toilet drain.

Just my $0.02

JUGHNE

Yes, you could sister those 2x6's with 2x10's upwards.
Sitting the 2x10's on the ceilings below. Of course you would have to raise the entire bathroom this much.
I recall a job where the entire attic floor was raised with 2x10's that spanned from bearing wall to bearing wall. Without that it would have been a very springing floor affecting the plaster ceiling below.
'

ChrisJ

My attic has full dimension 2x6s over a 16' span. Approx 16" OC. They're actually 6" not 5 3/4.

They work to hold the ceiling up and minor storage but that's all. They really weren't intended to be walked on much.

I can't remember for sure but I think a 2x6 is good for maybe 8'?

acwagner

It all depends on the expected live and dead loads and the span.

Thecrow

I moved all the insulation and determined that the rafters are 2x6 Rough cut lumber. They are 2 inches wide. They look like a Douglas fir. Everyone of these are 16 OC and the span is 32 by about 15 foot. I have two load bearing walls underneath that are very sturdy. The LBW is in the center of the span. When you walk upstairs absolutely noting makes a noise and is solid as can be. There was old tongue and groove ply 3/4 already down but was in bad shape as far as aesthetics. I installed new sanded 3/4 plywood over entire attic floor. The rough cut with the load bearing wall and in the basement I have proper lallys, its not going anywhere. The bathroom measures now about 12x9. I will cut the plywood out from wall to wall. Ill sister each with a 2x8 or 2x 10. Ill reinstall the floor and make provisions for a small threshold where this bathroom meets the other rooms. If I didnt have that load bearing wall I probably still wouldn't worry with these beams, the entire house was built 1952 (when they used rough cut lumber around here) and even my walls (load bearing walls included) have true 2x4's that are huge. Once I get my extra 2 inches, does anyone have a plan on how to install the toilet flange? Build box slope drain 1/4? Anything else I should be concerned about with my vent stack? Not sure if I can just add everything to my current or just install a new one. It wont be pretty from the outside far as aesthetics however.

Jamie Hall

A VERY rough rule of thumb (and no better than most rules of thumb) for residential construction with "normal" loads and "reasonable" spans is that nominal lumber (modern dimensions, structural grade pine or fir) should be 1 inch in depth for every foot of span, 16 inches on centre. Note the assorted caveats there... Reasonable in terms of span is up to about 16 feet -- if you can get 2 x 16s. The problem isn't so much load capacity -- @ChrisJ 's attic will probably take a surprising load -- but bending. For long spans I like the plywood composite I-beams (plywood web, douglas fir flanges, glued) engineered for the span.

EBEBRATT-Ed

@Thecrow if you look at a dwv 90 it's not 90 degrees it's made to automatically pitch the pipe 1/4"/foot.

Put a square on one and have a look

Thecrow

@EBEBRATT-Ed so if I use this and have fired the floor 2 inches it should be the correctt pitch? I should have 8 inches to work with after the floor is raised. This makes me wonder if I even need to raise the floor. If you look at this picture, the toilet will be installed against this opening so why would I need raise the entire floor if I can build something behind the knee wall?

ChrisJ

Thecrow said:

@EBEBRATT-Ed so if I use this and have fired the floor 2 inches it should be the correctt pitch? I should have 8 inches to work with after the floor is raised. This makes me wonder if I even need to raise the floor. If you look at this picture, the toilet will be installed against this opening so why would I need raise the entire floor if I can build something behind the knee wall?

I have not seen a single picture on the entire thread?

The amount of height you need depends on how far you're going. If you're going 8 feet you need 2 inches of pitch for a 3" pipe typically. If you're going 1 foot you only need a 1/4".

Venting etc is all very important as well.

Thecrow

@ChrisJ, excuse the mess

ChrisJ

Thecrow said:

@ChrisJ, excuse the mess

You want to put the toilet in that hole?

How about that junction box?

Thecrow

@ChrisJ the toilet will be about 4 feet from that hole. The pipes I was hoping to run them to through that hole add a 90 and straight down through the floor is my basement and the main drain is a couple of feet away. The junction box can easily be moved but won't be necessary.

Zman

Would a wall mount toilet make all this easier?

Thecrow

Never heard of one. The area behind the knee wall is not heated. Will it freeze? Can I build a enclosure for the back of it to insulate it? I would not need to rip up the entire floor any help with this idea is much appreciated

Intplm.

@Zman has a good idea. You can actually have a floor mounted toilet that has the drainage discharge out the back but can still sit on the floor. The water supply can come out of the wall or the floor too. Here is a picture of one .

delta T

I am going to guess that the stack you are talking about is a dry vent stack. If you add waste to it, you are creating a waste stack. While you can wet vent fixtures, you cannot do it between floors. By adding the toilet, you are now wet venting the lower fixtures between floors which is a no no.

Zman

@delta T I thought that was the case. Nice job putting it to words!

delta T

@ Zman, haha I'm boning up for my plumbing master's license right now, so I'm really up on the waste and vent stuff at the moment

EdTheHeaterMan

What is the firing rate? And are you using a standard vent? or PVC for a condensing toilet? Are you using Gravity Flow? or a Taco Pump? I'm assuming it is Gas Fired.

This is a Heating help site? Right?

ChrisJ

EdTheHeaterMan said:

What is the firing rate? And are you using a standard vent? or PVC for a condensing toilet? Are you using Gravity Flow? or a Taco Pump? I'm assuming it is Gas Fired.

This is a Heating help site? Right?

You do realize you're responding to a post in the plumbing section. Right?