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Will adding a repair flange and shims allow me to install a level toilet on my slightly off-plumb drain pipe in my basement bathroom with polished concrete floors?

Asked by Önal Orbay
4 weeks ago
Last Updated: October 25, 2024

I’ve been thinking about my basement bathroom project and noticed that the toilet drain installed by the builder is slightly off plumb. I’m wondering how much of a hassle it will be when I need to put the flange on and make sure the toilet is level. My floors are polished concrete, so there’s no room for error with tile.
After getting some advice from this post, I’ve learned that the slight angle shouldn’t be a major issue. Using a flange with a rubber connection inside the 3″ pipe should help make up for any difference and allow the flange to sit flat on the concrete floor (or I can use shims if needed). I now understand that the drain pipe not being level could be the reason for the slight tilt in the toilet drain. Despite some unhelpful responses, I managed to gather enough helpful advice to get the job done.

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Aubree Jean-Baptiste

You’re good. No need to worry.

Aubree Jean-Baptiste

I work as a plumber

Veljko Tišma

If you had looked closely, you would have noticed that he’s inspecting the cut, not the side of the pipe 🤦🏼‍♂️

فاطمه پارسا

Noticed that the pipe coming out of the concrete is not straight. It’s pretty clear just by taking a quick look.

Aubree Jean-Baptiste

Hey man….when we install pipe underground, we make sure to grade it properly. Attach a 90-degree elbow, and you’ll have the same angle of grade vertically. It will work just fine. But thanks for pointing out the obvious

Aubree Jean-Baptiste

And it shouldn’t be when there is a grade on the horizontal piping beneath the concrete

Aubree Jean-Baptiste

Just a quick tip: make sure to tap on the flange down onto the concrete

پرهام نجاتی

Was talking about tap-cons! Pretty much correct!!!!

Clara Lévesque

Even auto-corrected

پرهام نجاتی

Also got me!

Aubree Jean-Baptiste

Is right, haha. Gotta love those tap cons.

Aubree Jean-Baptiste

I’ll make some edits. I always seem to hit the wrong keys, haha

Esma Avan

From a perspective, the floor and flange should have a 1/4” rise over a 2” maximum or a 1/4” rise over 1’ of stub out.

Tim Faure

I think you’ll need a step ladder to reach that toilet.

Irina Sakić

Or…

Leunis Van Liempt

Wow, , that throne is something else! 😂 😂

Tim Faure

‘s faith in humanity has been restored

Mackenzie Green

This photo was taken in the master bathroom of a mansion built in 1876 located across the street from me. The house is approximately 4000 square feet in size. I could only find this particular photo online.

Grayson Anderson

I can’t even imagine a situation where someone would defecate so high up.

Vivan Hughes

To ensure an easy installation of the new toilet, use the black rubber waxless seal designed for 3” or 4” pipes. It features a sticky seal that adheres to the toilet base and fits securely inside the floor drain with 3 rubber ribs. It costs around $8 and offers a quick and worry-free solution.

Bror Risberg

You shouldn’t rely solely on that. Leave some room for adjustments even after gluing it in place. Once you remove the pipe, use a level on the floor flange.

Esma Avan

I also recommend using the side of the pipe to check the level. The cuts may not always be perfectly straight

Harald Stange

The level seems to be in the wrong position for an accurate judgment – is the pipe not perfectly vertical or is it an uneven cut?

Even if the pipe is slightly off vertical, I believe you could simply cut it to be level before attaching the flange and be done with it. That slight deviation from vertical shouldn’t impact the flushing of normal toilet waste.

Vesna Friesen

There won’t be any problems as long as you are familiar with all the products that are available to you. You’ll be okay

Wilhelm Niedermeier

It’s simply PVC, not sturdy steel. You’ll be fine

Emre Özgörkey

Maybe it’s just a slightly crooked cut. Use a square to confirm or trim it and double-check your cut

Sindre Rashid

Check for level using the pipe’s side and add shims to level the floor before installing the toilet… or simply shim the toilet.

Mackenzie Green

Let me explain this to you… make sure it’s level.

Franz Drechsler

Can you think of a more challenging solution to address a non-existent issue?

Sara Onushko

Is a brilliant mind

Owen Garza

Install a fresh layer of concrete on top of the current one at a right angle to the pipe.

Franz Drechsler

Really got it 😂😂😂

Jezdimir Malešević

Laughing

Sedef Korol

That’s the approach I would take as well

Laura Amador

It seems like you’ve been binge-watching the classic Batman TV series. 😉😂😂

Thea Kristensen

‘s best bet is to replace all the hidden drain lines, install new drains, and pour a fresh foundation. 😂😂

Janik Greijdanus

No problem, it’s all good.

Ulrich Dumont

‘t worry, if needed, just cut the pipe flush with the slab and use a repair flange. It needs to extend 4 inches and has fins. But more importantly, is the center of the pipe at least 12 inches away from the finished wall?

Mackenzie Green

I see your point. It seems to be 14 inches long.

فاطمه پارسا

There isn’t a finished wall yet. The green tape on the floor marks the 12” distance to the center of the pipe, showing where the finished wall will be. I suspect the plumbers made a mistake in locating the other pipe (sink drain) as it shouldn’t be inside that wall. It’s not a major issue since I plan to install a vanity, but it would be problematic if I wanted a pedestal sink.

Mackenzie Green

Are you framing the wall with 2x6s?

فاطمه پارسا

Is okay but it’s not a big deal because the sink drain is positioned further into the room than the 12” mark, so increasing the wall depth won’t fix the issue.

Mackenzie Green

I’m a bit puzzled as to why the sink drain has to be 12″ away from the wall. Can you explain the reasoning behind this?

Mackenzie Green

Wow, where are you located with those unusual plumbing codes? Sink drains can definitely go in walls or under cabinets. Just use 2×4 studs and you should be good to go.

فاطمه پارسا

Hey, so the center of the toilet drain should be 12” from the wall, marked by the green tape. The sink drain should fall inside the room, not the wall. Unfortunately, I can’t move the wall further into the room to accommodate the sink drain without violating the 12” rule.

فاطمه پارسا

Hey , just to clarify, it’s not a code problem. I just need a vanity to conceal the drain pipe, can’t have it in the wall.

Mackenzie Green

Hey , remember to run 2×4 studs as I mentioned before. A pedestal could be a good option for you. You’ll need to run a p trap regardless.

Mackenzie Green

Hey , if you ever need toilet clearance, you can find offset flanges and 10″ rough in toilets.

Emilie Sørensen

First off, place it alongside the pipe to mark the pipe instead of the cut. Also, don’t worry, PVC joints can handle uneven angles and still hold up well if they’re not under pressure.

Jezdimir Malešević

Place a laser on the ground to measure the 3 1/4” mark on the pipe, then do some calculations to determine the height for the finished floor, and finally, cut the pipe evenly

فاطمه پارسا

This is the completed polished concrete floor.

Balveer Gatty

I think everything should be sloped, but make sure to cut it level when installing.

Mackenzie Green

Shhh 🤫🤫

Likhitha Banerjee

‘t stress about this too much…

Margot Franck

Correct me if I’m mistaken, but shouldn’t the bottom of the toilet flange be flush with the floor? It might be necessary to excavate around the pipe to ensure the flange sits correctly and isn’t too elevated.

Russell Phillips

Doesn’t glue the flange onto the pipe, instead, you simply cut it flush at the floor and then glue the flange down into the pipe. Typically, standard flanges are glued into pipes that are at least 4 inches or larger in diameter.

Margot Franck

My mine is all finished – living in a mobile home means I have 3 inch pipes. So I just need a standard flange that fits over the smaller pipe.

Mikael Kinnunen

Specializes in mobile home construction, which requires a unique category for inspections that utilize a different type of report form.

Margot Franck

Yeah, they may be cheaply made but still livable. I chose a Palm Harbor thinking they were the best, but when I started remodeling the bathroom, it felt like they hired monkeys from the circus to do the job.

Mikael Kinnunen

I check out a bunch of places – some are even nicer than my own home, haha!

Margot Franck

Hey Sarah! So, I ran into a bit of a situation with a leak in my daughter’s bedroom where the wall meets the roof. The gypsum ceiling covering was so soft that my hand actually went through it. I ended up cutting out a 2-foot section of the ceiling to take a closer look. Turns out, the plywood on the roof is nailed to the ceiling trusses and overhangs about 3 inches past them, causing some bending. The trusses are supposed to be flush with the walls, but they’re about 1 inch above the top plate of the 2×4 walls on one side of the trailer. The roof has a valley running the whole length of the trailer, but thankfully, there hasn’t been any movement in the walls. I’m pretty frustrated about the whole thing, especially since it’s just in time for the rainy season. I’ve covered it all with 3 feet of 10 mil black plastic sheeting tucked under the shingles, and

Mikael Kinnunen

Oh my goodness, that is awful! If you haven’t had the roof done yet, definitely reach out to the place where you purchased it.

Laura Amador

Your first issue is that there isn’t enough space for the flange to slide over the pipe to be glued into place and sit flush with the floor. Could you clear out the concrete around the pipe, leaving about 1/2 inch of space all around and going about 3 inches deep? It would be even better to go the full depth of the slab, and I’m willing to bet you would then have enough space to straighten out the pipe. While there is a retrofit flange available that slides inside the pipe, it does limit your flow, which is something you’ll want to avoid with a toilet.

Lana Caron

Is this a joke?

Elijah Lopez

Haha, maybe the cut was a bit crooked. Try using the level the other way around, genius.

Marie Aubert

You won’t need to cut anything. Just make sure it’s flush with the floor.

Cesar Pascual

Do you know where the vents are for those 2 fixtures?

فاطمه پارسا

Mentioned that it’s positioned roughly 10 feet away at the height of the ceiling. They plan to install a sewage pump as well.

Ray Craig

You shouldn’t run into any issues since you’ll be cutting at a low level.

Benji Kuilder

When tiling the floor, make sure to cut it flush with the tile and use an inside flange. It’s not a huge issue if it’s not perfectly level, it won’t make a difference in the end.

Olava Tøndel

No problem, don’t worry about it.

Jim Simpson

Is this for real?

Mariana Arellano

I thought he was kidding when I read that, . It must be a joke.

Dominic Wilson

It all depends on how the line is running underground. Remember, things tend to flow downhill, so if you want it to go left, you might have to break up that concrete floor.

Auguste Brun

Not a big deal in this situation, but you could always check the level of the pipe.

Swarna Moolya

No need to stress, that’s just a level of knowledge you might not have right now!

Kevin Fox

You know, asking a plumber is a great idea for these types of questions.

Mikael Kinnunen

The edge will be trimmed flush once it’s installed.

Melike Erbay

That will be flush once it’s installed

Runar Brynjulfsen

Seems like the pipe is straight, but the house itself is on a slant. Might be best to rebuild from scratch instead of dealing with the flange installation.

Martha Obrien

‘t worry, consider a mechanical toilet flange. You’ll need to remove part of the floor to allow the flange to fit over the pipe, then secure the flange to be level, accounting for any slight differences.

Eemil Aho

Just sit back and let them complete the work. This task seems to be a bit beyond your expertise.

فاطمه پارسا

Well, since I’ve had 3 leaks already from the work done by these so-called ‘licensed’ plumbers, I think I’ll risk it.

Ramona Taylor

Just a heads up, the drain needs to be sloped for proper drainage. So, any pipe sticking up won’t be level. If it’s level, it won’t drain properly. The pipe will be cut and the flange will be installed level.

فاطمه پارسا

Yes, I understand. The pipe won’t be perfectly vertical after cutting, but it will match the floor level.

Ramona Taylor

Yeah, that way it will be even once it’s cut and the flange is put in place

فاطمه پارسا

I was worried that if I insert the bottom of the flange into the pipe, it might affect the levelness of the top of the flange on the floor. It’s all about geometry. I’ll opt for a repair flange with more flexibility.

Heidi Peters

With a 1/4” slope per foot at a 90-degree angle, you might end up with a wonky pipe sticking out of the floor. The only reason it caught your eye is because it’s so pronounced. But it’s not a major issue.

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