Sealing toilet on concrete floor

[Maddog]

Have had a chronic problem in our garage with keeping a toilet sealed on the concrete floor. 
It's a PITA!
I get tired of pulling that toilet and reseating it because it's leaking  at the base.  
I've installed a new toilet to replace the original but have had the same issue. 

Granted I'm not a professional plumber but I've installed a few toilets and never had this issue although  never on cement.
Anyone have any ideas on this?
I always use at least two wax rings.
We live in the pacific NW and it's never extreme cold although my wife speculates it might be temperature related and it certainly could be although it's really below 40 in there.
Thanks!

[Snipe Hunter]

The toilet should seal to the flange, not to the floor. There's a flange, right? If the flange is too low or too high you'll have to adjust for it as it won't seal right. Use flange spacers if it's too low. Maybe build up the floor with tile if the flange is too high. Being on a garage floor, I assume you can't move the flange?

And... what's a toilet doing in the garage?

[jteneyck]

If the toilet sits on a toilet flange it shouldn't matter what the floor is made of.  The toilet seals to the flange, independent of the floor.  Of course, the seal has to deal with any height difference between the flange and floor and maybe that's the problem with changing temperatures.  Instead of a wax seal you might consider using a synthetic elastomeric seal.  It should better handle any expansion/contraction issues between the toilet flange and floor. 

John

[Snipe Hunter]

If the toilet sits on a toilet flange it shouldn't matter what the floor is made of.  The toilet seals to the flange, independent of the floor.  Of course, the seal has to deal with any height difference between the flange and floor and maybe that's the problem with changing temperatures.  Instead of a wax seal you might consider using a synthetic elastomeric seal.  It should better handle any expansion/contraction issues between the toilet flange and floor. 

John

Good thinking!

[rlnguy]

I had a similar problem when I moved into a new house, built on a slab.
Within a couple of months the toilet started leaking. I called the builder, they sent a plumber.
He tried to blame it on how I transfer to the toilet from wheelchair.
I told him I grew up in a basement, and the toilet never leaked, so I insisted he look closer at the cause.
He determined the flange was higher than the floor. Not by much, but higher-and that allowed the toilet to "rock" a little, until the seal failed.
He shimmed the edges of the toilet to support it all the way around, and it never leaked, in the 10 years I lived there.
I read, later, that a toilet installed on a concrete floor, should be bedded in plaster around the edges, to support it, so it can't shift or rock.
That's my experience, anyway.
Good luck

[blackhat]

Hate to break this to you guys but the toilet doesn’t have to seal to the flange. The toilet outlet has to be sealed to the waste pipe. The flange is there to make alignment easier and to secure the toilet so the sealing medium isn’t disturbed. A plastic flange that isn’t fastened to the floor will only do one half of its job. An elastomeric seal instead of wax is a good choice but the flange needs to be properly fastened at the correct height. If the toilet will not sit solidly without rocking, it will break the seal and leak. Shims can be your friend there.

[Maddog]

Thanks so much everyone for the very helpful input!
I love woodnet!
Not using the toilet until I resolve this and in the next week or two I'm going to pull it again and really take a careful look at the flange height. 
Someone asked why a toilet in the garage and it's just so convenient to have when working outside getting dirty and muddy etc and not having to take off wet or dirty clothes to go inside. 
Anyway... Thanks again. 
I may be back with more questions after pulling the toilet

[arthropod98]

definitely agree with the shims.  you can get plastic ones for turlets  --  we have 'em in the basement on the tiled floor, which is anything but flat.  shims keep it sturdy and no leaks . . . <knock on wood>.  

[Cooler]

I also used a waxless toilet ring.  Not messy at all.  You can stack them if required.  Seals well.  And you can seat/reseat if required.

I did use plastic shims under the porcelain to level the toilet.  I used the spackers that I used for the tile work.  I forget the brand name, but it is available at both Lowes and Home Depot.  I saw it used on an episode of Ask This Old House.