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15 April 2007

AskMeCha Science - I have a wall mounted toilet. My SO insist that my weight on it doubles if I stand on it.[More:] ...So, my 50 odd kilo are more than his 100-odd if I stand on the toilet. I'm not grasping this at all. Does this mean that a 120 kilo dude can't use our toilet? background, seems I broke it by standing on it for a wee second, or so he claims.
The only weight not on it when sitting is that of your legs, and only half of the weight of your legs at that. Give or take. Probably not even that much, since most thighs are going to outweigh calves.

Anyway, the problem is weight distribution between sitting and standing. When sitting, the bulk is toward the back while standing places the further forward. In this, the toilet acts as a fulcrum and like any lever, the more distance from the pivot point, the greater the force.

In a sense, you are both wrongs and you are both right.
posted by mischief 15 April | 11:50
Where did the toilet break? Where were you standing on it? It's not just the weight that matters; where the weight was applied is also important.

In other words, if you just sit on it and pick your feet up (so the seat is the only thing supporting you), you're applying the same force to the unit as if you were standing on it. However, 1) the force is distributed over more surface area and 2) the location of the force may be different than if you were standing on the rim or something.

So it's not implausible that you broke it by standing on it, but not by his logic.
posted by muddgirl 15 April | 11:50
I just got up, have barely dragged on some clothes and the coffee is still brewing. Maybe I'll explain all that gibberish I just wrote later.
posted by mischief 15 April | 11:52
I'm not a gravitational physics sciencemagician, but I think your SO is wrong about all that. You can break toilets if you stand on them, for sure, but it isn't because you "double your weight" when you do.
posted by cmonkey 15 April | 12:00
I'm still slogging through my first coffee. Weight is force, and force has a vector component, so yes, you can double your weight or even triple it, depending on an abundance of factors.

Mass however remains constant (well, it remains constant if we ignore using the toilet for its usual purpose).
posted by mischief 15 April | 12:17
To answer muddgirl - the toilet now makes a slightly 'crunchy' squeak when sitting down on it, as if the drywall that covers the steel skeleton and holds the tiles all purdy has broken or ripped somewhere. I stood dead center on the lid of it, with one foot, pulling myself up to reach all that stuff on out of the way shelves when SO marches in and yelps "you'll break the toilet". I've stood on it before, and I'm careful when I do it, but it's only today that it's makeing that little scratchy noise, and only yesterday he caught me on it. He also claims that the toilet is now crooked compared to the tile "lines", but it was always that way because that croked line has been bugging the hell out of me when I take long baths.

pics of toilet & bathroom in general. :)

So yeah, I guess it could be my fault, but I'm pretty wigged out that a loo would be that easy to break.
posted by dabitch 15 April | 12:46
No answers for you, but I love your bathroom!!!
posted by occhiblu 15 April | 13:03
The icon tile ROCKS, dabitch!
posted by BoringPostcards 15 April | 13:56
Assuming a uniformly distributed mass (people are close enough unless they call you 150 FFF) a 50 kg person standing in the centre of the lid is applying alot less force than a 100kg person centred on the ring.
posted by Mitheral 15 April | 13:59
Well, the toilet must be anchored to the studs inside the wall, and not to the drywall or tile. That said, drywall doesn't tend to be very flexible, especially if tiled, and if the toilet's natural flex were increased a bit, you could then make the drywall/tile crack and thus squeak.

Anyway, it sounds to me less like the "toilet" broke, than that something inside the wall got loosened. Unfortunately, if the wall is tiled, it's gonna be expensive to rip that down to get inside the wall to fix the anchoring.

I'm looking at this installation example and comparing it with your "before" picture, assuming those two long shafts are anchors that the plumber already attached to the wall structure. Maybe somebody needs to hold their head down there while someone sits on the commode to see where the sound is really coming from.
posted by stilicho 15 April | 15:06
Thanks occhiblu & BoringPostcards - I'm pretty much in loooove with it. ;)

Good idea stilicho. I'll have to do that!
posted by dabitch 15 April | 15:19
Gym update || Sue Ellen Sells Her Modernist House

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