# Can you really breathe through a submerged toilet?

In the movie kingsmen, (spoiler alert) a room is flooded with water. To stay alive, most of the characters stuff tubing into the available toilets and breathe through that. (you can see them in the picture below in the background)

I wonder if that's actually possible. Luckily, there was an immediate explanation given by another character afterwards for people like me:

For those of you who are still confused, if you can get a breathing tube through the U-bend of a toilet, you have an unlimited air supply. Simple physics... worth remembering.

Except that this explanation didn't make much sense to me. Is this a case of simple physics or rather Hollywood physics? If the room is full of water, each toilet will act as a drain. The trap (which I guess "U-bend" in the quote refers to) will not act as some kind of barrier. The water going down the drain will displace the air in the plumbing. Making it impossible to breathe through the toilet.

I'm not exactly into fluid dynamics, but even if there was some air left in the plumbing , wouldn't it be extremely difficult to suck it out, because of the stream of water that surrounds it due to the Venturi effect?

• I'm with you on this one. I call shenanigans. Where is this supposed unlimited air supply coming from? Further along the plumbing? – Jim Aug 23 '16 at 12:18
• I think it assumes that once you put a tube down far enough, the water level in the pipe would not be up to the top, thus leaving a gap for air? – Noah P Aug 23 '16 at 12:34
• – Noah P Aug 23 '16 at 12:35

For a complete answer, see this identical question on movies stack exchange. However, the brief answer is: P-Traps and vent pipes.

If the water from the room were to make the toilet act as a drain, there would still be air from the vent pipe coming from above, as the water would flow downwards. It would be a nightmare trying to get the tube into the correct position, but possible.

• I guess it's the vent pipe being the answer then, not the P-trap. The vent is the air supply, with or without the trap. The trap alone does not supply any air or produce any air pocket under the circumstances of massive water flow. Given that there's no vent above the toilets, the fact that all surrounding walls are further away than the length of the inserted tubes and that I don't think it's possible at all to get the tube up the vent pipe reliably (and 6 characters that try it easily do it in the movie) I call this Hollywood physics. – null Aug 23 '16 at 12:52
• @null The point being, it is still possible, regardless of difficulty - and yes, I suppose it is the vent pipe, and I'll edit to show that – Noah P Aug 23 '16 at 12:58
• It may not be possible depending how flooding occurred. It could be that the vent pipe itself is completely flooded – Jim Aug 23 '16 at 13:22
• @Jim Yes, in which case it's not possible – Noah P Aug 23 '16 at 13:30
• @MikeDunlavey Yes, I thought my answer made that clear? – Noah P Aug 23 '16 at 13:31

As depicted in the movie it's possible but complicated. The drains serving the toilets would have to be blocked and the vents serving those drains also blocked and pressurized to maintain the water level on the outlet side of the trap.

If the pipes/tubes are long enough, wide enough, and you can suck hard enough, it should work. So whether it works depends on a number of factors.

The water in the room fills the toilet and pushes water down the wastepipe. If there is too much water flowing through the drain completely replacing the air in the drain, then there is little chance.