So what’s an s-trap and why are they prohibited
in most states or countries? To understand this, we first need to understand
what a trap’s role is in a plumbing system, and as always if you learn something from
this video, hit the like button to not get punished by the plumbing gods. So what is a trap? A trap, whether it’s an s-trap or a p-trap,
is meant to keep the sewer gases and other dangerous fumes of the city’s sewage system
from coming into your house while allowing waste materials to pass through. Each home produces waste and this waste contains
gases known as methane and ammonia which are both toxic to the human body. Not only are these gases toxic, but they are
also flammable, which means that if they were allowed into your house, they could cause
some major havoc. Some cities had their sewer covers blown off
hundreds of feet into the air as rodents would chew on electrical wires and ignite these
flammable gases, so just imagine what it could do in your home. Every trap has a few different components,
this is the sink or lavatory’s “TAILPIECE”, this is the actual “TRAP” which traps
the sewers gases and this is the “TRAP ARM” that connects to the drain and vent. So now that we know what is what, what these
traps serve and how they actually work, what’s the difference between an s-trap and a p-trap? Simply said, a p-trap is a vented s-trap. Back in ancient civilization, a Greek philosopher
called Pythagoras invented a special glass of wine, called the “Greedy Glass” that
would empty itself on the person drinking when greed would take over. The only reason why this trick glass would
work, is because there’s was no vent, if there was a small opening here, the pressure
would equalize and the siphon wouldn’t occur. Another perfect example is with a straw. We’ve all done this little trick before
where we put a straw in a glass, block off the top and lift it up, the water in the straw
doesn’t come out until the pressure inside of it has been equalized. So as we could see, the greedy cup and the
s-trap you find under your sink are very similar and they both act in the same way, when the
water goes down the vertical pipe, the velocity of it sucks just enough water outta the trap
for the sewer gases to seep through and come into the house. So how do you resolve this problem, well,
you vent it. A ptrap is a bit different, simply for the
fact that the horizontal trap arm doesn’t completely fill up with water and it also
has a dedicated vent to help regulate any positive or negative pressure, if you’d
be able to see behind your walls, you’d have a vent pipe like this that would eventually
go out the roof to provide fresh air to the system. This vent, similar to the one I made before
on the trick glass, is what equalizes the pressure in the system to prevent any siphoning. This siphoning can come from an improperly
vented toilet nearby for example, as toilets displace a lot of air in the pipes, if you
had an s-trap, it would most probably siphon out the water and use the actual drain as
a vent. Now if you have s-traps on all of your fixtures
in your home and you aren’t having any problems, you don’t really need to address these,
but what if you always smell sewer gases, how do you go about fixing it? There’s 3 possible ways, a typical ptrap
vent, the AAV, the Loop Vent or the Combo vent. So first off, is the p-trap I mentioned before
and I already explained how it works but the only thing is that during a renovation for
example, these vents aren’t always accessible and breaking all the walls is not really an
option, which leads me to option number 2. The AAV. The AAV (Air Admittance Valve), which is also
known as a studor vent or sure vent, is by far the easiest way of modifying an s-trap. The only problem with them is that, to be
code, they need to be installed 6” above the flood level of the fixture for them to
be considered a proper vent and most people don’t follow this rule, so they don’t
pass inspection and some cities prohibit them because of this. They sell dedicated boxes like this to install
them in so that you don’t just have an AAV on your wall looking weird. Also, since it’s a mechanical device, there’s
chances of it breaking in the open position which would let sewer gases in. However, some municipalities allow them, which
is why it’s important to inform yourself before planning anything. The third way is to make what we call a loop
vent. A loop vent is basically a normal vent but
rerouted to fit the needs. It requires more plumbing yes, but this way,
there’s no mechanical devices that could fail, which makes it a much safer option for
venting. The only con is that you do need to have access
to a nearby vent pipe to connect to, which once again may require some demolition, but
as always, getting the proper permits for this is mandatory, and what I am saying is
for informing purposes only and can vary from state to state. And that pretty much covers it for s-traps. If you guys have any questions about this
topic, just drop me a comment below and I’ll do my best to answer you, like, share and
subscribe if you learned something and until the next one, thanks for watching!
