Hello. A new kitchen sink was just installed in an apartment that our family
owns. I installed drainage pipes to connect the drain on the new sink to the
existing drainage pipe that goes into the wall (then goes outside).
It's the first time I've ever done plumbing so it was a bit of a learning
experience. I noticed after it was done that I could have shortened the
vertical distance of the amount of water in the p-trap by about 2.25". The
vertical distance of the water in the p-trap is 7" when I could have made it
This apartment unit is not rented and is kept vacant so that family members
can stay there when they come to town. My 82 year old mom, who's in good
shape, will stay there overnight about once a week. I mention this to give
an idea how long the water will be staying in the p-trap.
Is a vertical distance of 7" of water in the p-trap too much if the kitchen
sink will only be used about one day a week? Will that much water cause
odors or attract mosquitoes? Should I shorten it to 4.75" to avoid those
possible problems? Finally does anyone know if this is addressed in a
Thanks for any feedback.
I've known traps to stink but attracting mosquitoes seems unlikely to be a
real problem. Any amount of water in the trap would tend to act the same.
(petulance does not prefer deep water nor shallow water)
What you really want to avoid is having too small of a trap such that the
water evaporates before you use it again, at that point sewer gasses can
enter the house and really stink up the kitchen.
Too large of a trap and it may be more prone to clogging with debris or
If you worry about the sanitary nature of the water down there, get in the
habit of running the sink a few minutes and pouring a glass of lysol (or
similar) in the trap before you vacate each week.
The 7" referred to the vertical distance from the lowest point on the
midline of the trap to the midline of the pipe going into the wall. Based on
the very helpful comments I have received on this ng (thanks!), I am going
to remove a small vertical section (see my other post in this thread that I
just sent for all the details) so what was 7" will be about 4.5" when it's
I measured the vertical distance in the bathroom trap and that was about 4"
so I figure 4.5" should work.
Thanks for the feedback.
We've gotten lost in all your details. From what it sounds like, you
should have been able to simply buy a tubular P trap and installed it.
Traps are specifically designed not only to hold a water seal, but to be
self-cleansing. When someone manufactures his own trap, the danger is that
it won't flush the water through.
sorry cant understand you.
bottom line..trap will controll amount of water unless trap is down hill of
the trap (the weir of the trap) has to be above the hole in the wall where
Sorry I wasn't clearer. I just did another post where I tried explaining it
again, hopefully it's more clear on that post.
I probably didn't realize the importance making sure the straight part of
the pipe that connects to the pipe going into the wall has a definite
downward tilt to it so gravity can do its thing. Thanks for emphasizing
Thanks for the feedback.
I probably made it a lot longer than necessary but I wanted to be thorough.
Here's hopefully a better explanation:
A new sink was installed and the drain location on the new sink is different
than the original sink drain location. At the new sink drain, a new straight
drain pipe (pipe 1) will go down from it.
Attached to pipe 1 will be pipe 2, which contains the 180 degree trap
section, so water enters pipe 2 in a down direction and exits pipe 2 in an
Attached to pipe 2 will be pipe 3. The end of pipe 3 to be connected to
pipe 2 has a 90 degree turn. So water enters pipe 3 going in an up
direction, then turns 90 degrees into a horizontal direction (actually
slightly downhill direction), then goes in a straight (horizontal) direction
for about 8" (the length of the straight portion of pipe 3).
The straight end of pipe 3 connects directly into the existing horizontal
pipe going into the wall.
I had had a little 2" section of pipe between pipe 2 and pipe 3 which I will
remove. This will decrease the trap length by 2". I'm defining trap length
as the (vertical) distance from the bottom of the trap (at the centerline)
to where the drain water begins flowing in an almost horizontal direction
(at the centerline of that pipe) - the location on pipe 3 just after the 90
I can't have pipe 2 and pipe 3 be one pipe (meaning a pipe containing both
the 180 degree trap and the 90 degree turn).
Here's why: if I use such a pipe, there's no way to get the drain water
flowing out of pipe 3 to go directly into the existing pipe going into the
wall. I would have to use 45 or 30 degree sections at the end of pipe 3 to
connect the end of pipe 3 to the existing pipe going into the wall.
By rotating pipe 2 (the trap pipe) at the pipe 1 - pipe 2 interface and pipe
3 at the pipe 2 - pipe 3 interface, I can line up pipe 3 so it goes directly
into the existing pipe going into the wall.
Well I don't have a choice in making the p-trap consist of two pipes rather
than one (for the reasons I stated above).
Your last comment has made me realize the importance of making sure the
water is flowing downhill so it can enter the pipe going into the wall.
This means I have to make sure the straight part of pipe 3 (the pipe that
connects to the existing pipe going into the wall) is slightly downhill, not
horizontal. Thanks for emphasizing that.
Thanks for the feedback.
I am sorry I could not make it any more clear than I already have.
You dont want that answer I guess.
You want to go on with your terrible description of your plumbing and
get someone to say you have done the right thing.
It is a very very simple answer. If you can remove a small bit of pipe and
change the amount of water the trap holds then you have certianly botched
the install. There is no way around this , sorry.
If your new sink is much deeper then you might be shit out of luck and need
to replumb the whole drain.
A drum trap will buy you a couple of inches.
just currious but are you a liberal?
I understood you just fine but you apparently didn't understand me. I was
trying to change that but apparently you didn't understant the second
explanation. You never said what it was I wrote that was confusing you.
I understand the drainpipe going into the wall (and the straight portion of
the pipe connected to it) has to have a downward tilt. I am quite aware of
the phenomenon of gravity.
If the words "180 degrees" or "90 degrees" confuses you, consult a
You sound like a paranoid person.
Sorry but that's absurd. The configuration I'm using (with the 2" pipe gone)
is apparently a common configuration since that's how the plumbing is done
under my kitchen sink and under the sink in the bathroom I just checked
(both of which were not done by me - I don't know who did them - but both
have worked just fine for many years).
No need for that - gravity is still in effect.
Sure am and proud of it.
Man! I've been gone too long. I finally get some time to come back for a
visit and the hottest discussion here is with a left wing DIY'er? :>))
I haven't read every word of every post in this thread (I got a lot of
catching up to do) but the guys here are telling you straight.
The "180 degree thingamajig" you are referring to is called the "J-bend".
The "90 degree whatchamacallit" is called the "waste arm".
There should be NO piece of pipe between the two.
Either lengthen shorten the tailpieces from the sink. Period.
I just got sideways with a couple of really large projects and between
project management and chasing no paying general contractors down for money
I just had no time.
I'm doing a little "restructuring" (see: downsizing) and hopefully life will
return to something a little more "normal". Whatever that is for a
got ya...light the fuse and stand back.
its like pokin at stuff with a stick...funny :-)
libs are sooo easy to piss off.
BTW the job you did is still wrong. And I guess i am hostile agian for
telling you that you made a mistake, that you are wrong.
Are you plae with a very red face??? FAt??
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