My weird sink drain

This is totally OT for this group -- except the group contains a lot of
obviously clever people who are professionally interested in aerodynamic
and fluid flows and pressures, pipes, valves, and the like, and maybe
someone will be entertained by the following odd bathroom sink behavior.

Our newly remodeled bathroom has a circular glass above-counter sink
like a hemispherical glass salad bowl, about 18" in diameter at the top
and 7" deep, with a push down-pop up drain plug in the bottom center,
and a pretty high capacity faucet above it. Standard elbow fitting and
drain pipe going into the wall underneath the sink and counter top.

With the drain open, turn the faucet on full force: water gets dumped
into the sink considerable faster than it can drain out and the water
level in the sink rises rapidly up to the rim, on the verge of
overflowing, in 20 or 30 seconds.

At the last second turn the faucet part way off -- down to roughly 50%
of full flow, more or less -- then trim the flow until inflow rate just
equals outflow, so the water level stays just 1/4 inch or so below the
rim. Then leave it in this steady-state condition, and wait.

For approximately *eight minutes* (by the watch) the resulting situation
remains perfectly stable, with water level hovering just below the
overflow point. Then, all of sudden, water level starts dropping.

Turn faucet back up to full flow. Water level continues dropping, keeps
dropping faster in fact, until sink is essentially empty, and the full
force input that initially caused the sink to fill now roars down the
drain with only 1/2' or so of water swirling around the drain in the
bottom. This continues as long as I want to watch.

This doesn't seem to result from just blowing some temporary clog out of
the drain: I've repeated it three times, several hours apart, with
essentially identical behavior.

I'm at a loss to explain how it happens, except to hypothesize that
maybe there's some point underground and quite a ways further down the
drain where the drain pipe has a long slow rise, then a drop, and in
some way the initial slower flow has to fill the rising section until a
siphon action gets going over the top?

That doesn't really sound persuasive, however. Anyone have any other
ideas?

AES wrote in news:siegman-11B9F7.19492611042006
@news.stanford.edu:

This is totally OT for this group -- except the group contains a lot of
obviously clever people who are professionally interested in aerodynamic
and fluid flows and pressures, pipes, valves, and the like, and maybe
someone will be entertained by the following odd bathroom sink behavio

Snipola of rest

You filled the pipe to the point it starts acting as a siphon.

I've seen my shower do it. I'm on the second level. I have one of
them 'water saver' heads so you know the flow is slow. I get about
an inch of water in the tub anyway. After several minutes, it
starts draining and stays that way.

Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html
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Sed quis custodiet ipsos Custodes?

Improper vent installation.



"AES" wrote in message
...
| This is totally OT for this group -- except the group
contains a lot of
| obviously clever people who are professionally interested
in aerodynamic
| and fluid flows and pressures, pipes, valves, and the
like, and maybe
| someone will be entertained by the following odd bathroom
sink behavior.
|
| Our newly remodeled bathroom has a circular glass
above-counter sink
| like a hemispherical glass salad bowl, about 18" in
diameter at the top
| and 7" deep, with a push down-pop up drain plug in the
bottom center,
| and a pretty high capacity faucet above it. Standard
elbow fitting and
| drain pipe going into the wall underneath the sink and
counter top.
|
| With the drain open, turn the faucet on full force: water
gets dumped
| into the sink considerable faster than it can drain out
and the water
| level in the sink rises rapidly up to the rim, on the
verge of
| overflowing, in 20 or 30 seconds.
|
| At the last second turn the faucet part way off -- down to
roughly 50%
| of full flow, more or less -- then trim the flow until
inflow rate just
| equals outflow, so the water level stays just 1/4 inch or
so below the
| rim. Then leave it in this steady-state condition, and
wait.
|
| For approximately *eight minutes* (by the watch) the
resulting situation
| remains perfectly stable, with water level hovering just
below the
| overflow point. Then, all of sudden, water level starts
dropping.
|
| Turn faucet back up to full flow. Water level continues
dropping, keeps
| dropping faster in fact, until sink is essentially empty,
and the full
| force input that initially caused the sink to fill now
roars down the
| drain with only 1/2' or so of water swirling around the
drain in the
| bottom. This continues as long as I want to watch.
|
| This doesn't seem to result from just blowing some
temporary clog out of
| the drain: I've repeated it three times, several hours
apart, with
| essentially identical behavior.
|
| I'm at a loss to explain how it happens, except to
hypothesize that
| maybe there's some point underground and quite a ways
further down the
| drain where the drain pipe has a long slow rise, then a
drop, and in
| some way the initial slower flow has to fill the rising
section until a
| siphon action gets going over the top?
|
| That doesn't really sound persuasive, however. Anyone
have any other
| ideas?

Plugged (partially)roof vent/stack.

John

AES wrote:

This is totally OT for this group -- except the group contains a lot of
obviously clever people who are professionally interested in aerodynamic
and fluid flows and pressures, pipes, valves, and the like, and maybe
someone will be entertained by the following odd bathroom sink behavior.

Our newly remodeled bathroom has a circular glass above-counter sink
like a hemispherical glass salad bowl, about 18" in diameter at the top
and 7" deep, with a push down-pop up drain plug in the bottom center,
and a pretty high capacity faucet above it. Standard elbow fitting and
drain pipe going into the wall underneath the sink and counter top.

With the drain open, turn the faucet on full force: water gets dumped
into the sink considerable faster than it can drain out and the water
level in the sink rises rapidly up to the rim, on the verge of
overflowing, in 20 or 30 seconds.

At the last second turn the faucet part way off -- down to roughly 50%
of full flow, more or less -- then trim the flow until inflow rate just
equals outflow, so the water level stays just 1/4 inch or so below the
rim. Then leave it in this steady-state condition, and wait.

For approximately *eight minutes* (by the watch) the resulting situation
remains perfectly stable, with water level hovering just below the
overflow point. Then, all of sudden, water level starts dropping.

Turn faucet back up to full flow. Water level continues dropping, keeps
dropping faster in fact, until sink is essentially empty, and the full
force input that initially caused the sink to fill now roars down the
drain with only 1/2' or so of water swirling around the drain in the
bottom. This continues as long as I want to watch.

This doesn't seem to result from just blowing some temporary clog out of
the drain: I've repeated it three times, several hours apart, with
essentially identical behavior.

I'm at a loss to explain how it happens, except to hypothesize that
maybe there's some point underground and quite a ways further down the
drain where the drain pipe has a long slow rise, then a drop, and in
some way the initial slower flow has to fill the rising section until a
siphon action gets going over the top?

That doesn't really sound persuasive, however. Anyone have any other
ideas?

Probably the old "draw tube" trick. The flow is slow at first until the
downcomer pipe below fills up. Then the "head" or weight of water in the
"draw tube" exerts a negative pressure on the top of the drain. To help
explain this, the pressure at the bottom of the downcomer (waste pipe) is
atmospheric pressure, so the pressure at the top must be less by however
many feet of pipe are full below it, about 0.5 psi per foot.

Rod
"The Visitor" wrote in message
...
Plugged (partially)roof vent/stack.

John

AES wrote:

This is totally OT for this group -- except the group contains a lot of
obviously clever people who are professionally interested in aerodynamic
and fluid flows and pressures, pipes, valves, and the like, and maybe
someone will be entertained by the following odd bathroom sink behavior.

Our newly remodeled bathroom has a circular glass above-counter sink like
a hemispherical glass salad bowl, about 18" in diameter at the top and 7"
deep, with a push down-pop up drain plug in the bottom center, and a
pretty high capacity faucet above it. Standard elbow fitting and drain
pipe going into the wall underneath the sink and counter top.

With the drain open, turn the faucet on full force: water gets dumped
into the sink considerable faster than it can drain out and the water
level in the sink rises rapidly up to the rim, on the verge of
overflowing, in 20 or 30 seconds.

At the last second turn the faucet part way off -- down to roughly 50% of
full flow, more or less -- then trim the flow until inflow rate just
equals outflow, so the water level stays just 1/4 inch or so below the
rim. Then leave it in this steady-state condition, and wait.

For approximately *eight minutes* (by the watch) the resulting situation
remains perfectly stable, with water level hovering just below the
overflow point. Then, all of sudden, water level starts dropping. Turn
faucet back up to full flow. Water level continues dropping, keeps
dropping faster in fact, until sink is essentially empty, and the full
force input that initially caused the sink to fill now roars down the
drain with only 1/2' or so of water swirling around the drain in the
bottom. This continues as long as I want to watch.

This doesn't seem to result from just blowing some temporary clog out of
the drain: I've repeated it three times, several hours apart, with
essentially identical behavior. I'm at a loss to explain how it happens,
except to hypothesize that maybe there's some point underground and quite
a ways further down the drain where the drain pipe has a long slow rise,
then a drop, and in some way the initial slower flow has to fill the
rising section until a siphon action gets going over the top? That
doesn't really sound persuasive, however. Anyone have any other ideas?

"Jim Macklin" wrote in message
news:Hs3%f.3012$8q.1738@dukeread08...
Improper vent installation.

Good chance that is the case.

The vent is supposed to be in a vertical run of pipe, not in the horizontal,
and it is allowing water to have to pull the full cross sectional area of
pipe, without air replacing it, and water flowing in the bottom.
--
Jim in NC

I think a lot of people are going to Home Depot or Lowes and
doing their own plumbing and not following CODE. A
qualified plumber can tell pretty quickly what the problem
is, but a fix can involve considerable re-work if new vent
pipes must be run.


--
James H. Macklin
ATP,CFI,A&P

--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.
some support
http://www.usdoj.gov/olc/secondamendment2.htm
See http://www.fija.org/ more about your rights and duties.


"Morgans" wrote in message
...
|
| "Jim Macklin" wrote
in message
| news:Hs3%f.3012$8q.1738@dukeread08...
| Improper vent installation.
|
| Good chance that is the case.
|
| The vent is supposed to be in a vertical run of pipe, not
in the horizontal,
| and it is allowing water to have to pull the full cross
sectional area of
| pipe, without air replacing it, and water flowing in the
bottom.
| --
| Jim in NC
|

"Jim Macklin" wrote

I think a lot of people are going to Home Depot or Lowes and
doing their own plumbing and not following CODE. A
qualified plumber can tell pretty quickly what the problem
is, but a fix can involve considerable re-work if new vent
pipes must be run.

Fortunately, a popup kind of vent is now available and legal (in most cases)
and the venting can be had with a minimum or "surgery."

You are right about the non-code bit, and also would be surprised at what
does pass, even when it is inspected.
--
Jim in NC

"AES" wrote in message ...
This is totally OT for this group -- except the group contains a lot of
obviously clever people who are professionally interested in aerodynamic
and fluid flows and pressures, pipes, valves, and the like, and maybe
someone will be entertained by the following odd bathroom sink behavior.

Our newly remodeled bathroom has a circular glass above-counter sink
like a hemispherical glass salad bowl, about 18" in diameter at the top
and 7" deep, with a push down-pop up drain plug in the bottom center,
and a pretty high capacity faucet above it. Standard elbow fitting and
drain pipe going into the wall underneath the sink and counter top.

With the drain open, turn the faucet on full force: water gets dumped
into the sink considerable faster than it can drain out and the water
level in the sink rises rapidly up to the rim, on the verge of
overflowing, in 20 or 30 seconds.

At the last second turn the faucet part way off -- down to roughly 50%
of full flow, more or less -- then trim the flow until inflow rate just
equals outflow, so the water level stays just 1/4 inch or so below the
rim. Then leave it in this steady-state condition, and wait.

For approximately *eight minutes* (by the watch) the resulting situation
remains perfectly stable, with water level hovering just below the
overflow point. Then, all of sudden, water level starts dropping.

Turn faucet back up to full flow. Water level continues dropping, keeps
dropping faster in fact, until sink is essentially empty, and the full
force input that initially caused the sink to fill now roars down the
drain with only 1/2' or so of water swirling around the drain in the
bottom. This continues as long as I want to watch.

This doesn't seem to result from just blowing some temporary clog out of
the drain: I've repeated it three times, several hours apart, with
essentially identical behavior.

I'm at a loss to explain how it happens, except to hypothesize that
maybe there's some point underground and quite a ways further down the
drain where the drain pipe has a long slow rise, then a drop, and in
some way the initial slower flow has to fill the rising section until a
siphon action gets going over the top?

That doesn't really sound persuasive, however. Anyone have any other
ideas?


Even though the faucet is not touched, is the inflow rate changing? Maybe depleting a well pump?

Morgans wrote: some stuff about venting.

I'd believe that is the case.
I once had an old, old, oooold house with a kitchen sink that didn't
have a vent. And it was a BIG sink. When you pull the plug on that
granny, it took the wash rag right with it, and me with both feet in
the sink pulling back! The whole sink drained in only 3 or 4 seconds,
and gurgled for a while after that.