Anything with a tank is gravity powered. Incoming water, AFAIK, has nothing
to do with flushing, just refilling the tank. I'll bet those old "Godfather
I" type toilets with the ceiling-high tank could flush a bag of golf balls.
Some tankless toilets run off water pressure, but I've not seen them (here
comes the flood of those that have!) in anything but commercial structures.
When I bought my toilet the sales girl referred to it as the "super
flusher". Recently, I heard the rest of the story. The boys with bling
had been coming in and asking for it that way. Word is the cops hate it!
Not quite. Some toilets and urinals have flushometers, that use water
pressure, common in nyc apartments, and maybe there are other
arrangements, but some other tank toilets are playing tricks on the
**Yes, I had a particularly loud toilet in a motel, so I took the lid
off and there was some metal chamber with a distorted dome top filling
the space. I guess it filled up the bladder with water pressure,
compressing some air inside, and used that to flush. It's a good
thing I was alone or it would have woken me every time it was used.
The water can only fall at a certain speed though a given
diameter...no matter what height.
At least, that's how I see it. If there was a column of water and it
was release at the bottom...then you would see some pressure.
On Thu, 3 Feb 2011 09:59:37 -0800 (PST), Bob Villa
Yes, but is the maximum speed reached when the bottom of the tank is
an inch above the toilet, and the top of the water in the tank is
about 12 inches higher than that? If not, wouldn't having a higher
tank mean a speed closer to the maximum? Since the height of the
water averages about 7 or 10 times as much with the tank right on th
I"ve used those toilets of course, but not since I started paying
attention to this sort of thing.
I'm with you because when I test flush my toilet, higher is better in terms
of getting it to flush with a minimum amount of water in the bucket. I
suspect that as toilet design improved, they found the ceiling high tank
didn't need to be quite so high to do the deed. In looking up the history
of toilets, there are tank type units that DO use pressure to flush:
Tank style with high-pressure or pressure-assist valve
This system utilizes mains water pressure to pre-pressurize a plastic tank
located inside of what otherwise appears to be the more typical ceramic
flush tank. A flush cycle begins each time a user flushes the bowl. After a
user flushes and the water in the pre-pressurized tank has finished emptying
into the bowl, the outlet valve in the plastic tank shuts. Then the high
pressure water from the city main refills the plastic tank. Inside the tank
is an air-filled balloon-like rubber diaphragm. As the higher-pressure mains
water enters the tank, the rubber diaphragm is also pressurized and shrinks
accordingly. During flushing, the compressed air inside of the diaphragm
pushes the water into the bowl at a flow rate which is significantly higher
than a tank style gravity-flow toilet. This system requires slightly less
water than a gravity-flow toilet. Pressure-assist toilets are sometimes
found in both private (single, multiple and lodging) bathrooms as well as
light commercial installations (such as offices). They seldom clog, but the
pressurized tanks require replacement about once every 10 years. They also
tend to be noisier - a concern for residential settings. The inner bowl
stays cleaner (in appearance) than gravity counterparts because of the
larger water surface area and the toilet's forceful flush. Newer toilets
from several companies such as Kohler that are pressure-assisted use 1.4 US
gallons (5.3 l) to 1.1 US gallons (4.2 l) per flush.
Whether the "flushometer" toilet is truly a "tank type" toilet is open to
debate. You learn something new everyday. What surprised me was how old
the flush toilet is: circa 26th century BC. I wonder how many times
toilets have been flushed since then?
Very interesting webpage. I may have told this story before, but
there are a lot of new people here, and I have questions this time.
In NYC I read or was told that every building above 6 or 8? stories
had to have a water tank on the roof so that there would be adequate
water pressure. Often you can see the tank but often they build
simple walls around it. Sometimes the tanks are inside the top floor.
Tanks are expensive iiuc because the roof has to be made strong enough
to support them. (So a lot of buildings were/are? built just shy of
the tank requirement height.) I've always wondered about this since
NY, Brooklyn, and the Bronx** at least have hills, and I would think
the absolute height of the building would be more important than the
height relative to the street it's on. ??
**Staten Island has hills but not many tall buildings.
Buildings four stories or less can use normal water pressure. Not
sure what determines the water pressure. The opening of the water
tunnels from the Catskill mountains are much higher than 80 feet, I
think, so it must be something inside NYC. ??
An inordinately large number of buildings are 6 stories. Few are 5
because the water requirements for 5 are the same as for 6, and many
are only 6 because I think at 7 stories is when the water requirements
increase) Buildings more than 4 stories and less than the height that
requires a roof tank have to have two pumps and a water storage/
transit tank. One pump pumps the water into the tank against air
pressure from the air in the tank. The second pump adds air to the
tank, to replace that which is gradually absorbed by the water. In
normal circumstances the air pump would only run once every 3 to 8
days, for maybe 15 minutes or an hour. It was automatic too, although
I don't remember what turned it on.
I don't know if any tanks have rubber bladders. I sort of think not,
but certainly the book I read didn't illustrate one and my building
built in 1930 didn't have one.
My landlord was an immigrant from a fairly poor country in Europe. Or
at least he wasn't very knowledgable about stuff. He became a
"plumber" when there was a big demand for them in NYC when landlords
were no longer allowed to burn trash in furnaces not designed to do
that, and uncompacted trash could not be thrown away by apartment
buildings above a certain size. The trash compactors were water
powered, so he became a "plumber".
I'll give him credit that he wasnt' content to remain a plumber. By
the time I met him, he owned 3 or 4 buildings small to medium sized
apartment buildings, all but ours almost a slum, partly because he was
the landlord. Left unchecked, he might have turned our building into
a slum too, but there were too many tenants who could stop him. He
lived in Long Beach, Long Island, a fairly small area but one with
poor, middle, and almost rich neighborhoods. I didn't know and didn't
want to know which he lived in, because I didn't want his apparent
economic situation to influence my attitude towards him. I wanted it
to be just legal and contractual.
But most of the tenants didn't know about the water situation** and
only those on the 6th floor of the 6-story building really cared, plus
a few on the 5th floor (mine worked pretty well really, but once in a
while I had to flush two or three times. Mostly it annoyed me that he
didn't know how to do things right. Oh, and when I was taking a shower
and someone flushed the toilet, the shower became scarily hot. I think
that wouldn't have happened if there had been local air pressure to
boost the cold water flow. I switched to baths because of this.)
Anyhow, I think I once turned the air pump on and it seemed to be
working. I think he didn't understand what the air pump was for so
afaik he never used it -- the switch was always off -- and he had to
run the water pump all the time -- the switch was never on automatic.
So it ended up net-costing him money for electricity I think. I
photocopied a page from the book I mentioned and sent it to him with a
note, but I never heard back and I don't think it sank in.
**I only knew about the water because I spent time wandering around
the big basement and looking at everything. There was no stairway,
except outside, but the basement used to be available to everyone via
the elevators. Someone must have done something to annoy him there,
and when he put an electric-key-lock on the button that took the
elevator to the basement, I waited until the middle of the night, took
out the four big brass screws that held the brass control panel
escutcheon in place, and attached some lamp cord to each side of the
key switch, then ran the wire to just under the edge of the plate when
I put it back on. It wasn't visible unless your eye was below 40
inches, and even then it wasn't really noticeable. It stayed this way
for years, until some time after I moved out. I wonder if Alex figured
out who put it there!
The floor-button-current was low-voltage and after I did this, I could
hold a quarter or anything metal to the end of the lamp cord and
bypass the key-switch, and go to the basement. I didn't steal anything
or do anything bad. Mostly I needed this in case a fuse blew in the
middle of the night -- this happend fairly often since the 3-bedroom
apartment had only two fuses, both 15 amps, and both fed from a 20-amp
fuse in the basment. Now I'm sure this would be a violation of code,
but I think it was grandfathered in buildings of the era of mine.
Anyhow, the fuse in the basement blew more often than the ones in the
apartment, and I didn't want to wake the super or bother him after
5PM. I used to go down there to explore too.
If anyone asks, I'll tell you about my exploration of the furnace
room, a story in itself.
I think that a firecode thing more than anything else. As firetrucks hook
into the watermains the overall pressure drops. I could be wrong, though -
it's just a guess.
I do know that more than one water tower in NYC has been converted to living
quarters. Whether that's legal or not, I don't know. I've watched them
replace old water towers on "Dirty Jobs" but that's about all I know about
Sure. Even it if puts my reputation as the group's most verbose poster at
risk. (-: Sorry I can't answer your other questions. I am sure we have
someone here who knows.
Actually, the calculations are widely available as they are used in
irrigation, amongst other applications. There is not a lot of head loss
for that large a pipe. Velocity being a factor of pressure, area and
resistance. The restrictions largely seem to be in the toilet itself,
not the water column.
I think the key is a direct path to flush the effluent rather filling
up the bowl. In a poorly designed toilet the bowl will fill and that
height of water in the bowl will push out the waste. Sort of like tuning
exhaust lines in a car.
They called them high suite combinations and the later toilets were low
Having a high tank has some advantage, it is a big tube and will be
full of water when it hits the bowl. But technology moved on.
Like Bob, I'm not
No. They use modern toilets, the Kohler Cimmaron 1.2.
The height absolutely makes a difference in pressure. In my "super
flusher", the tank fills all the way up, but it does not drain all the
way down (unless you hold down the handle). The minimum column height is
What I think is more important is how it drains. If it doesn't drain
well the bowl simply fills instead of flushing away. The weakest link is
in the draining, not the filling, although both need attention.
Ive noticed that nothing sticks to my toilet bowl, so resistance is
less there also. You are trying to flush solids not water. The water
path in my "super flusher" is directly in line with the waste. That is a
direct flow, with the waste in the middle.
So, what I am saying is that while more pressure is good, it is not
the answer. Good design is.
On Fri, 4 Feb 2011 05:08:04 -0800 (PST), Bob Villa
Pressure that would show itself in the speed of the water swirling in
the tank. Seems to me it's like trying to wash the grass cuttings
off the driveway with a garden hose at full blast, versus one whose
pressure is cut because the spigot opening is 3/4 closed.
We can get by with low tanks and low pressure because the toilets are
better designed, and don't usually need the greater pressure of the
higher tanks, isn't that it?
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