How do urinal cisterns work?

[Tim Dorrington]

Just daft curiosity... can't seem to find any resource on the web or newsgroups that describes the periodic flushing mechanism (there's plenty of info out there regarding w.c's), and being considerably shorter than 7ft 6ins I can't see inside.

Presumably there's a siphon at work, but how is it suddenly triggered by a very slow trickle of water at the inlet? I always thought you needed a reasonable rush of water to get a siphon started.

Incidentally, I know you can get all manner of electronically triggered cisterns - I'm just referring to the mechanical kind.

It's sad, but please put me out of my misery.

Thanks, Tim.

[Andy Hall]

The simplest ones have an inverted U shaped tube attached to the flush outlet and an inlet valve which allows the cistern to fill at a trickle. WHen the cistern is full enough, water flows through the tube and creates a siphon. This then quickly empties the cistern.

One addon is a solenoid valve on the inlet operated by a timer or by detecting moving people. This means that the cistern only gets filled when the urinal is likely to be used.

[Peter Stockdale]

Hopefully somebody here is planning to check it out in the pub tonite. Can't wait to get their theories - especially after a few pints !!

Pete (fellow saddie)

[Andrew Gabriel]

I vaguely recall this being a requirement now.

[Dave Stanton]

Thats how the one at my place of work, works !!( is that correct ?). And if you live in a hard water area they get furred up constantly.

Dave

[Peter Stockdale]

Quoting you Andy : -

This means that the cistern only gets

First wrong reply IMHO . How many pints consumed ?

More theories awaited !!

Pete

[Peter Stockdale]

Sorry - mis- read your post Andy I am wrong. You are correct Apologies Pete

[Mary Fisher]

I'd like MUCH more information, please.

Mary

[Andy Hall]

Is this penis envy again, Mary?

[Eiron]

So why doesn't the water just trickle out when it reaches the lower edge of the top of the inverted U? I would expect that it needs a push to get enough water over the top of the U to start the syphon.

[Mary Fisher]

Everybody should envy what I have.

Mary

[graham]

Some cisterns are filled through a valve that allows a small amount of water into cistern each time a normal toilet is flushed or a tap is opened.

The valve has a little chamber that fills with a small quantity of water. When the supply pressure to the valve drops when someone flushes a normal toilet or opens a tap, the water in the chamber is discharged into the cistern. The chamber then refills. The advantage is that the cistern only gradually fills when patrons are turning the taps on and off or flushing the toilet.

Graham

[graham]

The very first cisterns worked on a tilt mechanism.

As the tank filled it would tip. Eventually it would tip so far that the water would start to syphon.

Found this on the net:

[Mary Fisher]

Why would they do that? Men don't wash their hands, do they???

Mary

[Mary Fisher]

Mary

[Andy Hall]

The shape of the siphon means that as water trickles over at the start of the flush, air is prevented from re-entering up the flush pipe. The water then running from there down the flush pipe pulls the bubble of air over and down the flush pipe followed by the contents. Remember that these are also mounted high up to assist with the process.

[Andy Hall]

I can't really follow that one :-)

[Mary Fisher]

You're not going to have the chance :-)

Mary

[mike ring]

"Mary Fisher" wrote in news:41991720$0$2657$ [e-mail]:

I wouldn't go there; after a lot of casual bar work, including cleaning bogs for each gender, if your theory is correct the men were not washing their hands, but chucking paper towels in the waste bin thill they overflowed, while the hygeienic females were magically getting washed hands dry magically using hardly any.

mike

[Bob Eager]

Of course they do....

Mind, they wash them FIRST so they don't get their bits dirty!