Syphonic - but not as we know it?

[Plumpplumber]

I'm in the process of trying to sort out a syphonic toilet that works 'hit and miss'. It's a 'Shanks Cavendish' with a ceramic syphon and dates back to 1970. I very carefully separated the cistern from the pan this morning expecting to find an Airex Bomb - but nothing! Instead, there is a chromed pipe which runs from the bottom of the cistern down into the back of the bowl (quite separate from the normal close-coupled flush)

I phoned Lunns - they said they'd never come across such a design and had never heard of a Shanks Cavendish. I then phoned Armitage Shanks themselves and they claimed to know nothing about it either but suggested I talk to a Mr James who reckons that there were some very early syphonic toilets without Airex valves.

Can anyone shed light on this peculiar gizmo? I've Googled 'Shanks Cavendish' and got nothing whatsoever! Meanwhile, I've dismantled the cistern internals and cleaned everything up thoroughly. Amazingly the rubber syphon diaphragm is still serviceable with no splits (other than the four 'criss cross; ones required for it to work) I'm hoping that a reassembly with new washers etc will do the trick.

Anyone come across this beastie?

Pics attached!

 

[stevetheplumber]

its possible the name cavandish was for the syphon rather than the suite its self theres a venturi where the chrome pipe goes into the syphon that causes a vacumn in the tube hence helping to draw the trap on the pan, havent seen one of these for years

 

[Plumpplumber]

its possible the name cavandish was for the syphon rather than the suite its self theres a venturi where the chrome pipe goes into the syphon that causes a vacumn in the tube hence helping to draw the trap on the pan, havent seen one of these for years

So it would work along the lines of a carburettor? OK, so assuming the diaphragm is in good nick there isn't much that can go wrong. I do know that the toilet has worked perfectly for over 40 years because the house belonged to my grandparents and I watched it being installed as a youngster!

I'm going to reassemble this morning and see if it works better. Hopefully a good clean up and replacement of rubbers will have done the trick. I was tempted to just haul it out and replace with a modern toilet but it's well bedded into a drain in a concrete floor (might be fireclay) and I don't want to open another can of worms breaking into that unless I have to. The cistern and bowl are both, amazingly 'as new' without a single chip or watermark.

Thanks for getting back Steve. Anyone else have any experience of this design?

 

[stevetheplumber]

make sure the tube is clear

 

[Plumpplumber]

make sure the tube is clear

Got it all back together and - yes - checked the tube was clear. It's now working as good as new! Probably just rusty crud on the diaphragm and tube.

By the way the pan is 'Cavendish' too - found it way down at the back.

Looks like I'm going to have to overhaul it every 40 years to keep it working properly LOL!

 

[happyflyer]

I know a director on an old plumbers merchant same age as me I will ask him if they stocked this type of syphonic toilet. Like you say it will work forever.

 

[Plumpplumber]

I know a director on an old plumbers merchant same age as me I will ask him if they stocked this type of syphonic toilet. Like you say it will work forever.

Thanks! I'm intrigued that it can't even be traced on Google and Shanks themselves didn't have a clue! Sounds like a collector's item.

 

[happyflyer]

I think it might have been a anti syhon device to stop the trap been broken after all they were normally 3.5" dia

 

[stevetheplumber]

I think it might have been a anti syhon device to stop the trap been broken after all they were normally 3.5" dia

you think wrong then

 

[Plumpplumber]

you think wrong then

Steve's venturi theory sounds about right. There's a sort of internal bridge across the flushpipe where the chrome pipe branches off. It seems to draw from the centre of the stream. The flushpipe is also slightly bulbous at this point, presumably to assist the venturi effect. So the chrome pipe will effectively act as a suction pipe I suppose which in turn instigates the syphonic action in the pan.

One thing that puzzled me was how the pipe is connected into the pan. It looks like the sort of connector you'd use in a cistern for say an overflow - with a backnut. BUT the backnut must be up inside the trap somewhere and I haven't a clue how you'd get at it!