Syphon height sizing

[andytw]

Hi,

The syphon in my Twyfords toilet has packed in. It is marked Caradon and measures 11" from top to bottom.
I am going to try and source a diaphragm for it before replacing the whole unit but just wondering about the size as I see various sizes are available. Am I right in that the size only needs to be, say, an inch or so above the water level.
My cistern is quite tall, at 14", but the top of the syphon is around 4" above the water level which is 7" deep.

Just seems to me that the higher the syphon, then the more effort is required to start the flush.

Thanks,

andytw

 

[Charnwood]

The vast majority of cisterns that have syphons fitted leave the factory with 71/2" syphons nowadays.
Also, most are adjustable for a 6, 7 and 9 litre flush.

Fit a flapper valve.