Greetings all, I'm hoping you can help me solve a problem for my dad:
Having recently extended his bathroom, the toilet (old thing, wall mounted cistern, but at normal height with a flush handle, not overhead with a chain) has gone from an external overflow to no overflow.
Some research on the internet confirmed that you can now get syphons with an overflow built in. Unfortunately, the shortest one commonly available (8 inch, I think) has the overflow level about 2 inches above the normal water level in the cistern (although it does fit ok and flush okish).
The toilet clearly needs a working overflow. Can anyone tell me if a shorter syphon is available to work with older, shallower cisterns? Or is there a downpipe available that incorporates an overflow to dispose of excess water via the toilet itself?
There are various different models on the market that may do what you need.
There are, as far as I am aware, only two heights of syphon on the market, and the 8" is the shortest. Older cisterns tend to be wider than newer models so the water in them is shallower which creates the problem you mention as they were never designed to have internal overflows. It was against water regs up until recently. You can of course lead the overflow away to a bath trap for example.
It is not possible to connect any separate mechanism to a syphon to act as an overflow because it would stop the syphon from working.
With the overflow height, you just cut it off at the height required.
I can't see how the overflow can be connected into the pan anywhere. I assume the toilet is a low level with a "L" shaped flush pipe? Well, anyway, if you tried to connect the overflow into the flush pipe, it would stop the syphon and the toilet just wouldn't flush at all.
As I see it, there just is no other choice other than replacing the cistern. Is it plastic? they aren't necessarily that expensive you know?