Twyford flow cisterne fitting instructions - Toto CST414M-51 Aquia Dual Flush Close Coupled Elongated Toilet - Ebony

50 years old
no spares available
time to up grade the cistern

open the cistern and if the water is from the over flow pipe , fit new washers in the float control
if the water is down then replace the flush washers at the bottom on the cistern

adjust the float setting or the setting on the unit around the inlet pipe
this is achieved by screwing up or down on the threaded section read the instructions as you may have to fit a pressure regulator before the cistern tap if utility pressure exceeds the desired operating pressure of the cistern

there is a spring under button or a weight replace it or re balance it

Push in the sides of the cistern at the top, the buttons are fixed to the top and come away with it. Instruction and fittings are inside.

replace the whole control unit
There may be 2 problems
the small washer that shuts off the water flow when the level is reached may be swollen and not sealing properly
the section at the bottom has cracked at a thread level
so by replacing the unit you will eliminate both problems
to remove the unit, turn off the water tap, flush the system, holding the button down until all of the water has gone
remove the inlet pipe at the bottom of the cistern
undo the retaining nut under the cistern and lift the control unit out
there will be water in the bottom of the cistern so use old towels on the floor to soak up the water that will run out

Assuming the seal washer is inside the cistern and there are no cracks in the cistern itself you could apply a silicon sealant to the seal washer inside the cistern.

hi i would suggest your ball valve in the cistern needs ajusting remove the top of the cistern you will see the ajustment screw at the end fo the ball **** arm hope this helps

i presume with lid of u can flush toilet by pusshing switch with finger if so buttons must be spot on when replacing lid can be adjusted inside systern any probs get back

sounds like you either have a leak or the water is returning into the cistern thus filling the lines with air and you getting a blast of air and water. I don't know much about them but logic tells me there should be some type of valve that keeps the water from back flowing into the cistern.