Replacement Pneumatic Button Results in a Poor Flush Drainage and wastage systems and plumbing help, advice and answers

[eadalam]

Hi
Not a plumber, so please be gentle.
Recently the pneumatic flush button in my toilet broke and I had to source another at short notice.
The original button worked perfectly and you only had to touch it once to get a full flush. Unfortunately the replacement button doesn't seem to have enough power to fully lift the cistern drain and the button has to be held in until the cistern is empty. The result of this is a very weak flush that struggles to remove even a single piece of toilet paper.
If I lift the cistern drain by hand then the flush works perfectly.
The replacement button I purchased is a GROHE 38488000 and I'm wondering if this model is known for having insufficient pressure, or air volume to fully lift the cistern drain?
Can someone recommend a better button?

[Plumbog]

Hi eadalam
Is this the correct button for the cistern? Do you have a grohe cistern installed. Different manufacturers may use different sized hoses to connect the button to the flush valve so worth checking the hose is a good fit, another thing to check, remove the hose from the back of the button and cover the nozzle on the back of the button, press the button to ensure you are getting a resistance, if you are not there may be an issue with the button. Those buttons have air bellows like this inside https://buyplumbingonline.co.uk/grohe-a ... 13219.html
If the button and hose are both okay there is normally a bellow inside the flushvalve which could be at fault.
See how you get on with the hose and button and if both are fine send attach some pictures of the cistern valve see what model it is.