I have installed a new mixer in the shower, if I open the hot and cold water simultaneously water squirts out of my pressure release valve, if I only open the cold or hot water I do not experience the problem, what can I do to solve this

Can you post a picture of this mixer. Not familer with a shower valve (mixer) having a pressure release valve.

Can you post a picture of this mixer. Not familer with a shower valve (mixer) having a pressure release valve.

The pressure release valve is not situated at the mixer it is situated on the cold water inlet to the geyser (Kwikot), the mixer is a single handle mix, I attached a similar mixer picture. The problem only occurs if I have the hot and cold water running simultaneously

Thanks, I have solved the problem by installing a non return valve after the vacuum breaker on the geyser outlet

We thank you for the update. Always nice to hear back, Cheers, Tom