Hello. We are very sorry to hear that! There really isn't a standard opening, all bathrooms are different depending on how the plumber has plumbed the unit. You should be able to consult a local plumber to assist you with making it work. This section of Houzz is for product questions and we cannot see any of your order information, if you would like to contact us further please go to your orders and you can contact us directly from there and we will try to help you with a solution. Thank you!