Feb 26, 2019 - 06:52 AM
Thank you for contacting Biobidet Support.
You will for sure need at MINIUM of 1.5 inches from the bolt hole to the front of the toilet tank. If you do not, then the bidet base/housing will bump up against the tank and not allow for the proper mounting on the catch plate and your bidet will slide around.
You can also review instructions for measurements on our website as follows:
If you have any further questions please contact us at support.biobidet.com
Source: Toilet Types and Sizes