Aqua Glass One Piece Tub

How much or what do I remove from bottom of tub before install and do I need a mortar base? The tub I removed after thirty years did not have anything under it.
Thanks

>>>How much or what do I remove from bottom of tub before install and do I need a mortar base?<<

I know of no tub that requires the removal anything from the bottom of the tub.
The tub manufactor should tell you if they recommend mortar.

Rarely, they'll have something on the bottom for shipping purposes only, but if so, it should clearly state what's required in the instructions prior to installation. Mortar may not be required or even recommended on some tubs...depends on how it is made. In many situations, the bedding of a tub in mortar makes it both last longer and feel more substantial.