I am looking to put in two wet shower areas and my plumber has said Wedi are good. looking at buying the the 1400x900 trays and using wedi backer board for walls. I have looked at the wedi kit and see that only water proof tape and cement base flexible adhesive is advised to seal joints etc. I presume the wedi board is fully waterproof but will the adhesive let the tape down if it is not epoxy ? and truly waterproof.
What do I need to use to seal the tape and which adhesive and grouts should i use to remain fully water proof. Also been asked to see if mozaics or pebble mats are ok on a wedi tray. Point loading was my initial concern

Your tape will do its jobs around the joints, its far better than using a paint on kit that could easily puncture. As for the adhesive and grout none of them are 100% waterproof, grout gets wet and dries out the same as mortar.
The difference with your installation is the fact you are using waterproof boards in a wet area instead of ply or plasterboard. Follow the tanking manufacturers instructions and you will be fine.

I have used mosaics in wet areas plenty of times, pebble mats might collect pools of water and be difficult to fit around the trap depending on their size.

Goodluck.

Thanks for the info.

They have all the instructions on their website, its very informative