What kind of water stop screw is better for building pool support formwork?

Hello, now the construction of pool projects with water screws that is to say, three-part water screw is more. But also need to look at the size of the pool, large pool project is recommended to use three-part water screw is better, small pool project is recommended to use ordinary water screw is better.

Three-part water stop screw can be turned over to reuse the outer screw, to overcome the traditional water stop bolt screw can not be reused, cost savings. Demolition is more convenient. Such is the three-part waterstop screw