He explains that although the concept was introduced in the U.S. and Canada more than 20 years ago, recently awareness has increased. "Even five years in the past we have been only putting in two to 3 PVC membranes in swimming pools in a month. Now we set up 10 to fifteen per thirty days." Some membranes are available with slip-resistant, embossed surfaces, which are generally used on... http://ezproxy.cityu.edu.hk/login?url=https://progorki.com/modular-pool-system/