Ideal where difficult, complex pipe runs are necessary. The rear end of the fitting, shown below left, features a 1. Size Price Standard In wall skimmer approx 9" wide x 9" Bottom drains for ponds at face with 1. Can still be used mounted in pond base if required. Pressure Flexi - bondable flexible tubing Pressure flexi is a very strong, thick walled PVC based tubing that is reinforced for extra strength.