Just bought a 4040 system for my brother put it together .but I can not seem to get the water tds down below 40ppm. I live on the same street have a the same 4040 system and at low pressure mine comes out at 6ppm and 3ppm at high preassure.the only difference is his system is a new membrane that is designed to work better a low pressure. Has any one any thoughts. I left it running for an hour today. Do the membranes have to go in a certain way?