I have a high CH (520 ppm) and would like to lower using the technique of removing water from the deep end drain and adding water to the shallow end. This would require the I shut off water to the returns and pool cleaner since I do not want water mixing during the process. My waste line is located between the filter and the three way valve. If I shut of water to the returns and pool cleaner I am worried about the back pressure on the pump and filter over the three or four days this process may take. Is it ok to have this kind of back pressure on the pump and filter for three or four days?