Pool was originally constructed with two returns. One is at the bottom of deep end of pool. It is a return and not a drain. The other return is at the shallow end of pool. There are two wall skimmers. One is very weak because years ago when a leak was discovered in it I replaced the line by running a new one on the outside of the concrete thereby adding 30 to 40 feet of additional length.
A few years ago I added some additional valves to the system with the idea of sometime being able to use that bottom of the pool return as a drain. I thought that this would make it easier for me to clean the pool when I opened it.
I now have the valves set as originally configure with the bottom as a return. But I can't use it. If I open the wall return and the bottom return the filter pressure drops. If I try closing the wall return and using only the return on the bottom of the pool then there is also low pressure at the filter. It is only when the bottom return is closed and the wall return is open that I get the greatest pressure at the return. So I am stuck with only one return usable and really only one effective skimmer working. Leaves me with poor circulation. I don't know for sure if I am getting sufficient water flow. I assume that when the pressure at the filter is highest that that is when I am getting the greatest flow. I have considered getting a more powerful pump. Can someone explain why the pressure at the filter drops when I open both returns. Do you thing a more powerful pump would work. I currently have Pentair 1 1/2 hp pump.