I have an 18' round above ground Intex pool. I replace filter and pump few years ago with 1hp pump and sand filter. I just installed a through wall skimmer (Hayward) but want to keep the original out flow as well as install a valve switch so I can go from skimmer to wall when needed. I have seen lots of hard plumbed set ups on YouTube , one referenced this site to find proper fittings.
Can you help with sizing ? Which valves to get and best fittings to merge two input lines with a diversion switch?