As received, a Jandy three-way valve gives one the option to open/close two out of three ports. By unscrewing the top, repositioning the 'inlet' marked on the cover to the back of the valve (where there is no port), and replacing the cover you now have the option to open/close three out of three ports.

Is this OK? Advisable? In my case, this is a three way Jandy valve located shortly before Intelliflo pump intake; by making the third port closable I can not only pull water from either of the two ports, but also close the third port (pump intake) to isolate the pump for cleaning etc. Is this OK? All help much appreciated...