When we are discussing installing our equipment with a client, we always insist that the equipment is installed on a bypass line. Most of our clients “get” it but some don’t quite grasp the concept. A bypass line is a separate plumbing loop taking off – and returning to – the main plumbing line so that it can be 100% isolated; allowing the given piece of equipment, on the bypass to be maintained while the pool continues to circulate and be open for use.
It makes no sense to have to close your pool down to clean the electrolytic cell stack, or the quartz sleeves on your UV system. If all you need to do is close 2 valves, and open one to give yourself the luxury of taking time to complete your maintenance in a thorough and unhurried manner.
I feel the same way about unions, and true union ball valves. Can’t tell you the times I have seen a large piece of equipment plumbed into a ridged plumbing line; removing and replacing that piece of equipment now means having to cut the lines where if there was a union or true union valve the process would be cleaner, easier and cheaper.
Planning ahead is a lot more effective than wishing that you had.