Yes, to add add water via your sprinkler system, just add a valve and link it to the pool fill line. That's what I have, and it works great. Even if I'm not doing it automatically, it's nice to be able to add "an hour" (1.5 inches) of water to the pool. (I use a separate "program" for the pool fill on the sprinkler controller)
I'm not sure why your PB won't do this at no charge... espeically if they are already tearing up and fixing the sprinkler system. I would think it's easier/cheaper than the spigot method.
If you have a "T" going to the spigot, what happens when the sprinkler system fill is running? You may need a check valve. I don't see the need... if you sprinkler fill is out of service, just use a hose.
Robert
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