My pool had one when I bought the house. I can see how it prevents sucking air if the water level drops below skimmer intake level and so that's all I ever expected from it. I never really inserted it either unless I had an expectation the water level would be low for some reason (like when I've had to shut off auto fill due to a well system issue).Sherlock,
Some people have good luck using floating diverter valves, but I have not.
I have never gotten them to reliably work for more than a day at most..
I just gave up even trying.. I have two rent house pools that no longer have operating main drains.. They have been this way for over 10 years and they operate every bit as well the pool at my house, that has a main drain.
In my opinion, main drains are just useless in most cases.. In well over 10 years of operation on my three pools, I have never had the water drop below the skimmer's mouth.
In any case, I hope yours works well for you.. But if not, I would not spend 5 minutes even thinking about it..
Just curious.. Why did you buy one???
Thanks,
Jim R.
Sherlock,
You have one main drain that has two covers...
Since it is connected into the bottom of the skimmer, it will never work unless there is an operating floating diverter valve.
Even if you get the main drain working, you will never be able to tell any difference in the way the pool works..
Thanks,
Jim R.
So how can one meaningfully adjust the flap, if there's no way to actually assess or measure the flow into the drains at the bottom
One cannot. But that's just because flow into the main drain is not meaningful.
You don't need the main drain for normal operation of the pool. In fact it's better for all the flow to be through the skimmer. If you think of the main drain as only there for backup -- for supplying water to the pump when the skimmer is clogged or empty -- you can do what I do and leave the flap completely open.
But do test the operation with the float closed, just to make sure that the line from the main drain to the skimmer is free of obstructions.
Sherlock,Except (like many pool topics!) there's a diversity of opinion: