If its not connected through the skimmer I imagine it's there to empty it. hmmm, on the above. The main drain in pools is for circulating the lower part of the pool and is not intended to drain the pool as in a bath tub.
Would advise that you get a professional to address the situation first hand. The main drain is intrigal to your circulation.
Use the main drain when backwashing, rinsing, or vacuuming. Use skimmer all other times to filter.
Installing swimming pool lights is very difficult. It requires you to drain the water from the pool, and then to drill a place to mount the swimming pool lights.
My pool has two main drain openings, to prevent entrapment. I use a Kreepy Krawly pool cleaner so the main drain stays closed all the time, otherwise, the Kreepy Krawly would get stuck every time it passes over the main drain. There is a valve located with the pool equipment (filter/pump/various valves) which is used to open and close the main drain. I'm no expert, but that's the way mine works.
The valve for the main drain on older pools would be located at or on the equipment pad. You will most likely need a pool tech who knows how to plumb pool equipment to have it changed out. On the other hand if you mean replacing a broken or loose main drain grate then you would have to take the loose or broken grate to your local pool store for an updated version replacement. They will advise from there. k
You don't drain an inground swimming pool, unless you are trained to do so. Doing it alone or even with assistance is extremely dangerous. Save yourself some trouble and go contact a local and trained swimming pool cleaning service.
The purpose of a swimming pool heat pump is to rise the temperature of the water. The pool then can be used for swimming even on days when the weather is not perfect. The swimming pool season is extended.
The pro end of having a main drain is that you spend less time vacuuming the pool. By turning on the main drain only this will help clean the bottom of the pool and results in less overall maintenance time. Also helps clean up any chemical (chlorine, alkaline, shock, etc)that may not have completely dissolved when added to the pool. Also, when winterizing the pool, by having the main drain, you can lower the water level in the pool and still run a recirculating pattern on the filter without destrying the motor. same for opening the pool, can run the pool on main drain cleaning up the winter debris before the pool is completely full.
simple drain a bit of it
You drain the water then plaster the walls from inside