Clogged main drain?

[Nate]

Sorry if this has been discussed before....I tried a quick search and didn’t see anything and nothing I’ve found googling really helps...

New to pools, never had one growing up. Anyway, Bought a house alittle over a year ago, pool had stains and mottling when we bought it. I have been roughly maintaining it over the last year while doing a lot of renovations and landscaping etc. now I’m an trying to get the pool sorted out. The pumps runs, skimmer works, vacuum kreeper works as well. I’m wanting to get my chemicals harmonized but before I do I want to use some yellow gone and stain removal agents (allowing a proper amount of time in between of course). This is where my problem starts. The back of the bottles say to try to use the main drain only when using their product. I didn’t really realize my main drain wasn’t working for the last year until I tried messing around with all the jandy valves trying to figure out which one is the main drain because they are not labeled. The house is an ‘88 and I think the pool was out in when the house was built. I’ve figured out my valves now. I’ve got 4 pipes going into the ground...fountains, returns, skimmer, main/vacuum. There lies my problem.
I have one skimmer, one main drain, and 4 jets. I also have one vacuum port with flap on the side that the keeper has been in this whole time. I have figured out which pipes go wear basically but I don’t seem to have a designated main drain...? I have a two port skimmer which sucks water on the deck side of the skimmer the pool side has no water flow. I’ve read that it’s an equalizer port or something from the main drain if the water gets too low. I don’t have a skimmer float valve either. Vacuum works fine, skimmer works fine, but when I turn it to what I would assume would be the main drain or vacuum with the keeper removed and flap shut, I loose water in my pump, it still filled half way but doesn’t stay full. I’m racking my brain trying to figure out why I don’t have a separate main drain valve or why water just barely flows into the pump when the valve is turned to that port. All I have it a pump and filter, two 3-way jandy valves and 4 pipes. Is there something that I’m just missing? I feel like my main drain is clogged because I’ve taken the cover off and no matter which way I turn the valves there’s no suction to the main drain. I’ve tried the drain king in the pump, skimmer, and vacuum port and nothing seems to make a difference. I did try it in the main drain itself for alittle while but the drain king shifted and got stuck half way out and blew alittle while after it expanded and I had to get another. Anyway....ive tried about all I can think of and I can’t figure this out, is there something I’m missing?? Any information or advice on this would truly be a blessing. I’ve tried a drain auger on the scummed side as well but it only goes down so far so I’m not sure if there is a diverter valve under the skimmer or what...

Thank you

[dynamictiger]

but when I turn it to what I would assume would be the main drain or vacuum with the keeper removed and flap shut, I loose water in my pump, it still filled half way but doesn’t stay full. I’m racking my brain trying to figure out why I don’t have a separate main drain valve or why water just barely flows into the pump when the valve is turned to that port.

Not sure from the description however the most likely reason could be the line is simply not used for some time and for some reason has air in it. If there is water trickling into the pump try running it longer perhaps 3-4 minutes and check if the water has increased or run out. This may assist.

Another thought is the 'main drain' may not be a main drain or has been disconnected at some time in the past.

[Teapot]

Its quite typical that the main drain line is the second one in the skimmer. When I say typical, I mean typical of lazy pool builders, you are quite right should be on a dedicated line.
Could you put a hose down the skimmer port and feel the flow out of the main drain? Obviously with the system off.