draining new_to_me pool : CYA>100 PH>8

[cardano]

Hi Gang.
So the house I bought has a wonderful pool, but since it sat idle for three months between when the sellers left and we bought it, the pool water looks like it needs to be changed out. CYA over 100, PH over 8, that sort of thing.
Good news is the hayward vari flo valve has both a backflow ( so I can clean the DE filter which probably needs it ) and a Waste setting which is piped to sewage. YAY!
Bad news is it looks like the main drain was disconnected as the 1 skimmer I have features a return to the pump and a second port on the bottom which I would expect to go to the main drain.
But there is no suction whatever on the main drain line, so I figure it was disconnected as the pool might be as much as 30 years old ( relatively recently remodeled pebble tech at least )

My plan would be to use a vacuum hose to extend the skimmer suction to the bottom of the pool and 'waste' away.

Given that I am in Phoenix and up on North Mountain a bit, I dont figure a high water table will be an issue ( although we did just have 3 " of rain last weekend so I will be waiting till next weekend to do this drain )

Still. Once I figure out an actual CYA reading, and a reading on the unfortunately hard water that I will be adding in to the pool from the tap
I should have a much better understanding of how much of the water will actually need to be removed before I can start filling it again.

My question is : aside from ensuring that I maintain a good seal at the vacuum/skimmer attachment (probably by leaving a garden hose running a little water into the skimmer, is there anything that I am forgetting?

Thanks in Advance,
Cardano.

 

[jblizzle]

Both of my pools have had the floor plumbed into the 2nd port in the skimmer. You should not be able to sense any flow through the main drain line. You would need a skimmer float diverter to put in the bottom of the skimmer under the basket to force the suction to come from the floor.

How did you get the CYA level of >100? If you have your own recommended test kit, you can use a 50/50 mix of pool and tap water to start, add the reagent, then outside with your back to the sun pour into the tube at waist level. You can pour back and forth a few times to see if you are consistent. Then double the reading for a rough idea of how high the CYA level is.

Your tap water has 0 CYA in it, and the pH has nothing to do with needing to replace water. I would guess your CH is also high, but likely the CYA is the biggest issue that required water replacement.

You are also right that ground water is not likely an issue.

What you are proposing w as far as using a hose to drain the pool might work, but the pump may lose prime when the water gets much below the pump level. you can rent a submersible pump from Home Depot for under $50 and it will drain it a lot faster.