High cya and partial drain questions as never done before

[Julie8000]

Newby here and my husband and I are not sure what to do. In reading I see we need to deal with cya to get everything in line and convert to liquid chlorine. Will need to buy as we haven’t used before.

In ground pool 11,500 gal gunite Just got the K2006c test kit. Our cya is close to 175. Our fc is 4.8 ph 7.6 Ta 180 Ch 250. Had been using shock and tabs. We need to drain water and refill quite a large volume but we have never done it and want to be sure we do it correctly. We have 2 skimmers, and a main drain valves at equipment pad with back wash to sewer line. we will need to drain quite a bit but reading about below skimmer lines and pump prime and not sure what steps to follow. we have algae on steps and side. Can’t get the pictures of equipment to load. The filter and pump info in my signature. We are on city water.

 

[mknauss]

Welcome to the forum!
Did you do the dilute method to get your CYA level?
In Houston, draining can entail risk to the pool structure. Do you know if you have shallow water table? Near a bayou, lake, etc?
You will want to get a separate pump to drain. If you can drain at least half the pool volume safely, then renting a pump from Home Depot is the best idea. You do need to find out where the water you pump out is allowed to be sent.
I suggest you read ABC's of Pool Water Chemistry.

 

[Julie8000]

Welcome to the forum!
Did you do the dilute method to get your CYA level?
In Houston, draining can entail risk to the pool structure. Do you know if you have shallow water table? Near a bayou, lake, etc?
You will want to get a separate pump to drain. If you can drain at least half the pool volume safely, then renting a pump from Home Depot is the best idea. You do need to find out where the water you pump out is allowed to be sent.
I suggest you read ABC's of Pool Water Chemistry.

Thanks so much. I did the dilute method for the test. I have read the ABC’s and have learned so much. We have a place in front of house that is plumbed into the pool so when we backwash I see the water flowing from that pipe which I think goes to sewer. We have a little creek ditch behind our house. The neighborhood was built up from flood plain I think. i Was hoping we could do something with a valve and adding water at the same time. Or do several drain and fill cycles

 

[mknauss]

The water exchange process works much better for saltwater pools or those that have significant temperature differences between fill and pool water.

You can rent a high power sump pump from Home Depot that would draw down half your pool volume in about 3 hours. Then refill and see where you are. If necessary, do it again. Or you can buy a sump pump but it will take a day or so to lower half way. Then you have to be concerned with leaving your plaster to dry out in the summer sun.

 

[Julie8000]

Thanks. I was going to buy a pump as can get it via Amazon and reduce going back and forth to Home Depot on a rental. If I do the smaller drain and fills my pool gets no sun in the late afternoon. If I drained once the sun is off pool and then fill after which could go on thru the night would that work? And to be sure, once I get the cya to the correct level, then do the slam, but don’t worry about mother chemicalsmtill then or should I start putting liquid chlorine after first drain and fill? Appreciate all the help. I know it will be worth it

 

[mknauss]

If you get a sump pump off Amazon, get a 1/2 hp one. You need a backwash hose or other larger hose or you will not move all that much water in the time you state. If you only remove 10% or so of the water each time it will take a very large amount of water to get your CYA to 50 ppm or so.

Add liquid chlorine, say 5 ppm FC worth each day during the process.

 

[Julie8000]

Thanks. I ordered the pump and the hose per your suggestion. Hope all goes well.