Need to drain pool

[Johnblackthorne]

Just bought a house with ~18k gal pool and spa. Water looks crystal clear but when I tested it FC, TA, and CYA were super high. Didn’t test CH. These were my results with TF-100.
FC: 17
CC: 0
PH: 7.5
TA: 17
CYA: Wayyyyyy over 100

I spoke to the service that had been maintaining it and he told me alkalinity, cya (140), and total dissolved solids were all high, but told me I’m doing the chlorine test wrong and they keep it at 3-5 ppm. I did the color match test and chlorine was bright orange, and then FAS-DPD and used 44 drops last night and 34 this afternoon.

First question, am I doing the chlorine test wrong? I read all the instructions closely but feel like I must be doing something dumb to be so off. Second question, drain the whole pool or just 2/3rd as the service recommended? Any tips for starting from scratch with new water? I read most of pool school but my head is spinning.

Apparently the pool was in bad shape all winter and owner refused to drain, and now they’re using a lot of chemicals just to make it look clear. Appreciate any help!

 

[Rancho Cost-a-Lotta]

Welcome to TFP. Don't worry, we are here to help.

Sounds like your test methods are accurate. Realistically, FC of 17 ppm is probably what you need with your CYA level FC/CYA Levels. Let's find out for sure. Follow Step 8 in the instructions below. You will be diluting your pool sample to achieve a more accurate CYA level. Also test your CH using a 10 mL sample.

CYA - Cyanuric Acid Test

Cyanuric Acid (CYA) is the chemical name for what is commonly referred to as Stabilizer … Read more…

www.troublefreepool.com

 

[Jimrahbe]

John,

I'd drain the whole thing and start over fresh...

Thanks,

Jim R.

 

[Johnblackthorne]

Thanks for the help! I was able to get back to the house today and test, CYA was 200 using the method of diluting with tap water. It is probably slightly higher as it was still just short of the 100 mark on the viewing cylinder. CH is 1,175.

I found this post on draining: Draining - Further Reading

and I’m thinking of doing the method of draining and adding water simultaneously. I haven’t tested the tap water, but I’m imagining a large delta in TDS. Any recommendations on what percentage water to replace? Pool math told me 69% when I plugged in the CH level. I’m ok with doing any amount, and I’d rather start from a good point than save a few bucks on water. Also, once I have exchanged the water is there any protocol on which order to address chemistry? My gut says get chlorine right first, but I could have easily missed a post about how to start fresh.

Thanks again!