New user from Houston

[Leslie1]

Hello, everyone,
My name is Leslie. I purchased my place with an existing in-ground pool 3 years ago. Up until now, I have not attempted to learn much about how pool water works, but my pool service doesn't seem to be keeping the pool as clean as I would hope, so I am trying to learn. I think my pool is around 18,000 gallons, but I'm not really sure how to calculate that because the pool is a wavy custom shape (not kidney). The pool circumference is 92 ft and area is 550 sq ft, according to the contract the previous owners signed when they had the pool built. Depth varies from 3.5 to 5 to 4.5 ft.

I have a Nature2 trichlor dispenser, with the mineral cartridge. I haven't replaced the mineral cartridge since the first year of ownership, and I was just reading today that it's bad to do so, anyway. So I'll leave that alone unless an expert really thinks I need to break those metal balls out of the cartridge and throw them away?

Currently my CYA is off the charts above 100. When I diluted the pool water 50% with tap water and retested, I got 60. So I assume I need to empty the pool about half and refill. I read that if the water table is high, draining the pool is a risk. It has been a fairly wet year here in Houston. Can someone advise me if I can drain the pool halfway and refill now, or should I wait?

My current issue is yellow/green stuff growing on the tile grout below the water line. Other than that, the water looks pretty good.

Thanks for all you do!

Oh, and I have calcium? staining on the tiles at the waterline, but that has been there since I purchased the place.

Current test results:
FC: 10
CC:1
CH: 375 ppm
TA: 70
CL: turns orange instead of any of the yellow shades?
pH: 7.5
CYA: much more than 100, when diluted 50/50 with tap water, tests at 60

 

[bgollmer]

The only way to lower CYA and allow sane levels of FC to work properly, you will need to replace some of the water and stop adding stabilizer or chlorine tablets that also add stabilizer.
Rather than draining your pool partially, you can consider a no drain water exchange, documented here:
Draining

 

[Parac]

Assuming you have plaster, you don't want to drain and expose the plaster in this heat. The No drain exchange mentioned above is your best bet. 60 CYA with diluted sample puts you at 120 so yeah, replacing half is about right.

The test results look like they could be from a recommended test kit which is good, but can you confirm which test kit you have to make sure we are on the same page. Also fill out your signature so you don't get asked repeat questions about your setup as advice does vary some depending on your exact pool and equipment. Directions here: Signature further reading

You are correct in that you don't want to replace the mineral cartridge. Assuming it is old, it is probably empty and doesn't hurt much to leave that in place. The trichlor is why your CYA is so high. You should just switch to liquid chlorine for now and a lot of people here prefer a Saltwater Chlorine Generator (SWG) which has an upfront cost but makes pool care much easier.

General information: Pool Care Basics
App to track your numbers: PoolMath
Necessary chlorine level depends on your CYA value: FC/CYA Levels
Probably need a SLAM Process with visible algae
What your pool can look like if you follow TFP methods: How Clear is TFP Clear?