CYA Drain & Refill Guidance

sugast

Well-known member
Nov 21, 2018
49
Dallas, TX
Using a TF-100, I get the following results: FAC 9.5, CH 325, TA 100, CYA 150, PH 7.5. Obviously, my CYA is really high. I used the pool math calculator and it said i should drain 75% and refill to bring CYA down to 40. My pool is 22K gallons and I live in Dallas, TX.

Questions:
  1. Does draining the pool to such a low level pose any structural risk to the pool?
  2. Any tricks to gauge how much water has drained on a pool with varying depth levels?
  3. While the water level is so low, should i perform any maintenance? ie scrub the walls, etc.
  4. Is it safe to use the chlorinated water from the pool to water the lawn and trees?
  5. Is it safe to completely drain the spa? I have a spaSpa.jpg-spillover setup.
If there's anything else I'm missing, please let me know. I plan to tackle this effort over the next few days!
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
44,339
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Does draining the pool to such a low level pose any structural risk to the pool?
Potentially. You can do an Exchange - read Draining - Further Reading
Any tricks to gauge how much water has drained on a pool with varying depth levels?
You should use a sump pump. If you exchange, it is a fairly slow process and you can gauge your effluent by timing how long it takes to fill a 5 gallon bucket.
If you drain, it is best to get a sump pump from Home Depot or other rental place. Then just drain pretty much the entire the pool volume.
While the water level is so low, should i perform any maintenance? ie scrub the walls, etc.
Unless you have water line scale you want to bead blast, nothing to do with it empty.
Is it safe to use the chlorinated water from the pool to water the lawn and trees?
Might not be a good idea. Your pool water will have a significant amount of salt in it. Small amounts as long as you get lots of rain or fresh water watering later should not hurt.
Is it safe to completely drain the spa? I have a spa
Yes
 

HermanTX

Gold Supporter
May 20, 2020
2,640
Katy TX
Pool Size
14600
Surface
Plaster
Chlorine
Liquid Chlorine
How far you can drain is really dependent on your water table level. So you need to be cautious but 25% of pool water seems good but you may want to talk to any neighbors that have pools to determine if they had any issues.

I calculated my depth per inch (rough estimate) using my surface area of pool. So I would then estimate that my first step (at 6 inch water depth) was x gallons, my second step at 18inches water depth was x gallons. Obviously every pool is shaped differently and how it slopes all affect calculation but at least you are relatively close. So lets say you drain to bottom of your bottom step. When you start to refill, take a picture of your water meter reading as the starting point. Then when you reach the top of the bottom step take another reading of your water meter and so on. This way you will know at the end what you removed/added and also for the future you can then have a better calculation what volume is at each depth of your steps

I removed all my return eye outlets in both pool and drain - removed any debris or build up and set up to properly direct flow. You be amazed how people may play with these things and they get all pointed differently.

Chlorine water is not good for grass or plants - suggest you drain to street or to some type of drain

Depending on how your plumbing is setup, you may drain the spa with the pool. I have drained my spa separately using the bottom spa drain to remove all water. You can calculate the volume of your spa much easier - just use 2 rectangles (one with max depth in middle) and other with depth of seat.

You may want to look at your water bill. If your water usage also affects the fees for garbage services or drainage fees, then call the water company to tell them you are filling a pool so you do not get those extra fees on your pool volume.

Good Luck. Have you tested your fill water so you know what you are filling it with?
 

sugast

Well-known member
Nov 21, 2018
49
Dallas, TX
Great tips as always! I haven't tested my fill water but I will this evening. As you can see from the picture below, my pool has a drain pipe that goes directly to a sewer line. Do I still need to rent a pump or should I usethe backwash valve on my filter to direct the water to the sewer?

IMG_8712.jpg
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
44,339
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Do I still need to rent a pump or should I usethe backwash valve on my filter to direct the water to the sewer?
I doubt your hose will keep up with the pool pump. And you do not want the pool pump to inadvertently run dry as it will be destroyed.

Are you going to exchange or drain? Did you read the Draining article?
 

sugast

Well-known member
Nov 21, 2018
49
Dallas, TX
Merged threads - TFP Mod
I have a couple of issues and I'm not certain how I should go about fixing them. I'm fighting yellow algae and my CYA is 140. I know I have to drain and refill the pool to get the CYA down. I wont be able to get to it until Saturday. I have my chlorinator on the highest setting and I've shocked the pool and the FAC only reached 5. It was down to 0 before I shocked. My fear is the algae will be out fo control by the weekend. It's already pervasive.

My pool guy told me to turn off the pump, let the water settle for 8 hours, place the submersible pump on the first step and drain to first step. Then refill. Place pump on second step, drain and refill. He claims the CYA will rise to the top of the pool and I can lower the CYA without having to drain as much water. Is that true or should I just place the pump on the bottom and drain 2/3 of the water and refill? Any reccomendations on a path forward would be appreciated. Thanks

The current test results:
FAC 5
PH 6.9
TA 16
CH 258
CYA 140
Phosphates 3987
TDS 600
 
Last edited by a moderator:

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
18,596
Tucson, AZ
Pool Size
16000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Your pool guy is completely wrong. CYA does not “rise to the top” … that’s just nonsense.

If you need to do a significant drain, and you absolutely do need to do one if you ever hope to get your algae under control, then you need to do an exchange drain where you fill fresh water into the pool while draining pool water out. Where you place the fill hose and submersible pump matters. It’s explained in this wiki -


Also, you need to get rid of the pool guy and take of the pool yourself. Are you using a recommended test kit to get those numbers or is that pool store testing. You need your own test kit and you must do your own water testing if you hope to get this situation under control.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
29,063
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
He claims the CYA will rise to the top of the pool and I can lower the CYA without having to drain as much water. Is that true

That is not true, to say things politely.

or should I just place the pump on the bottom and drain 2/3 of the water and refill?

Yes.


What test kit are you using?

Where did those test results come from?

Are you confident your CYA is really 140?
 

Donldson

TFP Expert
LifeTime Supporter
Jun 12, 2009
5,150
NW Ohio
Any reccomendations on a path forward would be appreciated.
Not allowing someone who openly demonstrates this level of ignorance of pool chemistry to care for your pool would be the biggest recommendation I could give.

This is like the 4th time you've had CYA problems, twice this year. It's not going to get better by continuing to do things the way you've been doing them.
 

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Lilypad

Silver Supporter
Bronze Supporter
Nov 12, 2016
373
Plano, Texas
You’re using your chlorinator "on the highest setting" with tabs that add CYA.
Using a "shock" product that most likely adds CYA.
There is so much CYA in the water that the chlorine cannot be effective.
You’re going to be up against constant algae, regular drain/refills and expense to manage it this way.
Your pool guy does not know what he is doing.

If you take the advice given here, and act upon it....take control of your pool....you will be surprised
how simple it is and how much money you can save.
 

sugast

Well-known member
Nov 21, 2018
49
Dallas, TX
Not allowing someone who openly demonstrates this level of ignorance of pool chemistry to care for your pool would be the biggest recommendation I could give.

This is like the 4th time you've had CYA problems, twice this year. It's not going to get better by continuing to do things the way you've been doing them.
thanks for the guidance team. I use the TF Test kit. I took it to Leslie's to get a second measure on my CYA. My local store uses the automated test. My test and their test were really close. Even the guy in the store admitted its not more accurate than the Taylor kits but it's more consistent. I teased him that consistently inaccurate is not too helpful!
 
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