Attempting my first water exchange

jasonburks

New member
Aug 19, 2019
3
Austin, TX
Hello,

I've got some of my pool stats creeping up and it seems that I need to get about 35% or so of my water exchanged. It seems it's best to do an exchange vs a drainage/fill. So I have a question on procedure. Typically I'm reading if you are using city water that comes out colder than pool which is basically any water here in Texas then put the fresh water hose at the bottom of the pool and drain from the top-ish if using a sump. I currently don't have a sump but could get one if needed. When I first had a service guy out he said I could drain water from this water spout installed inline with the pool equipment (see photo). I didn't ask much more questions wise since I wasn't doing any of this back then. My guess is if I'm putting fresh water in at the same rate, it shouldn't drop below the skimmer so I could run the equipment as normal, the spout is after the pump & filter, so can I just run a hose from that to the street and drain, and run a hose from the house to fill and just keep testing until my CYA & CH come back down? Last full reading using TF-100.

Latest Readings:
Water Temperature: 89
Chlorine:
  • FC: 1.0
  • CC: 0.5
  • TC: 1.5 (added a jug of liquid chlorine this morning to raise this)
PH: 7.8 (Added acid this morning to drop this)
Total Alkalinity Test: 150
Calcium Hardness Test: 400
CYA Test: 70
CSI: 0.60

Pool Stuff:
17K gal Pool/Spa, IG plaster, 2 HP VSP pump, 525 sqft cartridge filter, Pentair 320 In-line Chlorine Tablet Feeder, Delta UV Filter, Hayward Heater, 2HP Spa Bower, Hayward SharkVac cleaning robot, TF-100 Test Kit

IMG_1087.jpg
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,749
Northern NJ
Welcome to TFP.

Your pool pump is very strong and will push water out at a greater rate then your hose can fill the pool. It is critical to get the in and out water to balance for the water exchange to work. Buy a submersible sump pump that will pump out of a garden hose around the volume that your hose will fill the pool.

You also don't want to risk your main pool pump running dry and getting damaged if the skimmer runs low on water.
 

jasonburks

New member
Aug 19, 2019
3
Austin, TX
I also ran a new test to see where things are, below are the results. The Calcium Hardness and CYA levels are the ones concerning me the most.

Water Temperature: 88

Chlorine Drop Test
  • FC: 5.5
  • CC: 0.5
  • TC: 6.0
PH: 7.5

Calcium Hardness Test: 425
Total Alkalinity Test: 130
CYA Test: 70
CSI: 0.26
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,749
Northern NJ
CH of 425 is not a problem.

CYA of 70 is on the high end for a chlorine pool. But you will get natural CYA degradation and your CYA will be down in a few months.

Lower your TA to 60-70 and you will bring your CSI down to healthy range below 0.


I don't see a need for you to drain water now.
 

jasonburks

New member
Aug 19, 2019
3
Austin, TX
So looks like use muratic acid to get PH down to 7.0-7.2 then use aeration to raise PH without raising TA.

I don't have SWG, but I do have a spa. Can I just run the spa jets to do this? Any feel for how long I should let them run, we talking a couple of hours, days?

Also is 7.0 unsafe for people to be in the pool? Just helps me understand when I'm going to do this.

Last question, on the Calcium Hardness test, sometimes I feel like I'm cheating, so I fill it up and I start to lose visibility of the dot (this is north of 70), but if I squint pretty good I can still make out some black so I keep going until it's unrecognizable which gets me around 70. Am I just fooling myself about it being 70 or am I doing it right?
 

usedtobeayooper

Active member
Aug 20, 2019
27
Hamilton, MI
Last question, on the Calcium Hardness test, sometimes I feel like I'm cheating, so I fill it up and I start to lose visibility of the dot (this is north of 70), but if I squint pretty good I can still make out some black so I keep going until it's unrecognizable which gets me around 70. Am I just fooling myself about it being 70 or am I doing it right?
Interested to hear the Pro answers to this, too. I've been told over and over in various scenarios when talking to people "no sign of the dot, no black"... so I find myself doing the same. Under my bright lights in the garage, or outside daylight, back to the sun, regardless of scenario, I seem to do the same thing....

Correction: I read your post again, I was referring to CYA, not hardness.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,749
Northern NJ
So looks like use muratic acid to get PH down to 7.0-7.2 then use aeration to raise PH without raising TA.

I don't have SWG, but I do have a spa. Can I just run the spa jets to do this? Any feel for how long I should let them run, we talking a couple of hours, days?
Running the spa jets will raise the pH of the spa water but have little effect on the larger pool water.

How long depends on how vigorous your aeration is. People rig up different things. Some type of spray fountain connected to returns. Does your spa have a waterfall? Turn it on. A submersible pump bubbling in the pool.

Also is 7.0 unsafe for people to be in the pool? Just helps me understand when I'm going to do this.
7.0 is safe to swim in. Target 7.2-7.4. If you accidentally get to 7.0 its ok. The sweet spot for lowering TA is run it in the range of 7.2 to 7.6. Repeat that range as often as you can.

Last question, on the Calcium Hardness test, sometimes I feel like I'm cheating, so I fill it up and I start to lose visibility of the dot (this is north of 70), but if I squint pretty good I can still make out some black so I keep going until it's unrecognizable which gets me around 70. Am I just fooling myself about it being 70 or am I doing it right?
Don’t obsess over the CYA test. +/- 10 is fine. We round up. If the dot disappears between 70 and 60 you call it 70. If between 80 and 70 you call it 80.