Water Exchange - Correcting/Maintaining During Process?

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FergieWheeler

FergieWheeler

Member
Jul 22, 2019
10
Paris, Ky
My test kit arrived this morning, and I tested the water. I already knew my CYA would be high, and given I dumped in two gallons of Pool Essentials chlorinating liquid (10%) last night, I knew I'd have some free chlorine showing up for a change. Here are my stats:

FC - 2.6
CC - 0.4
CH - 280
TA - 190 (includes subtraction for high CYA)
PH - 7.4
CYA - 200
Copper - 3 ppm according to AquaChek Copper test strips

First of all, the pool store's magic copper remedy (Pool Magnet Plus and Sparkle Up) did not work. I'm sure they would have loaded me with down another $250+ bill had I returned for re-testing this week as recommended.

Background: Our pool has an older vinyl liner (7 years) in 34-year old coping. We have three areas along the coping where the liner is pulling away. Each area is about 10 inches to 12 inches long. It was much worse last year, but we managed to push most areas back into the coping and apply liner lock. Still, these three problem areas persist, and I don't want them to get worse or have new areas crop up.

I know completely draining and refilling the pool is the ideal answer, but with the fragility of the liner and coping, I'm more inclined to exchange water with a pump in the shallow end and a hose filling in the bottom of the deep end (the water is super warm so I'm thinking that arrangement would work best with the cold water from the hose). I know this process might take forever to get the CYA down and won't fully eliminate the copper, but I'm thinking it will be the least burdensome on the liner.

Have people had success using this method? What should I do regarding maintenance chemicals during the process? Daily testing? Chlorine nightly? I tested our tap water, and the PH is ideal and so is the TA.
 
You are correct that the cold water goes in the bottom of the deep end and you remove warm water from the shallow end. Assuming you have stairs on the shallow end put the pump just deep enough to reliably pull water. Cold water sinks, warm water rises.

Treat the water the way you always do to maintain your FC and PH. Can't help you with the metals. I've never had that problem.
 
Many folks have used the water exchange method. @mknauss is our expert on that process.
 
You can exchange some water without draining.

If you place a low volume sub pump in the deep end and pull water from there while adding water in the shallow end (through a skimmer or into a bucket on a step so you lessen the water disturbance) you can do a fairly efficient exchange. That is assuming the water you are filling with is the same temperature or warmer than your pool water. If your fill water is much cooler than your pool water, then switch it. Add the water to the deep end (hose on bottom) and pull water from the top step.

The location of the pump and fill hose may change if you have salt water, high calcium, etc.
In my pool, with saltwater and high calcium when I drain, I put the pump in the deep end and hose in shallow end. The water in the pool weighs more per unit volume than the fill water from the hose.

Be sure to balance the water out and water in so the pool level stays the same. Also be sure your pool pump is disabled during this process. Once started do not stop until you have exchanged the amount of water you wish.
 
Depending on where and what size hose you use for the effluent from the pump, you will get 7-10 gpm. So for your pool, for a complete exchange, will take a couple days. You can add some liquid chlorine if you like during the exchange. Once you have run the process, circulate and brush the pool really well before taking a sample for your new base line water chemistry.
 
I just wanted to give a quick update. I allowed the water exchange to go through most of the weekend. I am pleased that copper is no longer showing on the test strips, and I lucked out on reducing CYA to a level that is acceptable. Here are the numbers:

FC - .2
CC - .2
CH - 210
TA - 184 (includes subtraction for CYA)
PH - 7.4
CYA - 50 (yay!!!)
Copper - 0 ppm according to AquaChek Copper test strips

I will be adding 210oz of 10% liquid chlorine tonight along with 76oz of dry acid (muriatic acid gives me the willies...I know it is the better choice, but I'd rather deal with something less caustic). Currently, my goal is to reduce ph to 7.2 to reduce TA and aerate to increase PH. Should I reduce ph to 7.0, or will 7.2 be enough to lower TA? Am I on the right path?
 

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