Increasing CYA

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PoolStored said:
You need to water exchange at least 65% of your pool water.
The only other option is to hire a reverse osmosis company...I don't think they are cheap. This one is in San Diego County. California Pool Co. | Reverse Osmosis Pool Filtration in California

Read "no drain water exchange" here:

Draining - Further Reading

www.troublefreepool.com www.troublefreepool.com
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Ugh. That looks like a nightmare.

So, rather than simply exchanging 65% of the water (calculating the speed as best as I can), can't I just re-test the water from time to time and see if the CYA levels are reduced?
 
pablocruz23 said:
So, rather than simply exchanging 65% of the water (calculating the speed as best as I can), can't I just re-test the water from time to time and see if the CYA levels are reduced?
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Two issues:
1) CYA degrades about 5-10ppm per MONTH. Would take at a minimum a year.
2) At that CYA level, you cannot maintain enough FC in the pool to sanitize. It isn't safe.
 
Sorry, I wasn't clear.

If I do the no drain water exchange (I have a pump), then I'll put the pump in the deep end and fill at the skimmer. However, rather than wait for 65% of 20,000 gallons to be exchanged, what if I test the CYA from time to time as the exchange is happening? It might take as much water as you think. Possible?
 
pablocruz23 said:
Possible?
Click to expand...
Nope.
  1. You need to turn the pool pump off when you do the exchange. You need to do the calculation to determine where to pump and where to add. If you don't have TDS, use 1000 for PWTDS and 500 for FWTDS. We want the water to stratify so that you are not pumping out the fill water.
  2. Because the water is stratified, you won't be able to test the actual CYA during the exchange.
  3. CYA is a straight 1:1. 65% reduction in water is removing 65% of the CYA, so your net result would be a CYA of 63. You need to replace at least 65%. It may take more if you get any mixing, and a better end target would be 50CYA, so you may need to do 75%
  4. You will need to run the pump for 24 hours after the exchange to allow it to mix before you retest.

A good rule of thumb is that a garden hose is 5GPM. You can time/test with a 5 gallon pail...time how long to fill.
A pro tip on the garden hose on the sump pump, is to see if you can get it to closely match the pool input. If you have 5GPM in, you want 5GPM out. If the pump is going to fast, put the hose over something tall (like a ladder)...this adds head to the pump and slows down the flow. I got mine close enough I could go to bed and not worry.

If you need to exchange 15K gallons / 5 GPM = 3000 minutes / 60 min/hour = 50 hours. I think mine took 43 hours, but I ran two hoses (30K pool).

Sorry to be the red pill.
 
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Its always wise to over drain/exchange. If you fall short, you'll lose a chunk of new water to lower the remaining CYA.
 
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PoolStored said:
Nope.
  1. You need to turn the pool pump off when you do the exchange. You need to do the calculation to determine where to pump and where to add. If you don't have TDS, use 1000 for PWTDS and 500 for FWTDS. We want the water to stratify so that you are not pumping out the fill water.
  2. Because the water is stratified, you won't be able to test the actual CYA during the exchange.
  3. CYA is a straight 1:1. 65% reduction in water is removing 65% of the CYA, so your net result would be a CYA of 63. You need to replace at least 65%. It may take more if you get any mixing, and a better end target would be 50CYA, so you may need to do 75%
  4. You will need to run the pump for 24 hours after the exchange to allow it to mix before you retest.

A good rule of thumb is that a garden hose is 5GPM. You can time/test with a 5 gallon pail...time how long to fill.
A pro tip on the garden hose on the sump pump, is to see if you can get it to closely match the pool input. If you have 5GPM in, you want 5GPM out. If the pump is going to fast, put the hose over something tall (like a ladder)...this adds head to the pump and slows down the flow. I got mine close enough I could go to bed and not worry.

If you need to exchange 15K gallons / 5 GPM = 3000 minutes / 60 min/hour = 50 hours. I think mine took 43 hours, but I ran two hoses (30K pool).

Sorry to be the red pill.
Click to expand...

Thank you for explaining all that. I'll figure out the TDS/PWTDS. The water temperatures are pretty close, less than 20 deg different.
 
DeltaT = (PWT - (PWTDS / 165)) - (FWT - (FWTDS / 165))

Assume your Pool water is 75 and fill is 60, 15 degrees. Normal TDS difference...
15 degrees is significant...PWT / FWT differential is going to be the biggest factor.

DeltaT = (75- (1000/165)) - (60 - (500/165))
DeltaT = 69 - 57 = 12.

Fill at the deep end and pump from the top....
 
pablocruz23 said:
Thank you for explaining all that. I'll figure out the TDS/PWTDS. The water temperatures are pretty close, less than 20 deg different.
Click to expand...
If your goal is to drain the least amount of water than draining it once and then refilling once is the most efficient. There will always be mixing with the other process.
 
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