Drain and Refill to Correct CYA

[WalterE]

Following instructions from this forum, I have done a 1/2 drain and refill with city water. Would like some guidance as to what to do next in migration to BBB.
Prior to Drain.. Pool was clear, but previously I had a couple of algae attacks and was using pool store advice with pucks and shock, with limited success and very high CYA. Ordered Taylor k-2006 and here are numbers prior to drain.
----------------------------------------------------------------
FC 2.0
CC 0.5
PH 7.4
TA 150
CH 70
CYA well over 100 (note: on Taylor it's half way between the 100 mark and the bottom of the tube)
------------------------------------------------------------------------
Just for info, I measured the city tap water prior to the refill.
------------------------------------------------------
FC 1.6
PH 7.3
TA 20
CH 30
CYA 0
-----------------------------------------------------
Now here are my numbers after the drain and re-fill
----------------------------------------------
FC 1.0 right after refill
FC 5.0 after 2 gallons of bleach
CC 0.4
PH 7.6
TA 80
CH 50
CYA greater than 100 estimating 130
----------------------------------------------------
Looks like several more half drains and refills to get CYA where it needs to be
Would like some direction and help to ensure a smooth transition to keep me out of trouble.

 

[JVTrain]

Based on your TA and CH levels after the fill, you are getting very close to a half drain. I would do one more half drain and you should be close to 60-70 ppm CYA. One more would likely get it low enough for normal maintenance near recommended levels.

After you've done one more, post results and we'll go from there. Read up in Pool School, specifically the CYA/Chlorine chart and other articles such as Recommended Chemicals, Recommended Levels, How to Chlorinate your pool, etc.

 

[poolnoob.ca]

Hi WalterE, your reading of 0.4CC indicates you are using 25ml of water sample to test. If you only use 10ml water, you can save your testing reagents. Each drop would then equal 0.5ppm chlorine instead of 0.2ppm. The 0.5ppm precision is normally adequate.

p.s. it looks like you have a great grasp of what you're doing so far!

 

[WalterE]

According to the FreeChlorine/CYA chart, at a CYA of 100, I should have FC 7 minimum, 12 Target and 39 for SLAM. According to the PoolMath chart, to get to 12 from 5 would require 3 gallons, which would not be too bad, but to slam, would require 16 gallons. That makes me nervous. Would that damage my pool?

100*​

7​

12​

39​

 

[pooldv]

No, it would not damage your pool, it is just a lot of bleach/chlorine to buy, haul and add. I had to slam earlier this summer with CYA at 70 and FC in the upper 20s with no issues. We swam the whole time. Our CYA is 70 because we have saltwater.

 

[DaninFLA]

According to the FreeChlorine/CYA chart, at a CYA of 100, I should have FC 7 minimum, 12 Target and 39 for SLAM. According to the PoolMath chart, to get to 12 from 5 would require 3 gallons, which would not be too bad, but to slam, would require 16 gallons. That makes me nervous. Would that damage my pool?

100*​

7​

12​

39​

you are correct about your concerns about SLAMing levels. but you also do not have a CYA of 100, it is 100+. it could be 110, it could be 150. you need to do another drain until the CYA test is within range...i.e. less than 100. you are doing a lot of work to fix your pool, so don't stop when you have done 75% of the work. one more 50% drain should do it.

another concern with having your CYA that high is the FC levels you maintain. remember that the pH test is invalid if your FC is about 10ppm. so if you are above that during regular loading you cant test and adjust pH. water is pretty cheap and you will save money in the long run by doing another drain and getting your CYA levels down. just chalk it up as punishment for following pool store recommendations now that you are on the TFP methods, you shouldn't have to worry about it again ever.

and to answer your question, no, you will not bleach your liner. the whole CYA/FC relationship is based on oxidizing power of the free chlorine. that's why it goes up as CYA goes, up. a pool chlorinated at the target FC for CYA of 20 is the same as CYA of 100. in fact, even though you would be at FC of 12ppm with CYA of 100, its not as harsh as a pool with 0 CYA and 1ppm of FC, like a public pool. no worries at all

 

[WalterE]

Following instructions from this forum, I have done two 1/2 drains and refill with city water. Would like some guidance as to what to do next in migration to BBB. I have locked up the pucks and the bags of shock and so far only putting gallons of bleach in the pool. It is taking about 1 gallon per day to maintain FC of 5.
Prior to 1st Drain.. .
----------------------------------------------------------------
FC 2.0
CC 0.5
PH 7.4
TA 150
CH 70
CYA well over 100 (note: on Taylor it's half way between the 100 mark and the bottom of the tube)
-----------------------------------------------------
Now here are my numbers after the 1^st drain and re-fill
----------------------------------------------
FC 1.0 right after refill
FC 5.0 after 2 gallons of bleach
CC 0.4
PH 7.6
TA 80
CH 50
CYA greater than 100 estimating 130
---------------------------------------------
Now here are my numbers after the 2nd drain and re-fill
----------------------------------------------
FC 2.0 right after refill
FC 4.0 after 1 gallon of bleach
CC 0
PH 7.6
TA 50
CH 50
CYA 80 coming down, but not quite there
----------------------------------------------------
What to do next?. Can I live with this, maybe do another drain next spring? Any of the numbers bother you?
Thanks for all your help. I'm still learning as you can tell.

 

[Paul.]

Hey Walter great job on getting you CYA down to a more manageable level.
Are you seeing any algae. If not, I would stop draining and see if you can manage to the pool at that CYA level. Yes you will need a higher FC if you decide to SLAM but maintaining a proper FC in the balanced pool should be ok even at that CYA.

Keep in mind that your should Target an FC of 9 (for CYA of 80) and never allow it to go below 6 to prevent any algae growth.

Your TA and CH can be adjusted if needed.
Do you have a heater or any other products that may indicate a need to increase your CH, if not keep it like it is (considering the warranty conditions for your products).
I would see how stable my pH is at that TA and increase as needed.

 

[WalterE]

Thank you Paul, this helps a lot. No algae at this time. Pool is very clear. No heater.

Montreal is on my list as the next vacation. Looking forward to seeing your beautiful city for the first time. Thinking about the train trip over to Halifax.
wally

 

[DaninFLA]

great job Walter! if you are going to close the pool, I would just stop with the CYA reductions. you will have to drain water for winterizing which will lower it further and you can make any more small changes next year when you open it. you have definitely set yourself up for success for next year, nice work! now just make sure you close your pool per the TFP guidelines so you can open up to clear water next year and avoid delays. keep your pool running until the water temp is 60 degrees

 

[WalterE]

Thank you Danin. I don't close my pool for the winter. It is the highlight of the view from my house and I thought the cover distracted. What I'm thinking is to leave it like it is, keep the FC at 9 until next spring and practice TFP with BBB. At that time, do one more 1/2 drain and refill, which should take it to 40 for the swimming season

Will that work?

Also, What should I expect for the amount of Bleach to that will be required to maintain the target FC? I know it will vary depending on sunshine and other factors, but a ball park range. Especially over the winter where the usage should be significantly reduced.

Thanks again for your help.

 

[Cinic]

I've been managing the pool that came with our new house since July with a CYA of 80. In the worst part of the blaring AZ sunny days, I'd use a bit over a 1/2 gallon of 8.25% bleach to keep at or around the target of 9.

It's tapered off as the temperatures have come down and the sun is starting to lean over more. A gallon jug now lasts 3 to 4 days. I was planning on doing the drain & refill to get the CYA in the 40 range at the end of our season, but might just wait until the spring if the bleach demand keeps decreasing.

 

[DaninFLA]

Thank you Danin. I don't close my pool for the winter. It is the highlight of the view from my house and I thought the cover distracted. What I'm thinking is to leave it like it is, keep the FC at 9 until next spring and practice TFP with BBB. At that time, do one more 1/2 drain and refill, which should take it to 40 for the swimming season

Will that work?

Also, What should I expect for the amount of Bleach to that will be required to maintain the target FC? I know it will vary depending on sunshine and other factors, but a ball park range. Especially over the winter where the usage should be significantly reduced.

Thanks again for your help.

ok, gotcha Walter. in the winter with lower water temps your FC consumption is going to go down quite a bit. once you hit 60 degree water temp its going to go even lower. use pool math to determine the volume of bleach needed to replace 1ppm of FC, that's might be where you are going to end up at. during the peak of summer, probably 2-3ppm is typical.

if you are not going to close the pool, I would do another water change and get your CYA down to 60-ish and then you wont have to worry about it later. but where you are at is manageable