Replaced half the water in my pool... What now?

RoberTX

Well-known member
Jun 18, 2010
55
Arlington, TX
When I drained the pool down, the water seemed much cloudier, cloudier than I think can be attributed to removal of the water... I left the filter running through most of the drain/refill (diverter valve set to DRAIN only - no SKIM). Right after refilling, when I brushed the walls/floor, white 'dusty' clouds appeared... never seen this before. Maybe b/c my pool water is normally polished by the DE filter, and this water straight from the city is not as clean? Anyway, after running the filter for another 3 hours this morning, the cloudiness while brushing is practically gone. The overall water clarity is slightly worse than before, but I expect the filter to catch up by the end of the day.

Here are the test results after the refill, hot off the press:

FC 1
CC 0
pH 7.8
TA 110
CH 220
CYA 50

So, my question is what should I bring the FC up to? Pool Calculator says that I can add 280 oz. of 6% bleach to bring my FC up to 6 (target according to the TFP Chlorine/CYA Chart). Any need to bring it higher than that as there was some algae present prior to the refill? I've it off the walls, maybe the minor cloudiness is from algae?

I think I might add some muriatic acid as well to get the pH to 7.5 or so.

Please advise on what I should do, and how to do it.

Probably not helpful, but here are the test results from my tap water:

FC 0.5
CC 3.5
pH 8.0
TA 110
CH 120
CYA 0 (waste of regents, wasn't thinking :roll: at least my gf got to see how it works! :) )

By the way, this is kind of a continuation from another post, found URL here. I figured I might as well have a fresh new thread for a fresh new start!

Thanks,
Robert
 

duraleigh

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Even with just that little bit of residual cloudiness, I think I would go ahead and shock it just to be safe. Bama is probably correct that you do not need to but Shocking will get you off to a flying start. (BTW, nice work on getting your CYA down.)

Lower your pH first, then I would suggest shocking the pool exactly as prescribed in Pool School.
 

RoberTX

Well-known member
Jun 18, 2010
55
Arlington, TX
I went ahead and added 2 1.42 gallon jugs (364 oz) of 6% bleach. Pool Calc says that should get me to an FC of about 7. How long should I wait before testing it again? I know I read on here somewhere, but can't find it now! What difference does the order in which one adjusts pH and chlorine make?

Thanks again to everyone here at TFP. Everyone has bee very helpful!

:cheers:

Robert
 

duraleigh

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Lower you pH first. Higher than 10 FC levels makes the pH test invalid.

7ppm is not bad for FC but 15ppm held there until that cloudiness is completely gone is better! :wink:
 

RoberTX

Well-known member
Jun 18, 2010
55
Arlington, TX
This morning at 8:00 AM my FC was at 6 (target for CYA 50).

At 7:00 PM it had dropped to FC 3 (minimum is 4 for CYA 50) with only a small trace of CC (very light pink disappeared with one drop of R-0871). It was very sunny and hot today (100 F high) but the water still looks great.

Does this drop of FC by 3 ppm seem reasonable? The minimum is 4, so should I target a higher FC for now?

I went ahead and targeted an FC of 7 for now (added 224 oz of 6% bleach, per pool calc).

pH 7.5
TA 110
CH 220
CYA 50

Robert
 

loughps

Well-known member
Apr 26, 2009
221
Northeast Ohio
A 3ppm loss on a sunny day is pretty normal. If you're not going to shock, I'd target a little higher nightly FC (8 or 9), so that by the next evening it's still above 4. You never want it to go below 4 even for a little while, adjusting your nightly dose should help with that.
 

RoberTX

Well-known member
Jun 18, 2010
55
Arlington, TX
Definitely no need to shock... I think I was just taking the Chlorine / CYA Chart a little to literally :p It suggests a Target of 6, but maybe correcting to 8 or 9 seems reasonable in anticipation of many hot sunny days to come. If I target 8..9, that should keep me away from my minimum of 4 .

Any thoughts?

BTW when I add the chlorine, I pour it slowly in front a return jet at the deep end, and then leave the pump on for about 30 minutes, is that adequate?

Thanks,
Robert
 

loughps

Well-known member
Apr 26, 2009
221
Northeast Ohio
Sounds good with the exception that I'd probably run the pump for at least an hour. I tried searching other posts to see what others recommend, but didn't come up with anything concrete enough to point to other than some suggestions for running one to three hours after adding chemicals in the evening.

My two cents is, run it for at least an hour if you can. See where 7 ppm from tonight leaves you tomorrow evening, if it's not above 4, go to 8 or 9 until you find what works for you.
 

RoberTX

Well-known member
Jun 18, 2010
55
Arlington, TX
That sounds very reasonable.

Right now my pump timer is set from 6 am to 6 pm, but now that I will be adding the bleach around 7pm to 9pm every night, I'm thinking of changing it to something like 10am to 10pm...

Robert
 

Butterfly

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May 30, 2007
10,045
South Carolina
As loughps said, running the pump at least an hour after adding chems is a good idea, in fact it is recommended. :wink:

Lots of us jug dumpers add our nightly dose and then turn the pump off after an hour.

Sometimes I will shorten the one hour run time after dosing if I am in a particular hurry; but, I will help mix the chlorine/bleach by using a brush or water hose to help stir the water and mix.
 

RoberTX

Well-known member
Jun 18, 2010
55
Arlington, TX
Thanks for the tips.

For anyone else asking the same newbie questions as me, I found some helpful advice from the Pool Calculator Basic Chemistry page

The target FC level is a minimum. You always want the FC level to be at least as high as the target level. FC is commonly lowest in the evening after sunlight has been reducing it all day. If you are adding chlorine once a day in the evening you need to bring the chlorine up to a higher number than this so that your FC level the next evening is at least the target level. How much higher depends on your CYA level, the amount of sunlight that falls on the pool, and how much the pool is used. A CYA of 30 to 50 will generally lose between one half and two thirds of the FC over the course of a sunny day.
Based on that, I will add enough bleach to bring my FC level up to Target + 'anticipated chlorine loss over the next 24 hours'. For me this will be 6 + 3 = 9.

That way my chlorine level should cycle between 6 and 9 every day. :goodjob:

Robert
 

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