chlorine at night, need to drain pool?

[irvinenewbie]

I calculated it'll take 10hrs to drain 1/2 of 21K pool given pump flow rate of 1K/hr. When I checked at 4hr, 1/2 to 2/3 of the pool is drained already. So there is no 2 stage refilling. Either the pump flow rate is wrong or the pool volume is wrong. I tested 1 part residual pool water with 2 parts of tap. CH and CYA are in range. So hopefully everything will work out.

Is it ok to turn the water off at night before it's completely refilled? Will it promote algae growth since chlorine level is low? Keep in mind that there may be a nidus of algae growing. Can nylon brush be used to brush off algae or does it need to be wire brush?

 

[polyvue]

Is it ok to turn the water off at night before it's completely refilled? Will it promote algae growth since chlorine level is low? Keep in mind that there may be a nidus of algae growing. Can nylon brush be used to brush off algae or does it need to be wire brush?

One night with low water can't hurt anything... be sure any automatic pump timer is turned off so it doesn't start pumping before you can complete the refill. If it makes you feel better, add some liquid chlorine to the affected area but you must circulate it a bit so it doesn't puddle in one place (you could use the submersible pump for this by redirecting the outflow back into the same area.)

No opinion or experience regarding what type of brush to use. It's the chlorine that will kill the algae; brushing is mostly just clean-up work.

 

[irvinenewbie]

Thanks for your answer, polyvue! Really appreciate the fast response.

If it makes you feel better, add some liquid chlorine to the affected area but you must circulate it a bit so it doesn't puddle in one place.

I thought it needed a concentrated dose at the algae site for topical application. No? Since I don't have any test results before refill is completed, I don't know how much to add. I poured about a cup or two right on top of the water where presumed algae was. that was late afternoon. Do I need to mix it now?

 

[polyvue]

Thanks for your answer, polyvue! Really appreciate the fast response.

If it makes you feel better, add some liquid chlorine to the affected area but you must circulate it a bit so it doesn't puddle in one place.

I thought it needed a concentrated dose at the algae site for topical application. No? Since I don't have any test results before refill is completed, I don't know how much to add. I poured about a cup or two right on top of the water where presumed algae was. that was late afternoon. Do I need to mix it now?

Irvine, You're going to be the algae expert here when you're done! I can't advise you on algaecides, but I think you should mix up anything you pour into your pool at least so it doesn't puddle in one place. You can add more than a cup or two of chlorine -- try a quart at the spot, but then I'd use the pump or a brush or something to stir it up it that area.

That's what I would do and, pending advice to the contrary this evening from those who've done this, that would be my recommendation. Tomorrow, start filling the pool!

 

[irvinenewbie]

I can't advise you on algaecides, but I think you should mix up anything you pour into your pool at least so it doesn't puddle in one place. That's what I would do and, pending advice to the contrary this evening from those who've done this, that would be my recommendation.

oh, didn't add algaecide, just bleach. ok, i'll go stir. thanks.

 

[irvinenewbie]

I'm a bit disappointed pool drained by uncertain amount. test results taken about 2hr after pump/filter on. water is sparkling.

FC 3
CC 0
pH a bit higher than 7.8
TA 140
CH 370-380 (a drop may have gone in accidentally)
CYA 60
temp 75F

Obviously I didn't drain enough. I do not want to drain more and refill if I can help it. Water is quite expensive here.

Other mistake: did not drain spa, which has spill over to pool. plumbing is such water goes from filter to spa, then spills over to pool. spa was sitting un-circulated in 80F weather all day yesterday while pool was being drained.

1. Do I assume the stains are algae and just shock? I don't have a way of putting liquid bleach right on top of stain to test if it'll fade. or do I do o/n chlorine loss test and see if indeed algae was present?

2. Can I just use the circulation from spa to pool spill over as aeration to bring down TA? does it make sense for TA to go up after draining?

3. I plan to run the pump the usual number of hours today (7hr), add 182oz bleach in there after sunset. If shocking is needed, I can always do that tomorrow. I can also test o/n CL loss if that's recommended. Is that the right course of action?

3. warm weather in the 80'sF in the forecast. What's most urgent? I assume bringing Cl level up.
Please advise. Thank you!

 

[polyvue]

FC 3
CC 0
pH a bit higher than 7.8
TA 140
CH 370-380 (a drop may have gone in accidentally)
CYA 60
temp 75F

Obviously I didn't drain enough. I do not want to drain more and refill if I can help it. Water is quite expensive here.

Yes, it appears the CH is still high... but the CYA is much improved! :-D You can re-test just the CH to be sure.

1. Do I assume the stains are algae and just shock? I don't have a way of putting liquid bleach right on top of stain to test if it'll fade. or do I do o/n chlorine loss test and see if indeed algae was present?

Did you try vitamin C tablet to see if it's metal-related? Most of the time sudden staining means algea. Read the 2 articles in Pool School (see that big button upper left on this page) regarding algae and shocking your pool. You're now in a much better position to shock successfully.

2. Can I just use the circulation from spa to pool spill over as aeration to bring down TA? does it make sense for TA to go up after draining?

If you're preparing to shock I would put aside concern about TA for the moment... recommend adding enough Muriatic Acid (MA) to drop your pH down from 7.8 to about 7.2-7.5

3. I plan to run the pump the usual number of hours today (7hr), add 182oz bleach in there after sunset. If shocking is needed, I can always do that tomorrow. I can also test o/n CL loss if that's recommended. Is that the right course of action?

Is the 182 oz of bleach intended for shocking? If you're planning on overnight chlorine test, allow plenty of time for whatever chlorine you add to circulate before recording the "BEFORE" first.

3. warm weather in the 80'sF in the forecast. What's most urgent? I assume bringing Cl level up.
Please advise. Thank you!

Recommend this order: 1) pH adjustment. 2) Determining whether your pool needs shocking 3) Other adjustments

 

[PaulR]

I'm a bit disappointed pool drained by uncertain amount. test results taken about 2hr after pump/filter on. water is sparkling.

FC 3
CC 0
pH a bit higher than 7.8
TA 140
CH 370-380 (a drop may have gone in accidentally)
CYA 60
temp 75F

Obviously I didn't drain enough. I do not want to drain more and refill if I can help it. Water is quite expensive here.

These numbers look not unreasonable. If your CH was 600, you drained exactly half, and the fill water has CH 80, then your new CH would be 340. What you have is not far from that. You can hope for rain over the winter to help dilute it some more. CH 380 is not horrible, just watch your pH and TA, keep them on the low side.

Your CYA is reasonable for a southern latitude.

Other mistake: did not drain spa, which has spill over to pool. plumbing is such water goes from filter to spa, then spills over to pool. spa was sitting un-circulated in 80F weather all day yesterday while pool was being drained.

This is not the end of the world either.

1. Do I assume the stains are algae and just shock? I don't have a way of putting liquid bleach right on top of stain to test if it'll fade. or do I do o/n chlorine loss test and see if indeed algae was present?

If there's some real question whether the stains are organic, I'd bring FC up to some reasonable point (e.g. 6) first, then do overnight test.

2. Can I just use the circulation from spa to pool spill over as aeration to bring down TA? does it make sense for TA to go up after draining?

Yes, and yes if the fill water has higher TA. (Read up on lowering TA, it's not just aeration.)

3. I plan to run the pump the usual number of hours today (7hr), add 182oz bleach in there after sunset. If shocking is needed, I can always do that tomorrow. I can also test o/n CL loss if that's recommended. Is that the right course of action?

3. warm weather in the 80'sF in the forecast. What's most urgent? I assume bringing Cl level up.

The answer to both question #3's is: Yep.

I see polyvue has snuck in ahead of me but I decided to post my responses anyway.
--paulr

 

[irvinenewbie]

acid first or bleach first?
how exactly do i add acid? dilute it with pool water? dilution ratio? spread it around the edge of the pool? how long do i keep pump running after adding?
I need to do something tonght.
thanks a lot!

can i also add bleach tonight after acid??

 

[polyvue]

acid first or bleach first?

Would suggest acid first... to adjust your pH -- about 1 quart (32 oz.) of 31.45% Muriatic Acid (MA) will lower your pH from 7.8 to 7.3 or so. This will prepare you for whatever shocking you might want to do.

how exactly do i add acid? dilute it with pool water? dilution ratio? spread it around the edge of the pool? how long do i keep pump running after adding?

There are 4 qts in 1 gallon of MA, so you can just pour about 1/4 of a gallon jug (or measure it if you have a quart measure) into the deep end of your pool, slowly and if possible in front of a return. The pump should be running. When I do this on my pool I set the main drain for 100% for a few minutes, but it's not absolutely necessary. You could dilute the acid first optionally. If you do, get several gallons of pool water in a large plastic bucket and ADD the ACID to the water. (Don't add water to the acid, if you see what I mean.) Then pour the diluted muriatic acid from the bucket into the deep end... again, carefully. Rinse the bucket. If you get any of this mixture on the concrete coping or deck, wash it off RIGHT AWAY with a garden hose.

After an hour of so of filtration, you should be able to add chlorine to the pool. If you add 182 oz of 6% bleach, this should increase FC from 3 to approx. 7 ppm. Keep circulating for at least another hour.

I need to do something tonght.
thanks a lot!

can i also add bleach tonight after acid??

 

[irvinenewbie]

Thank you, thank you!
retested TA and CH
TA 130-140
CH 380
so the first set of numbers are accurate.

Added 1.5gal of 14.5% MA, filter x 1hr, then added 182oz 6% bleach, filter x 1hr, testing as below:

pH 7.2
FC 7
CC 0
TA 130

Too early for TA to come down? I think I may have read that somewhere. It's all getting mixed up.
If FC loss is zero, than it's not algae, right? Then I don't have to do vitC tablet test on stain urgently since metal stain is not going anywhere and that I have to go buy some vitC tablets.

Thanks again for your help.

 

[polyvue]

retested TA and CH
TA 130-140
CH 380
so the first set of numbers are accurate.

Added 1.5gal of 14.5% MA, filter x 1hr, then added 182oz 6% bleach, filter x 1hr, testing as below:

pH 7.2
FC 7
CC 0
TA 130

Too early for TA to come down?
If FC loss is zero, than it's not algae, right?

You're sounding like a pro! I wouldn't want to tackle Total Alkalinity (TA) until I was sure the Free Chlorine retention was good. Although an Overnight Chlorine Loss test result of < 1 ppm is a good indicator that the chlorine is finding few things to oxidize (a good thing) it's not absolutely foolproof; occasionally algae is evident and must be shocked away... or at least beaten back with high chlorine levels for long periods (days and days... or weeks.)

It's probably too soon, but I wonder if the stain you see in the deep end has faded even a little? If not, you may want to buy the vitamin C and see if you get a reaction. If the brown stain were even a bit slippery... or it was spreading or clouding the pool water, I wouldn't think twice about implementing shock levels.

If for whatever reason you don't plan on shocking immediately, do nevertheless keep an eye on the FC... don't want to let it get too low.

Thanks again for your help.

You're more than welcome...

 

[irvinenewbie]

If for whatever reason you don't plan on shocking immediately, do nevertheless keep an eye on the FC... don't want to let it get too low.

You got me! Shocking sounds very labor intensive and a bit intimidating. but if it has to be done, it will get done in a timely manner.

As for the stain, I'm embarrassed to say that I don't like to put my head under the water to hold the vit C tablet over it! It's at the bottom of the 5ft end. I'm not even sure this water is healthy to swim in if it has algae. It has been too cold anyway to get in the water until the day I decided to drain my pool. I'll take a look tomorrow to see if it's lighter. I'm pretty sure it has not spread. water is clear. All the acid and bleach are added right on top of that area at water level, so maybe that'll kill it. :-D Actually I can somehow tie the tablet to the end of telepole.

Thanks!

 

[polyvue]

As for the stain, I'm embarrassed to say that I don't like to put my head under the water to hold the vit C tablet over it! It's at the bottom of the 5ft end. [...] I'll take a look tomorrow to see if it's lighter.

Actually I can somehow tie the tablet to the end of telepole.

Embarrassed? I don't see why. Your very presence in Irvine is no doubt improving the average IQ in Orange County... and California as a whole. Attaching the tablet to a pole will preserve that contribution. Don't be too intimidated by shocking; when you're ready to start, post back with any questions. You're in good company.

 

[irvinenewbie]

Thanks for your compliment, polyvue! You may want to take back your comment after seeing this post. Here's the o/n FC loss test result:

before at 9pm: 7, after at 6:30am 8!
pH around 7.2 still

hmm, if you have to ask the obvious, no, I did not add bleach in between. Given the test results, can we at least say there is NO FC loss? Or do I have to repeat the entire test tonight?

Besides testing the stain with vitC tablet, is there anything else I should do?

I will aerate with spa jets and spa spill over to bring down TA. However CSI is balanced now with the following set of new numbers( pH 7.2, TA 140, CH 380, CYA 60). Just for my understanding, do we still treat a high TA number when CSI indicates low risk of scaling (-0.21)?

Experts, is my water safe to swim in today? Just wanted to make sure before letting the kids in. Thank you very much!

 

[polyvue]

o/n FC loss test result: 9pm: 7, after at 6:30am 8! pH around 7.2 still.
Given the test results, can we at least say there is NO FC loss? Or do I have to repeat the entire test tonight?

Interesting. Was the filter running for at least a few minutes before you took your 6:30 am sample? Could be test sample variability or incomplete mixing of the chlorine with the pool water... either result is OK -- and you can always repeat the FC test. It would seem that you don't have any FC loss. If you'd like, try the Ovenight Chlorine Loss test again tonight, but I would feel comfortable with today's result.

Besides testing the stain with vitC tablet, is there anything else I should do?

Diagnosing the stain is probably the thing you want to focus on. If it's created by organics you may be able to lift it by very high (near-shock) levels of chlorine for an extended period. Another source would indicate taking a different approach.

I will aerate with spa jets and spa spill over to bring down TA. However CSI is balanced now with the following set of new numbers( pH 7.2, TA 140, CH 380, CYA 60). Just for my understanding, do we still treat a high TA number when CSI indicates low risk of scaling (-0.21)?

s my water safe to swim in today? Just wanted to make sure before letting the kids in.

Technically, aerating will just raise the pH; it's the combination of MA application (bringing down both TA and pH) and aeration that will provide the effect you want. I can see that you're keen on getting the TA down (as a perfectionist I totally understand that sentiment) but a saturation index of -.21 is not alarming. From your previous comments I know you understand that this process can be a long one, adding muriatic acid, sending the pH plummeting, followed by aeration, to raise it up again.... I'd let the kids go swimming -- not too many perfect days left!

 

[PaulR]

before at 9pm: 7, after at 6:30am 8!

The reason that the overnight-loss instructions say not to worry about FC loss of 1 or less is because the test is accurate to +/- 1 drop. With each drop worth .5ppm, it's accurate to +/- 1ppm. So, 7 in the evening and 8 in the morning is (just) within the tolerance of the test, no different than seeing 8 in the evening and 7 in the morning.

However CSI is balanced now with the following set of new numbers( pH 7.2, TA 140, CH 380, CYA 60). Just for my understanding, do we still treat a high TA number when CSI indicates low risk of scaling (-0.21)?

That CSI is for the pool? It's fine, nothing to worry about. Note that the spa is hotter and so its CSI will probably be a couple tenths higher. So, given that pH is the major contributor to CSI, keep it in line, 7.2-7.6, and you'll be fine.

The main reason to lower TA is because it contributes to pH rising quickly. This is a problem that resolves itself over time even if you don't do anything special, because you'll be adding acid to reduce pH from time to time, and that will lower TA as well. Or you can decide to go after it aggressively, introducing lots of aeration so you can add acid more frequently.

 

[irvinenewbie]

Thanks very much, polyvue and paulR! Your explanations make sense.

That CSI is for the pool? It's fine, nothing to worry about. Note that the spa is hotter and so its CSI will probably be a couple tenths higher. So, given that pH is the major contributor to CSI, keep it in line, 7.2-7.6, and you'll be fine.

The CSI data numbers are for the pool. There is constant water flow from spa to pool. I checked water temp for both spa and pool from the heater, they are the same. So I should be fine. Just to make sure, are you saying that I should keep pH at 7.2-7.6, which is lower than recommended level of 7.5-7.8 until TA comes down to normal range? I understand I don't need to do anything aggressively as long as CSI is fine.

As for the stains, they are much lighter than a week ago. vit C test was equivocal, but leaning towards metal. the splotches are so small, maybe it lightened it, maybe it didn't change it. Now under the glare of sun, they are almost invisible.

by the way, my backyard smells like acid fume. Is that normal after adding MA?

we'll be swimming this afternoon! :-D

 

[polyvue]

[A]re you saying that I should keep pH at 7.2-7.6, which is lower than recommended level of 7.5-7.8 until TA comes down to normal range? I understand I don't need to do anything aggressively as long as CSI is fine.

As for the stains, they are much lighter than a week ago. vit C test was equivocal, but leaning towards metal. the splotches are so small, maybe it lightened it, maybe it didn't change it. Now under the glare of sun, they are almost invisible.

[M]y backyard smells like acid fume. Is that normal after adding MA?

I think (keeping pH in slightly lower range) is what Paul had in mind. The fumes are pretty ugly, huh? They should, however, dissipate quickly. As I recall you're using a 15% muriatic acid, so you haven't yet had the "pleasure" of getting a full face blast of 31.45% muriatic fumes!

 

[PaulR]

Yes, a lower than usual pH range is the usual way to compensate for elevated CH. There's nothing wrong or harmful with pH down to 7.2, or really even down to 7.0 although you may find it feels uncomfortable on your skin/eyes at that level.

My one experience with 14.5% MA was that it was essentially fume-free, at least compared to 31.45%. I wouldn't expect fumes to persist more than a few minutes anyway, unless you managed to spill some. Usually a "pool smell" is because of CC.

If the stains are fading without any special treatment then most likely they are organic and proper FC levels are doing what they do best.
--paulr