Help with appropriate shock for vinyl in-ground

Hi -

I tried searching the forums but couldn't find an appropriate answer to my question. I have a vinyl in-ground pool and am getting conflicting information about what type of chlorine shock to use.

I was concerned about handling/storing liquid chlorine and found the Lithium Hypochlorite to be very expensive, so at the advice of my local pool store I have been using bags of Calcium Hypochlorite. I am very concerned about bleaching and/or weakening of the liner, so I have diligently tried to dissolve the powder in a bucket before adding to the pool, but always have a residue collect in the corners of my deep end hopper. I just read elsewhere today that I should pre-dissolve and then just pour the liquid into the return stream, disposing of any remaining solids. (My pool store never mentioned about the disposal of the solids).

Can you confirm that Calcium Hypochlorite is appropriate and safe for vinyl liners if pre-dissolved? What is the residue and I can I just throw it away? Are there any other products that I should be considering? Incidentally, I concurrently use a floater with 3" tabs.

Thanks.

Jim

Hi, Jim, and welcome to the Pool Forum!

Cal-hypo is ok to use, but vinyl pool do not need calcium. (The residue will eventually dissolve.) Another choice (and what most of us do) is to just use plain, household bleach for your source of chlorine. Works great, inexpensive no residue left behind, readily available. Many of us use Walmart's generic 6% bleach. It is sodium hypochlorite just like liquid pool store chlorine is but just a different concentration. (Pool stores typically sell either 10 or 12.5% sodium hypochlorite.)

The trichlor tabs in a floater are fine for awhile but they are stabilized meaning they add CYA. All pools need some CYA but when you get too much, you have problems.

Test a set of current water testing results taken with a drops-based kit. Also, tell us the volume of the pool and the type of filter you have.

You'll need a good test kit if you don't already have one. The one we recommend is the Taylor K-2006 or 2006C (same kit, larger bottle of some reagents). If you buy it through the Amazon link in my signature, the Pool Forum makes a little money on the sale which helps us keep this form online. Only buy if the seller is Amato Industries, however. Some other sellers are substituting the K-2005 which you do NOT want.

Hope this helps!

If I might ... it depends on number of factors that need to be considered. Firstly, I ran 37 ppm CL using Cal Hypo broadcast directly around the pool when I opened this year with no bleaching of my liner (not saying anyone else should). The instructions on the HTH product say to broadcast it directly in the deep end. I too get some residue on the bottom that the robot picks up but now tend to dissolve it in a bucket first to avoid that. The other factor is how much Calcium is in your water to begin with and what your annual water replacement is. This is true also of CYA. Being in Ontario I have to close my pool for the winter and can count on at least half of the water being replaced every year. So I can run the season without getting to levels that cause problems. Bleach is not the best value for me in my market area or I WOULD use it ... I'm just suggesting that it's not the only option based on the other factors.

Quote:

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Originally Posted by Watermom

Many of us use Walmart's generic 6% bleach. It is sodium hypochlorite just like liquid pool store chlorine is but just a different concentration. (Pool stores typically sell either 10 or 12.5% sodium hypochlorite.)

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Thanks for the friendly welcome. This is a really great site.

I have done some reading on the BBB method and am intrigued. I'll post my most recent numbers when I get home from work, but as of last check I've got my pool seemingly dialed in with current (albeit expensive) regimen. I'd certainly be interested in converting to a more cost-effective system, but don't want to mess anything up.

Can I transition into a modified BBB? I expect that the calcium hypochlorite will be the first thing that I'll run out of. If so, how much 6% bleach would I use to shock a 25,000 vinyl pool? Can I continue to shock with bleach but use my 3" pucks in the floater?

Thanks.

Jim

In a 25K gallon pool, each 2 gallons of 6% bleach will raise your FC by 5 ppm, so you can use that as a guide. As to how high your chlorine needs to go, that will depend on your CYA level. If you can see the blue links at the bottom of Watermom's sig, click on the "best guess chlorine" table to tell you how high your Cl needs to go, based on your CYA level. You can absolutely shock with bleach and still use your tabs in the floater, IF your CYA level is not too high--most folks keep it around the 40 ppm range.

Janet

Quote:

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Originally Posted by aylad

In a 25K gallon pool, each 2 gallons of 6% bleach will raise your FC by 5 ppm, so you can use that as a guide. As to how high your chlorine needs to go, that will depend on your CYA level. If you can see the blue links at the bottom of Watermom's sig, click on the "best guess chlorine" table to tell you how high your Cl needs to go, based on your CYA level. You can absolutely shock with bleach and still use your tabs in the floater, IF your CYA level is not too high--most folks keep it around the 40 ppm range.

Janet

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Thanks, Janet.

Here are my numbers from 6/24:

FC 1.5
TC 1.5
CC 0
pH 7.7
Hardness 230
Alk 83
CYA 25
Copper 0.1
Iron 0

I brought the ALK up slightly after this test. I use 3" tabs in a floater and shock every 7-10 days with Calcium Hypochlorite.

I'll review the Best Guess chart again this evening. I looked at it briefly at work today but wasn't quite clear on how to read it so I'll see if it makes more sense now.

Jim

Why do you shock it so often? Unless you're having a problem, see algae starting, or are losing chlorine overnight, there's really no reason to shock it on a regular basis. However, with your CYA at 25, you need to keep the chlorine between 3 and 6 ppm at all times. Be careful about shocking with the cal-hypo, though--your calcium level is climbing, and it won't be too much longer before you start having cloudy water issues due to the calcium....

With the best guess chart, the left-most column shows your CYA level, the next one shows the minimum and maximum chlorine levels that you need to keep in your pool for that CYA level, and the next column shows how high you need to take your chlorine to achieve "shock" level. The right-most column is for those who have mustard or black algae, or some other water problem that does not respond to normal shock levels.


Janet

Quote:

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Originally Posted by aylad

Why do you shock it so often? Unless you're having a problem, see algae starting, or are losing chlorine overnight, there's really no reason to shock it on a regular basis. However, with your CYA at 25, you need to keep the chlorine between 3 and 6 ppm at all times. Be careful about shocking with the cal-hypo, though--your calcium level is climbing, and it won't be too much longer before you start having cloudy water issues due to the calcium....

With the best guess chart, the left-most column shows your CYA level, the next one shows the minimum and maximum chlorine levels that you need to keep in your pool for that CYA level, and the next column shows how high you need to take your chlorine to achieve "shock" level. The right-most column is for those who have mustard or black algae, or some other water problem that does not respond to normal shock levels.


Janet

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Thanks again, Janet -

So to confirm that I'm understanding the Best Guess chart, assuming that my FC is 1.5 and if I round my CYA up to 30, would I add approximately 5 gallons of 6% bleach to achieve an acceptable "shock" of 15 ppm?

For my current practice, my local store recommended shocking 1x/week with the Calcium Hypochlorite. I've extended it to once every 10 days or so but now realize that even this may be overkill. The kids are in it literally every day so I've been trying to avoid getting behind the 8-ball with the chemicals.

Another question: the pool store told me to keep the FC between 1-3ppm. They didn't seem concerned about the CYA so long as my FC level stayed within reasonable limits. Should I be keeping it higher?

Jim

The Best Guess page -- linked in my signature -- answers most of the questions you asked. Read it, and then we'll try to answer those that remain.

Also, trichlor pucks are stabilized which means they add CYA. So, if you are going to continue to use them, you'll need to check your CYA every week or two. For every 10ppm of chlorine that the pucks add, they also add 6ppm of CYA. When your CYA hits about 50, you'll need to stop using them or your CYA level will get too high. At that point, just use bleach for your daily chlorination needs as well as shocking when necessary. (I rarely shock my pool. As long as you don't let your cl level fall lower than the minimum on the range listed in the Best Guess chart, you shouldn't need to shock.)

Hi Jim,

Where about's are you and how much sunshine does the pool get per day?

Quote:

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Originally Posted by DurhamHouses

Hi Jim,

Where about's are you and how much sunshine does the pool get per day?

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I'm in the suburbs of Philadephia, PA. Pool is on the east side of my house so it gets direct early and mid-day sun.

Ben, thanks for pointing me to the link. I have read it literally about 10 times but am still trying to get my head around the logistics of convering to a full or modified BBB regimen. I just bought a new 25 gallon tub of pucks so I'll plan to at least finish those out before I try anything drastic.

A 25 gallon tub of trichlor sounds like a lot of trichlor. Keep an eye on your CYA if you use these. It will climb faster than you think.

Quote:

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Originally Posted by Watermom

A 25 gallon tub of trichlor sounds like a lot of trichlor. Keep an eye on your CYA if you use these. It will climb faster than you think.

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Sorry, meant to write 25 pound tub. I agree that a 25 gallon tub would be a boatload of trichlor.

Even still, if you use more trichlor, keep an eye on your CYA level and also on your pH level.

The great thing about the B-B-B method is at its simplest, it's very, very easy.
The one KEY thing is you need to be able to test properly, which is why we recommend the Taylor K-2006 or an equivalent FAS-DPD test kit (Leslies has one, so does another pool forum).
You should also have a simple OTO/pH kit, preferably one that measures chlorine to 5ppm. The Taylor K-1000 is the best and costs about $10.

You test with the OTO every day and adjust your chlorine and pH as needed (I haven't had to adjust pH in 6 weeks).

Once a week you test Free Chlorine (FC), Combined Chloramines (CC), pH, Total Alkalinity (TA), and Stabilizer/Cyanuric Acid (CYA).

If you have a concrete/shotkrete/gunite/plaster/tile pool, you test Calcium Hardness (CH) as well.
But if you have a vinyl pool you only have to test it twice a season (unless you use lots of Cal-Hypo).
And, if you have a Salt Water Chlorine Generator you need to test for salt,too.

Your ideal daily level of Chlorine is determined by your weekly test of stabilizer, as well as the Best Guess Chlorine Chart (See Ben's and Watermom's sig for the link). So...my CYA level is 30ppm. Therefore my daily chlorine level should be between 3 and 6 ppm. As long as it stays in that range, or doesn't fall to far below it for long, I don't have to shock. It works out that I have had to add about 1 gallon of 6% bleach every other day for almost 20,000 gallons. Simple.

pH? As I said I haven't had to adjust it in over 6 weeks---but that's because I check it and watch it. If it gets low, I can add Borax (which adds borates and can inhibit algae), or I can aerate, which adds nothing, but raises pH. If it's high I can add Muriatic Acid or Dry Acid (the generic for Low'n'Slow)

Once a week I "worry" about mainly T/A and CYA. Since my pH has been stable at 7.6, I haven't done ANYTHING to change my unusually low T/A of 60ppm. T/A's JOB is to buffer and stabilize pH. My pH is stable, I don't mess with it.
Since I've had to add the bleach (Actually, I use Liquid Chlorine and 1/2 gallon of that is the same as one gallon of bleach) at the rate of 1 gallon every other day, I'm planning to raise CYA to 50 or 60 and maintain chlorine at the 5 to 10ppm level.

I have a vinyl pool, I never add Cal-Hypo, so, I measure my Calcium Hardness twice a season. It was at 60ppm early on and I'll probably measure it at the beginning of August, just to be sure.

If you stick with bleach, Borax, Baking soda, Muriatic Acid/Dry Acid and 100% Cyanuric acid, you don't need anything else in your pool but kids and fun.

It's very possible to work with Tri-Chlor tabs, Di-Chlor powder, Cal-Hypo, chlorinators, etc. and STILL follow the B-B-B method. You just have to know what each product does and keep an eagle eye on your daily and weekly tests. So...if I'm using Tri-Chlor tabs, I'm seeking to do 3 things: Keep a constant flow of chlorine, lower my pH, and raise my CYA level. I could do each separately, but sometimes this is more convenient.

2 caveats.
Do NOT use ANY algaecide but 60% polyquat (60% Poly....<something>... and no other active ingredients). Other algaecides do more harm than good.
HTH products are now "cocktails" of things you may not want, like "double acting tablets" that contain tri-chlor AND copper, which stains fittings and turns blonde hair green. Always check the label. The Namco chain in my area is no longer selling 100% CYA--they mix it with Soda Ash (which is far cheaper but don't tell you how much). Soda Ash raises both pH and Total Alk.

Carl

Carl made a little typo. We recommend the Taylor K-2006, not the K-2005.

I also do things just a little differently than he does. I don't check my CYA weekly. After I get my CYA where I want it early in the swim season, I don't test it anymore that summer. I can do that since I don't use any forms of stabilized chlorine like trichlor pucks or dichlor powder. I only use bleach.

I was wondering about that as well. If you know what your CYA is then just keep track of what your putting in the pool. If its 6ppm per 10ppm of chlorine you should be able to calculate based on the pucks used.

Good catch, Lisa...can't believe I did that:mad:

A lot of people are leery of testing CYA so often because they quickly run out of reagent. I simply order pint bottles of the stuff from Amato, so I don't have to be parsimonious about using it.

You can estimate how much CYA you have but it's like trying to drive down the street with a compass, a stop-watch, and a map, rather than looking out the windshield.

But we all have our different styles and Jan's been making her pool run beautifully since she was a little tyke! :D

Carl

Uhhhh ........ not Jan. That would be Lisa! :p:p

That's what I said, "Lisa" :p:D:o:rolleyes::confused:

Thank you, everyone. Carl, I appreciate the detailed information that you shared. It really helped to fill in a couple of blanks that I had. Since my CYA is still low and I'd just purchased a bucket of tabs before considering the BBB method, my plan is to try to transition from my current regimen into a BBB. That being said, I have a couple more questions/clarifications:

1. I have a Leslie's DPD test kit. I can determine FC, TC, Alk and Acid Demand. With this exception of CYA, this will work for the time being right?

2. My daily chlorine level tends to stay in the 2-3ppm range and I see very slight algae growth in the corners every few days now that I've backed off on the weekly shock. Can I continue to use the tabs and boost my chlorine with a small daily addition of bleach?

3. Lastly, I still don't quite understand (or maybe it's more a matter of confidence in my understanding) the recommended daily chlorine levels. A regular level of 5-10ppm just seems awfully high based on what I'm being told elsewhere. My pool store recommends keeping it around 3ppm and my test kit says to keep it between 2-4ppm. In fact, the range on my color chart only goes to 5ppm. What am I missing? Is it because the BBB method corrects for CYA? Assuming that my Leslie's DPD kit is appropriate, how do you even determine a chlorine level >5?

Jim

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Originally Posted by jeepers

3. Lastly, I still don't quite understand (or maybe it's more a matter of confidence in my understanding) the recommended daily chlorine levels. A regular level of 5-10ppm just seems awfully high based on what I'm being told elsewhere. My pool store recommends keeping it around 3ppm and my test kit says to keep it between 2-4ppm. In fact, the range on my color chart only goes to 5ppm. What am I missing? Is it because the BBB method corrects for CYA? Assuming that my Leslie's DPD kit is appropriate, how do you even determine a chlorine level >5?

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I'll answer the easy bit, first. Use the Amazon page (linked in my signature) and order the K1515 which adds only the DPD-FAS chlorine test. I think Leslie's kit is a private label K2005, so when you add the K1515, you have a K2006.

Ok, the harder bit.

Yeah, we tell people to maintain MUCH higher levels than the various standards and labels do. But here are some facts to consider:

#1 - When I first started recommending higher chlorine levels than the rest of the pool industry, way back in 1996 with PoolSolutions, 2 things were true:
(a) EVERYBODY in the pool industry, including the US EPA was saying 3 ppm was the absolute maximum chlorine level in swimming pools, BUT
(b) At that same point in time, the Federal potable water standards --- set by the US EPA -- had NO upper limit on chlorine in DRINKING water.

The result? People filled pools with water that -- according to the EPA -- was safe to drink, but that wasn't -- according to the EPA -- safe to swim in, till the chlorine levels (sometimes > 5 ppm!) dropped. You could drink it, cook with it, and bathe your baby in it . . . but not swim in it.

#2 - More recently, the US EPA has revised drinking water rules to include a 4 ppm "action level" on chlorine in drinking water. This means if your local water company accidentally overfeeds chlorine, and finds they are shipping water with 10 ppm FC, they have to take "action" to correct the over feed. BUT, the required action does NOT include having to tell their customers that they may -- right now -- be filling their pools with water that has too much chlorine to swim in.

#3 - But, the fact is, 5 ppm is unnecessarily high in pools . . . if you have no stabilizer. Chlorine levels that high in unstabilized indoor pools seem to serve no useful purpose, and they ARE slightly more irritating (absent stabilizer) than lower levels are.

#4 - HOWEVER, we don't recommend levels above 5 for unstabilized pools -- please read the Best Guess page linked in my signature below. Rather, we recommend increasingly high chlorine levels as stabilizer levels go up. Why? Because stabilized chlorine is essentially chlorine "in reserve" -- it's available to be "called up for active duty", but until the small fraction of chlorine in a stabilized pool that IS on "active duty" is consumed, the rest of the chlorine remains largely inactive.

So, the bottom line is, 20 ppm FC in a stabilized pool is more like 1 ppm FC in an unstabilized pool, than it is like 3 ppm in a stabilized pool.

#5 - What's more, the national pool organizations (NSPF, NSPI => APSP, and even the CDC) are have gradually recognized what we've been saying here. They haven't quite caught up, but they are moving in that direction. Maybe in another 15 years, they'll agree with us!

#6 - The EPA, and chlorine product labels, are another matter. These labels are regulated under a very cumbersome Federal Act, generally referred to as FIFRA. A very elaborate and expensive process is required to change these labels even trivially. A change in safety guidelines is worse. And, the cost is borne by the product manufacturer. However, they have NO incentive to spend that money, for an extremely simple reason: you, and millions of other pool owners, will use LESS chlorine, if they fix the labels -- so people maintain higher levels of chlorine -- than if they leave them alone, resulting in people continuing to maintain inadequate levels of chlorine.

So they are faced with the reality that, if they spend money to FIX the labels, they will LOSE money in sales and profits as a direct result. Thanks to current rules regulating publicly owned companies, they could even be sued by stockholders for acting in a manner that decreased stockholder assets and earnings!

#7 - It's very popular these days in the MSM to talk about, or report on, the dangers of chlorine. (Actually it may have slacked off a bit from a couple of years ago). But, the research that underlies most of these idiotic reports -- and there is some genuine research -- is most often about 1 of 2 things. Either it is reasearch into the LONG-TERM (50+ year) effects of "DBPs" (Disinfection , ie chlorination, By Products) in drinking water. Or, it is on the effects of DBPs or "THMs"( Tri-Halo-Methanes, a particular class of DBPs) on users of INDOOR pools. There *is* something to this research, especially the indoor pool effects. But what you have to keep in mind is that the implications of this research, which are NOT accurately reported as a rule, are for "water drinkers" or for "indoor pool users". The information we provide here at the PoolForum has NOTHING to do with water you drink (or at least, it shouldn't!), and we rarely deal with indoor pools. For what it's worth, when I do make indoor pool recommendations, I do try to recommend things that will reduce DBP formation in indoor pools -- see this unfinished thread.

Hi Jim,

I think a lot of fears come from the misunderstanding that it's the chlorine (higher levels) that causes problems with bather comfort. In fact it's low chlorine levels that causes the problems and PH levels have way more impact on eye comfort etc. Smell that chlorine smell ..that's cause by high CC levels and inadequate FC. Now high chlorine might eat your bathing suit if you don't rinse it but as I understand it it's hard to hurt people with Chlorine until you get very high levels. With CYA you are trading effectiveness for longevity. Chlorine loses some of it's "work value" when attached to CYA. So where .1ppm with no CYA might kill a bug in 5 seconds with a CYA of 70ppm it might take 20 minutes. That's why you need to run higher levels of residual chlorine. It's like having a surplus in your bank account or an insurance policy. If it's needed it gets used and if it isn't needed then it sticks around instead of being eaten by the sun. The fact that you have algae in the corners demonstrates that the CL levels are too low. Shocking isn't a maintenance item but rather a method to combat a specific issue such as algae blooms or a CC level of more than .5ppm I believe. I have a CYA of 55 and float my chlorine levels between 4-9ppm. It was 4ppm last night and I added another 4ppm which will last me a couple of days. Everyone remarks on how nice the water feels and how they don't like high chlorine levels in pools ..I just smile.

Thanks a million Ben. I am amazed (and admittedly somewhat overwhelmed) by your lessons. Great info and lots of food for thought.

Two quick follow up comments:

1. I will go online and get the K1515 kit that you recommended. I checked and my Leslie's DPD is a re-branded Taylor kit.

2. My float full of tabs seems to hold me steady at only about 3ppm with a currently low CYA. Am I safe to add the daily doses of bleach as an adjunct to the floater to bring up my daily chlorine?

Thanks again.

Jim

Yes. Many people use trichlor pucks and bleach in their pools. Just keep an eye on your pH if you use pucks as they are very acidic and will drive the pH down. Also, monitor the CYA every couple of weeks and when your CYA hits 50, discontinue using the pucks.

Quote:

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Originally Posted by PoolDoc

I'll answer the easy bit, first. Use the Amazon page (linked in my signature) and order the K1515 which adds only the DPD-FAS chlorine test. I think Leslie's kit is a private label K2005, so when you add the K1515, you have a K2006.

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Ben -
I'm ready to order my kit but wanted to clarify. If I augment my Leslie's/Taylor kit with the K1515, will be I be able to run CYA? It looked like the K1515 may just be a chlorine test and I don't currenty have a CYA test in my existing kit. Does this change your recommendation any?

Thanks again.
Jim

Yeah, get the complete K2006 or 2006C.

If your Leslie's kit doesn't include CYA, it's not a rebranded K2005. Your three critical tests are pH, DPD-FAS chlorine, and CYA.