Using stabilized pucks with BBB (to make life easier)

[wes8398]

I've been succesfully using the BBB method since I opened my pool this spring. My wife and I both work 12 hour shifts, and the nightly addition of chlorine is a bit of a neuisance. I'm wondering about going to the local hardware store and buying a big bucket of stabilized pucks, but I'm concerned that a) they might not keep my FC levels where they need to be, and b) I wonder how much CYA they add to the water (per 200g puck). With weekly backwashing and cleaning, I'm not too concerned about CYA building up too much, but I don't know how much these pucks generally add to the water.

Any insight?

 

[JohnT]

If you have normal chlorine demand, your CYA will go up about 2ppm per day with pucks. In one month, even if you changed half the water in the pool with backwashing, you'd increase about 30ppm.

 

[257WbyMag]

Have you thought about getting a SWCG?

 

[wes8398]

If you have normal chlorine demand, your CYA will go up about 2ppm per day with pucks. In one month, even if you changed half the water in the pool with backwashing, you'd increase about 30ppm.

Wow...that much, eh? 2ppm per day?? I figured a whole puck might put that into the pool. This BEGS the question though ... how did my step-father's pool test under 10ppm CYA (TF-100) upon opening this year when he's used tri-chlor pucks religiously for the past 5 years? Since most say that CYA stays in your water and the only way to bring it down is to dilute - where has all his CYA gone?
Anyway, maybe I'll stick to having to add the chlorine nightly and just use the pucks when I'm away. Or, is there such a thing as a chlorine puck that doesn't include the CYA? And also isn't Cal-Hypo? On that note, how much chlorine does any puck put into the water?


And yes, I thought about an SWG, but I simply just don't buy into it. It seems like an unnecessary waste of money to convert over to it.

 

[JasonLion]

CYA sometimes disappears over the winter. It is common for this to happen, though not reliable enough to depend on.

 

[Kes]

Hi Wes,

I'm sure the exact figures are in this forum somewhere, but on my 10k imp gallon pool one 200 g trichlor tab lifts the chlorine level by approx 3.5 ppm. Your pool is around twice the size of mine (ours!) so one tab for you equals 1.75 ppm chlorine. CYA is 0.6 of the chlorine dose, so you would add a gnat's elbow above 1 ppm cya per tab. Bear in mind that this is over one week, or the time it takes for the tab to dissolve.

I don't know about your daily chlorine use, but if you were to add 2 ppm cya per day using tabs, you would be using 14 tabs a week. This seems rather excessive to me.

For over twenty years we managed our pool using ignorance, trichlor tabs and a small phenol red/dbd1 tab tester. The process was the same, open pool, pool goes green, fight green by guesswork, pool amazingly clears, add one tab a week until pool close time. The water was never drained, apart from rare vacuuming and occasional backwashing, for all those years until we had a new liner in 2008. I didn't know what cya was, let alone how to measure it. Yet the pool remained sparkly clear (after the green fight) at 2-3 ppm free chlorine and what must have been sky-high cya. Trichlor tabs seem to be held in worse esteem than garlic to a vampire, yet I think that they are a quite acceptable proposition in a managed pool. After getting a better test kit I have reduced my cya to 35 (ish), and I am using cheap weak bleach at the moment, but I would have no qualms about using, or even reverting, to trichlor tabs in the future. Certainly that's what will happen when I'm carried off to the old gits home.

 

[chem geek]

The point seems to be missed that high CYA from continued use of stabilized chlorine does NOT GUARANTEE that a pool will get algae or become cloudy or unmanageable. It just significantly increases that risk. If the pool is naturally low in algae nutrients (phosphate, nitrate) or has some form of algaecide in it then algae growth may be inhibited or prevented. Or one could have the CYA drop each winter or get diluted from rains or have regular shocking kill off algae that starts to grow during the week. So if one wants to use Trichlor as their sole source of chlorine, then go ahead since it's your pool and you can do whatever you want with it.

It's statistics, just like a smoker saying that because they have smoked all of their life and didn't get cancer (or a stroke, etc.), that it must be a lie that smoking increases the risk of getting cancer or a stroke. One should not project one's own personal experience to everyone else for processes that are statistical in nature. It's fine to share the experience as a data point, but it doesn't prove anything with regard to what happens in a large population of pools.

There are hundreds of new forum members each summer who report algae or cloudy water or chlorine demand problems that are most frequently correlated with high CYA (or too low an FC for the CYA level). There are also pool services managing thousands of pools who have also found that in order to prevent algae they either can't let the CYA get too high (usually over 100 ppm) or they must operate with a higher FC level than the 1-3 ppm "recommended" or both. It would be inaccurate to only look at the subset of pools with high CYA and no algae and declare that there must not be any correlation. There are over 14,000 members at TFP and at one time over 20,000 members at The PoolForum most of whom manage their pools with an appropriate FC/CYA ratio and with very, very few getting algae (except for letting a pool go over the winter without chlorine). The failure rate is far less than 1 in 1,000 -- probably more like 1 in 5,000 or better.

Richard

 

[wes8398]

Chem Geek - I think you misunderstood what Kes was trying to say. He/she wasn't arguing the statistics behind CYA levels at all. Kes was simply saying that it's possible that Tri-Chlor pucks don't build up CYA as quickly as some think. We've gone from one person stating that Tri-Chlor pucks add 2ppm CYAPER DAY, to another person who seems to have tested this theory and found that the pucks add just over 1ppm PER WEEK (since most pucks last ~ a week). Now I'm not sure how Kes tested this, since I would think that testing for 1-2ppb differences in CYA levels would be quite difficult, but... Anyway, the latter seems more reasonable to me, but I'm no scientist and I've never done the testing to figure it out, so I just don't know (which is why I was asking). Do you happen to know the ACTUAL numbers behind how much FC and CYA a 200g tri-chlor puck adds to one's pool? Is there a way to figure this out by the percentages and ingredients listed on the product's packaging?

 

[JasonLion]

Trichlor adds 0.6 ppm of CYA for every 1.0 ppm of chlorine.

In 25,000 gallons, a 200g pure trichlor puck will raise FC by 1.9 and CYA by 1.2. Nearly all trichlor is 95+% trichlor, so using the "pure" numbers is normally close enough.

Using only one trichlor tablet a week in 10,000 gallons in an outdoor pool is stretching things pretty thin at low CYA levels, but could be achieved at higher CYA levels. With the right kind of solar cover, chlorine usage could be gotten down well below that.

How quickly CYA goes up has a great deal to do with how quickly you use chlorine. If a pool uses 2 ppm of chlorine a day from trichlor it also gets 1.2 ppm of CYA, or about 36 ppm of CYA a month. But if the pool is only using 0.5 ppm of chlorine a day it will only be gaining about 9 ppm of CYA a month. Various forms of water replacement (splash out, backwashing, overflow) will bring either of those numbers down somewhat, though not usually all that much.

What really gets people in trouble quickly is using dichlor to shock. Dichlor adds 0.9 ppm of CYA for every 1.0 of chlorine, and when you are shocking you add a lot more chlorine a lot more quickly.

The common CYA test is +-15 on a good day (and most of the others are worse). Using that to measure CYA changes over time requires large changes in your CYA level before you will get any useful amount of precision. For example, measuring a CYA change of 30 could actually indicate a change of anything from 0 to 60 (two CYA tests are involved, so double the error), which means that result is essentially useless.

When using trichlor exclusively, you need to either have a substantial amount of water replacement, or lose CYA over the winter. Otherwise CYA just keeps on going up and up. Trying to use trichlor with a cartridge filter is way more problematic than using trichlor with a typically undersized sand filter (that needs to be backwashed frequently).

 

[svenpup]

Having never used the pucks, I find this topic interesting.

So, how do you maintain a given FC? What determines how fast a puck dissolves?

I could put one puck in a pool that has a 3ppm per day FC load. If that puck lasts a week that doesn't mean I only have .4 ppm load. Rather, it means that I barely had any FC for the whole week as it was consumed as fast as the puck could release it.

 

[wes8398]

JasonLion - Thanks for the useful info! Although some facts beg more questions, I don't think it'll get me any further even to have those questions answered, so I wont bother with most of 'em.
One thing I find interesting with those numbers is that I don't understand how I ran a roughly 35,000 gallon pool - algae free - for 2 summers (June to October) with only 200g tri-chlor pucks (one a week) and once a week non-chlorine shock. Without considering the weekly "shock", according to your numbers, I was only adding 1.2ppm of FC per week ... that's nothing. I guess that shock must have boosted FC A LOT.

Anyway...I think what all this boils down to is that I don't really want to use the pucks unless I have to. I'll stick with the regular "BBB" method and "leave well enough alone", as my Mom would say.

 

[JasonLion]

The speed at which pucks dissolve depends on the water temperature, the dissolve more quickly in warmer water, and the setting on the chlorinator. The temperature variation thing is kind of nice, because you need more chlorine in warmer water. If you have a tablet chlorinator, it will have a valve that controls how much water flows over the tablets. If you have a floating tablet dispenser, it will usually have a sliding panel that lets you control how much water moves through the dispenser.

Shocking once a week does count towards total chlorine usage. A typical shock once a week instruction is something like 1 lb of cal-hypo per 15,000 gallons, which works out to about 6 ppm of chlorine. If you are shocking with cal-hypo you will eventually run into calcium problems, though that takes longer to become an issue than CYA typically does. If you are shocking with dichlor, it is even worse than using trichlor, raising CYA by 150% of what trichlor raises CYA by.

 

[Isaac-1]

I am not an expert on the topic, but from what have read excessively high CYA levels require higher FC for safe sanitation and make shocking with chlorine a practical impossibility. From what you have said, you had a possibly unsafe low daily FC level however you were shocking weekly with a non chlorine shock (MPS I assume), this would still allow shock level oxidation without being effected by high CYA since you were not using Chlorine to do the shocking. If you had added enough trichlor to maintain a safe FC level it would quickly turn into a run away condition.

Ike

p.s. My math puts 1- 200 gram trichlor puck closer to 1.35 ppm on a 36,000 gallon pool, which by chance is roughly my weekly chlorine demand with an indoor pool with a light bather load, by chance was this pool in a heavily shaded area?

 

[chem geek]

Chem Geek - I think you misunderstood what Kes was trying to say. ...
Do you happen to know the ACTUAL numbers behind how much FC and CYA a 200g tri-chlor puck adds to one's pool? Is there a way to figure this out by the percentages and ingredients listed on the product's packaging?

Yes, I may have misunderstood the point. If it's about how quickly CYA builds up, it's not a debate. It's a chemical fact because CYA isn't "added" to Trichlor, it is chemically a part of Trichlor. However, as Jason pointed out there are ways for CYA to decrease, mostly through dilution (backwashing, splash-out, rain overflow) and sometimes through the large winter reduction sometimes resulting in ammonia. There is also a slow chlorine oxidation of CYA itself, but that's only on the order of 2 ppm CYA or so per month in most cases.

As for actual experience with the CYA buildup, this happened in my own pool 7 years ago when I was using Trichlor pucks in a floating feeder. My pool was 16,000 gallons and I used up around one 8-ounce Trichlor puck every 5 days where the daily chlorine demand was around 0.7 ppm FC per day (I have a mostly opaque electric safety cover so not too much exposure to sunlight). I started out with 30 ppm CYA in the pool and after 1-1/2 years (11 months of this chlorine demand; over the winter it was < 1 ppm FC per week) my CYA was 150 ppm. It's no mystery that my CYA rose because the increase in CYA was theoretically 0.7*30*11*0.61 = 141 ppm so with the 30 ppm initial that's 171 ppm which was close to the 150 I had, especially accounting for a small amount of dilution (and test error, etc.).

I have an oversized cartridge filter only cleaned once per season and I have virtually no summer rains and during the winter I used a pool cover pump that put the rain water into the drain, not into the pool. So my pool had very little water dilution. I also maintained the chlorine level over the winter (we don't get hard freezes) so didn't lose CYA over the winter.

 

[Kes]

My little anecdote was really just to show how I laboured under ignorance before finding this forum, with a comment that perhaps trichlor is not quite, or doesn't have to be, the baddie it's frequently portrayed. I would certainly not advise managing by ignorance in any field.

Ah! I've just found a poolstore water analysis from 2002 (15 years after liner change and water fill).

FC 0
TC 0
PH 7.2
TA 60
CH 120
CYA 100

Algae none, Clarity clear.

If I could tot up what they recommend..... Just under 25 kg of chemicals, 1.65 litres of 'Pool Magnet', and Deep Cleanse Filter Cleaner. Plus 413 gm Bio Shock and 164 ml Algae Inhibitor every two weeks. Needless to say I didn't buy any of that, well, the pool was clear, so I guess I continued with my one tab a week.

Anyway, this is far enough off topic.

Oh yes, one tab a week (3.5 ppm chlorine) may seem low but there's not usually a lot of sun in the UK - except this week.

 

[prov431]

And yes, I thought about an SWG, but I simply just don't buy into it. It seems like an unnecessary waste of money to convert over to it.

I don't agree....a SWG totally simplifies life. We did the bleach method for 3 years, and it seemed like the way to go.....but it gets really old lugging bleach, stocking it & dumping it every day. We supplemented with pucks while we were away, and had mixed results. On top of that, when the weather here in southern NC gets hot (my 32x16 IG pool temp is 92 right now), it's very difficult to keep up with the chlorine demand.
Moral of the story...we installed a SWG (total cost including salt, fittings, etc was $1040) and life has never been easier. The SWG keeps the pool absolutely perfect, and we don't do a thing now but enjoy the pool. Between the SWG and the automatic vacuum, maintenance is practically zero.

 

[wes8398]

I really haven't looked into it much, besides the price and the basics. It does sound swell, but the conversion cost is too high for me right now. They seem to be steadily declining in price, so maybe I'll be more inclined to convert at a later date. By the way - where does all the cost come from for conversion? Parts? Install?

 

[Beez]

I've been succesfully using the BBB method since I opened my pool this spring. My wife and I both work 12 hour shifts, and the nightly addition of chlorine is a bit of a neuisance.

Hey Wes, how often do you use your pool? Many people here do not add chlorine every day, but every couple or three days instead. It all depends on how much use the pool gets. My own pool is not used at all during the week, so I add bleach only a couple of times a week. Just another thought... :idea:

 

[prov431]

I really haven't looked into it much, besides the price and the basics. It does sound swell, but the conversion cost is too high for me right now. They seem to be steadily declining in price, so maybe I'll be more inclined to convert at a later date. By the way - where does all the cost come from for conversion? Parts? Install?

Its a DYI project, takes about an hr to put it in.
Costs are:
SWG (includes transformer/control module & cell) ~$700-1100 average for in ground pool, I paid $860
Salt $150 (for 680 lbs, 21,000 gallon pool)
PVC fittings / glue- $9.00

Over time, IMO what you will spend in bleach, going to the store, time, etc...the SWG will pay for itself. Once it's up and running pool maintenance is truly simplified.

 

[wes8398]

I've been succesfully using the BBB method since I opened my pool this spring. My wife and I both work 12 hour shifts, and the nightly addition of chlorine is a bit of a neuisance.

Hey Wes, how often do you use your pool? Many people here do not add chlorine every day, but every couple or three days instead. It all depends on how much use the pool gets. My own pool is not used at all during the week, so I add bleach only a couple of times a week. Just another thought... :idea:

The pool gets used for a 10 minute dip on a daily basis, but there's rarely a heavy bather load. I have been adding 2 litres of 12% chlorine on a nightly basis (which gets FC up to about 3.5ppm), and by the next evening it's down to about 1ppm again. The pool gets full sun from dawn to dusk, and CYA is at about 35ppm. I figure 2.5ppm chlorine usage is pretty normal, given the amount of sun the pool sees. I definitely wouldn't want to go 2+ days without adding any chlorine though - unless I wanted to bring it up to 6ppm on the night I add it, then let it drop down over a couple days.