More than usual chlorine consumption.

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paokaras31

paokaras31

0
Jun 25, 2013
26
greece
Hello every one!
This season has been great so far except for a minor issue.
Water is sparkling clear first of all and has been since April. However compared to last year I need to run my SWG at 50% compared to 30% last year to keep my target FC for my CYA level. My CYA is 60 this year and it was also 60 last year.
[ I manage to get off with lower than 70-80 because I have an oversized Salt & Swim Hayward SWG (the cell has lasted by the way for 2 1/2 years for a cost of $200 , I dont winterize the pool it is open year round) and run the (undersized) pump 14-16/24 from May- September 8-10/24 October-December 4-6/24 January, pump off February and March and so on..Very hot summers here in southern Greece and mild winters.]
There is obviously something in the pool that uses more chlorine than last year, right? So I tried to find what it is. Ladder was clean, so were the light niches BUT ....My pool has an oveflow cannal and reservoir. The cannal is covered with white hard stripes of plastic that connect to one another in the middle. Every one has a male and female connecting "point' and so you can connect as many as you like in a row, plus they can curve if you like, so I end up having about 30 of these/1 metre for a total of over 1000 to cover the entire pool. As soon as the rain season starts I stop using the overflow canal and function of the pool bacause all of the dirty rain water from around the pool used to enter the canal due to improper alignment and end up in the pool. So I always thought these plastic cover of the canal where clean or so they seemed....until i dismantled some. There was algae inside the connections!! I started to clean every single one of them in a different location of my yard with a pressure washer and rinse them in a dilute chlorine solution. It took me a month 3hours/day but i finally finished a couple of weeks ago! (they cost 25$/meter I saved 1000$:p) I also scrubbed the inside of the canal thoroughly with dilute chlorine water and the inside of the overflow reservoir after emptying it.
I then refilled my reservoir , added cya and salt to it (its about 5000liter) and went back to normal overflowing operation.
So i thought I had it all figured out and I could reduce the SWG but....no I couldn't. It still needed 50% to keep FC at 5. Plus I never saw a cc of 0. I decided to boost the FC .
(with TF 100)
Baseline
ph 7,4 (Hayward Ez pH ayto regulated and corectly calibrated )
FC 5
CC 0,5
CH 350
Cya 60
TA 120 (the overflow canal aerates the water as it falls in the reservoir like a little waterfall)
Salt 3200
borate 10-15?
temp 28 celcius

I added 10000ml of 12% chlorine I had left from last year yesterday at 11am. Had the SWG at 100% pump 24/24. Half an hour later FC 9 (!!! it really lost its power since last year it should have gone to FC 20) , CC0,5
We then went to the sea to swim.....hoping the SWG would do its job (last year it managed to boost FC by 5 in a matter of 6 hours)
4pm FC 10 CC 0,5 nothing added
5pm FC 11 CC 0,5 nothing added
6pm FC 12 CC 0,5 nothing added
7pm FC 12 CC 0 !!!nothing added
8pm FC 12 CC 0 nothing added
10pm FC 12 CC 0 nothing added
11pm FC 12 CC 0 nothing added turned SWG off and crossed fingers


This morning FC 11 CC 0,5.

Questions;
1. Do you think I am missing something here?
2. Is my OCLT valid with a FC of 12 and is it a pass?
3. What could be using up this extra chlorine so I cant dial down my SWG (bather load is exactly the same last year and this year)? Last year 100% ALWAYS brought the FC up in a matter of 6 hours this year it is hardly keeping up:(
4. Should I SLAM just in case? (my family will hate me if i do this right now) remember my water is better than ever!
 
Did you check your SWCG plates to see if they need cleaning? Perhaps their output has dropped due to calcium carbonate scaling though normally with your numbers (slightly negative CSI and pH controlled) that should be minimal. You could turn off your SWCG and manually chlorinate with a known quantity and concentration of chlorinating liquid or bleach to see if the chlorine demand is consistent with what you expect for the output from the SWCG. You can also measure the FC from water taken from a return when the SWCG is on and see if the FC is as high as expected given the flow rate.
 
The cell is brand new. I changed it 2 weeks ago after 21/2 years. It has not changed the demand for the 50% setting. My old cell had very little scale (if none) build up and I never had to clean it in those 21/2 years. I am sure something is eating up my chlorine...Oh and my returns are all (5 of them) at the bottom of the pool so I cannot measure the FC there. HOWEVER I forgot to mention that I changed the pumpr of my pool this spring since my old one broke down. I did install a smaller one to keep my electricity bills down since I can still get a 8h turnover with the new one. The flow did go down by about 20% but I calculated this and have been working the pump 4 more hours a day than last year. Is this it?
 
Well, if anyone can diagnose a chlorine issue, it's CG above. But just my 2-cents worth ... You appear to be sure you're losing FC more than normal. We should be confident in knowing that's from one of two places - the sun or algae/organic material. Your OCLT was right on the line for passing. It passed, but was close. You started at midnight, but did you let go about 8 hours before checking the next morning? Adequate time is important. Minimum 6 hours, 8 or so ideal. And because your CYA is at about 60 (SLAM FC being 24) "maybe" the FC of 12 used for your OCLT was just a hair too low to give you a good picture (% of FC loss). But those are just some OCLT thoughts.

As CG stated, you could always go manual for a day or two and record your FC loss. That, coupled with another OCLT should give you some solid answers. And if you have to SLAM, it's not the end of swimming. You can still enjoy the water up to your SLAM/Shock level FC. Best of luck!
 
Thank you Splash. I will bring my FC to shock level tomorrow keep it there all day if I can with the SWG (or extra bleach) so practically SLAMing the pool and then try another OCLT. I have a feeling that it might not just be the new pump ....Should it be enough to kill anything lurking?
 
Keeping the FC up is probably a good plan for now. But don't try to do it with your SWG. It will just exhaust your system. When we SLAM, we recommend relying solely on bleach. It's quick, easy, and will save some service life on your SWG cells. :) After the OCLT, when everything is resolved, then turn your SWG back on and try adjusting its performance.
 
I came up with this doing a little research in the forum pages:liqued bleach in your hot tub
In that discussion chem geek specifically states:
"The bigger concern is with the bacteria that causes "hot tub itch", Pseudomonas aeruginosa, which needs around 4 ppm FC with 20 ppm CYA to kill (this is a conservative estimate)."
This is definetely concerning. If it is true then with the target FCs from the pool calculator pseudomonas wont feel a thing and the regular weekly shock dose we all heard about from our parents or the pool industry might make a lot of sence.
If you take into account that l have never SLAMed my pool fot two years now, but last year I had an outbreak of swimmer ear (more than half the people that went in had one) with the water crystal clear and perfectly balanced EXCEPT the 0,5 CC, and FC always at target levels for my CYA... I think that from now on I am going to slam once a week at least during july and august and keep my FC 50% above target or as much so as I can go to 0 CC

I have also found this article:
Pool Tip #55: Pseudomonas Aeruginosa Aquatic Consulting Services
It specifically states that we need to shock at 0,2 ppm CC and not 0,5 as per pool school in order to eradicate pseudomonas.

"Shock spas daily and pools at least weekly, or as needed if combined available chlorine levels exceed 0.2 ppm. Make sure that you allow enough time for the chlorine to reach the breakpoint. Double check your calculations to make sure the correct amount of chlorine is being used. Inject the chlorine into the return lines using a chemical metering pump, or install a slurry feed bucket so that large amounts of chemicals can be poured into the return lines. Do not hand feed or pour the chlorine directly into the pools. Do not remove high levels of chlorine from the water with sodium thiosulfate. Let chlorine levels return to normal gradually after the breakpoint has been achieved"

Any ideas folks??
 
Last edited:
I have edited that post with the following later information:

[EDIT] As shown in this later post Pseudomonas aeruginosa is killed by low levels of chlorine where 0.1 ppm FC with no CYA equivalent, so a 10% FC/CYA ratio kills 99.9% in 1.5 minutes. [END-EDIT] It is specifically this paper that gave such kill times:

As expected, chlorine was the most effective among the three antimicrobial agents against planktonic cells, as shown in Fig. 1a. It required a CT value of 0.05 mg·min/liter to inactivate 1 log (90%; CT90) of the planktonic cells with chlorine. On the other hand, the CT90 of the biofilm cells in chlorine was more than 300 mg·min/liter (Fig. ​1b).
Click to expand...

A 3-log (99.9%) reduction would have a CT value roughly 3 times higher so 0.15 which means that 0.1 ppm FC would take 1.5 minutes for such a kill. The key is to kill the bacteria before they are able to form biofilms since they are then more resistant to chlorine. This paper shows that maintaining chlorine levels can prevent biofilm formation. The paper showed 5.53-log reductions in bacteria down to 3.7 cfu/cm2 on coupons of various materials. The paper did show that superchlorination for 16 hours reduced bacteria to 1 cfu/cm2 which was the limit of detection, but the counts are so low in either case to not be of concern. More relevant was that in sand filters the 6.70-log reduction got down to 219 cfu/g whereas 16 hour superchlorination got down to 1.3 cfu/g so had a more noticeable effect. These experiments had high bather-load simulations equivalent to 1 bather per 350 gallons per day. Note that active chlorine levels were high at 1-3 ppm FC with no CYA and that superchlorination was to 10 ppm FC again with no CYA.

The reason I initially thought that bacteria needed a higher chlorine level was that earlier sources I looked at didn't distinguish between planktonic bacteria and biofilms and this bacteria readily forms biofilms, but the bacteria can be killed fairly quickly before it forms such biofilms.

Swimmer's ear does not always come from Pseudomonas aeurginosa which is a common soil bacteria (and is found in unchlorinated water), but rather is from other bacteria already in your ear and as I've noted in posts linking to the Mayo Clinic and other sites, swimmer's ear comes from water in the ear. While pools with high bacterial counts would make swimmer's ear even more likely or worse, one can get it from being in pure water with no bacteria. Again, it is from having too much water stay in your ear allowing bacteria to proliferate and if the skin in the ear is damaged then it is more likely for such bacteria to penetrate the skin.

As for why you had more than half the people get it last year, were they all playing with water guns or in a way where they got more water in the ear than usual? That is what others have reported on the forum. Again, if you've been properly maintaining the FC/CYA level at all times, you should be fine (though read my last paragraph in this post regarding possible biofilms in your sand filter). You will note from searching about swimmer's ear on the forum that it is not that common and when it occurs it is most likely with the same people -- some in a family get it more readily than others -- and is due to the shape of their ears and how much they retain water and they get it from multiple water sources (not just pools). Again, read the Mayo Clinic article on Swimmer's Ear including the easiest way to prevent it in Prevention using a 50/50 mixture of rubbing alcohol and white vinegar.

Now if you had a group of people all get swimmer's ear from the same period of time swimming and they weren't doing anything to get water more significantly in their ears like using water spray toys then maybe you did have some bacteria in your pool, but we get nearly half a million visitors to TFP per month with over 90,000 members half of whom have posted and over many years we've never had that kind of situation occur. Every swimmer's ear incident is instead explained by the sensitivity of the individual (who gets it from other water play areas as well) or their activity or being in unchlorinated water (i.e. not in a properly maintained pool).

As for CC, you need to test using a 25 ml water sample because you will likely find that your CC is in fact <= 0.2 ppm. So you don't really have 0.5 ppm CC since one drop is the limit of resolution in the Taylor test. If you do have higher CC, then expose your pool to sunlight more -- maybe the pool is covered for too long. Pools need to breathe at least once a week and be exposed to sunlight so that the UV can break down some chorine into hydroxyl radicals that can break down bather waste that is otherwise slow-to-oxidize by chlorine alone. Furthermore, that article talks about shocking to lower CC in the same article it talks about Pseudomonas but they are not related. CC has nothing to do with bacteria. CC is mostly from chlorine combined with bather waste (ammonia and urea) and the context in that article is for higher bather-loads as found in commercial/public pools. Residential pools, especially outdoors, almost always have very low CC. The reason we talk about 0.5 ppm is only because the 10 ml water sample size is used where the one drop resolution of the test represents 0.5 ppm. Actual CC is almost always <= 0.2 ppm.

Actual Pseudomonas aeurginosa most commonly shows up in spas as hot tub itch/rash. I kept track of a series of such reported incidents on a hot tub forum in this post where the most common reasons seemed to be the use of "alternative" non-chlorine methods and the long-term use of Dichlor after 2 and especially 3 months where CYA buildup would have occurred. That's when I modified the Dichlor-then-bleach method that had already prevented such CYA buildup but had caused pH rise in a spa that the person didn't control so they got scale. So I not only had the TA lowered but added 50 ppm Borates as a requirement to help control pH rise to prevent scaling. Note that in hot tubs it is much more common for people to let the chlorine level get too low since the volume of water is small and the bather-load much higher than in residential pools.

If you want to elevate the chlorine level (SLAM or any other elevated level) periodically you can certainly do that since it won't hurt except to oxidize things faster (pool covers, etc.), but it should not be necessary and will of course be extra cost. If we start seeing more than just one report of bacterial problems in pools not having any regular shocking, then we can reconsider the current recommendation to simply maintain the minimum FC/CYA ratio. However, it's been 18 years if we count the time when Ben Powell started The PoolForum and PoolSolutions and maintaining the FC/CYA and not doing regular shocking has been the approach in all that time.

What I would suggest, since you have a sand filter, is that perhaps that was the source of the bacterial problem, if there was one in the pool. As noted in the paper, bacterial growth in sand filters even in maintained chlorinated environments may be an issue (at least in the conditions of high bather-load). This is most certainly the case in high bather-load commercial/public pools. Though you could superchlorinate as one technique (though with CYA in the water you won't be able to superchlorinate anywhere near as high as done in the paper), another approach would be to occasionally clean your sand filter of biofilm using Ahh-Some or since you are in Greece and may not be able to get that product you should be able to get AquaFinesse Pool. Why don't you take a look at your sand filter now to see if you have any clumping of the filter sand that not only could result in channeling, but may indicate the presence of biofilms. Again, we don't see this occur very often (i.e. clumping and channeling in sand filters in residential pools), but maybe that happened in your case.
 
Thank you for the reply. I will try to keep my FC at the higher end of poolcalcurator range so as to have 0 CCs just in case, considering my pool gets 12 hours of direct sunlight and it is very hot this time of year. I did already do it actually starting from yesterday. As far as otitis is concerned...pseudomonas is part of the canals flora. It proliferates when your ear gets a lot of hot alkaline water if you are in any pool considering the normal canal has a ph of 5.4 to keep germs at bay. If you add to that a pool water full of pseudomonas you only make it a lot easier for people predisposed to the condition to get it. Last year the same people who were in my pool everyday all af June got swimmers ear in end July with no diferent swimming habits and with no diference in water balance except for the 0.5 CC.
My filter has new sand (I changed it last year when I had an issue with fine dirt because it was of unkniwn age to me after buying the house) and I did check it after your reccomendation to find it perfectly fine at least the high layers I checjed. Pressure rises as expected as well. Could I just in case empty pool water and fill the filter manually with dilute (say1to 5l bleach and let it in for 12 hours before backwashing?
I think the sourse of my peoblem was the dirty overflow canal grits. They are extremelly difficult to keep clean and are a source of dirt and pseudomonas finding its way constantly in the pool.
Pseudomonas by the way is a germ that gets easily resistant to a lot of antibiotics but I dont know if it can get resistant to low leveks of chlorine.... There are studies that isolated pseudomonas from pools and spas which was already resistant to heavy antibioticshttp://www.ncbi.nlm.nih.gov/pmc/articles/PMC3084478/
 

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I think you answered your own original question. If you've got an overflow canal that tends to lose chlorine (i.e. not well circulated) such that bacteria can form extensive biofilms (does it feel slimy?) then once biofilms form chlorine isn't going to kill such bacteria. Even doing a SLAM won't help because the CYA in the water has the SLAM level only be equivalent to 0.6 ppm FC with no CYA. Even a yellow/mustard SLAM level is only equivalent to 1.4 ppm FC with no CYA.

I think emptying the pool is pretty extreme and using chlorine alone while effective if you do it concentrated is still not the best way to deal with it. The bacteria are not likely in the bulk pool water but rather on surfaces (unless they get sloughed off). If you have this as a regular issue, you might be better off 1) specifically superchlorinating the area of the problem and most especially brushing/wiping surfaces, so the overflow canal area and 2) using a strong surfactant product that inhibits biofilms (i.e. Ahh-Some or AquaFinesse). As the article you linked to noted, "Swimming pools and hot tubs have even more complex piping systems than sinks and showers, thus increasing the difficulty of cleaning." Note, however, that this study looked at indoor pools and hot tubs, not outdoor ones, and also looked at high bather-load situations (one hot tub was residential, but the other hot tubs and all pools were competition or public recreation). The positive samples for bacteria were swabs of surfaces as opposed to the bulk water and that's consistent with planktonic bacteria being killed by chlorine while biofilms are not readily addressed by chlorine. Note that this is one of the reasons we recommend regular brushing of pool surfaces. Of course, one can't get inside piping or other hard-to-reach surfaces.
 
Ok . Now I have CC 0 after just boosting the SGW for a couple of days. My readings are
FC 9
CC 0
TA 110
ph 7.4 (try to lower alkalinity)
CH 340
CYA 70
29 Celcius

I did another test from the overflow reservoir water at the same time and interestingly the results were
FC 6
CC 0,5
all the rest the same.

So I now know where exactly my problem is. I will remove all of the grills of the canal at the end of the season clean and decontaminate them somehow and install new tiles in the canal. Another problem is that my perimeter canal is not perfectly aligned so water does get stagnant in a couple of corners when nobody is swimming to force it to move. So after installing the new tiles and putting the decontaminated grills back I should be ok. The funny thing is that my pool water is perfect right now and was looking the same at the peak of the heat wave in end July except for the 0,5 CC. Is it possible that bacteria can show up as CC? or the fact that the water was hotter than usual led to the outbreak of otitis I will never know.The next time I find CC I will take a sample to the hospital and run a microbiologic analysis just to be sure. I will try to keep the FC hifher when the pool water gets above 28 celcius
Question:
How can I decontaminate the grills to be 100% sure that everything is gone? Cleaning them has proved a real nightmare. Each one has 8 different surfaces!!
I am trying to find an economical way to replace them with stone or stainless steel grills which would be much easier to clean at the beggining of the swimming season and a sort of longrun solution since I cannot imagine myself cleaning and decontaminating 1000 little plastic grills every year!!! This is what I have :

pisina.jpg

444.jpg

This is what I am hoping to get: (last image)
 

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Gorgeous, but wow, lot of trench grid to clean ;)
I wonder if you just mixed a chlorine/water solution (eg 1:1) in a big spray pump (the kind you'd use for insecticide) and just went around the perimeter with that once a week if it would reduce any issues without aging to rip the grids apart. You'd wan to spray right into the trough and not get overspray...
 
If you find your CYA dips over time, maybe you can just put a 1" puck at all the high points in the trough so when water went through there it grabbed some extra chlorine. I know direct contact with a puck can damage plastic and other things, so this isn't a real recommendation but some food for thought.
 
CC is a measure of chlorine combined with ammonia (inorganic chloramines of monochloramine, dichloramine, nitrogen trichloride) or organics (mostly chlorourea). It usually comes from higher bather-load or from not having sunlight on the pool. In most outdoor residential pools, the UV in sunlight breaks down chlorine into hydroxyl radicals that are very short-lived but powerful oxidizers that may react with organics such as urea that are otherwise slow to react with chlorine. If this does not happen, then urea can build up and chlorourea will show up as CC that seems persistent and hard to get rid of. This is primarily a problem in indoor pools without UV systems and in high bather-load commercial/public pools.

If you have a pool party, then the temporary higher bather load can result in more inorganic chloramines that temporarily have the CC higher, but chlorine will oxidize the monochloramine over a period of hours.

As for bacteria, they usually don't result in CC unless you have a lot of them usually in a sand filter in which case they can not only produce CC but produce the most irritating kind, nitrogen trichloride, under locally acidic conditions. This more often occurs in higher bather load pools with sand filters that aren't specifically cleaned to prevent biofilms.

In your situation, it's possible that biofilms formed in the grate area but as to whether they created CC or not is an open question. It is not necessary to find CC and have a bacteria problem. You could get sloughed off biofilm and not measure CC so I wouldn't use an absence of CC as an indicator that your grates were clean and I wouldn't necessarily conclude that the CC meant you had a problem, especially if 0.5 ppm is the lowest measurement in your test. It may very well be that your CC is actually <= 0.2 ppm, but to know that you'd need to use a 25 ml water sample size in a FAS-DPD chlorine test.
 
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