CC - Wont go down!

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HarrisonHRG

Active member
Sep 18, 2024
38
Hampshire, UK
HI Folks,

Got an interesting one (and please id only appreciate any constructive feedback not the "This isnt the forum for that" bla bla - Please :) )

We have a persistent, High CC reading, of around 3-4PPM. I've done a SLAM for over 4 days with even double the PPM FC on the CYA/FC SLAM level. but still no change on the CC. - water is crystal clear.

We are using Sodium Hypochlorite @ 15% commercial.

Pool is 75m3, salt cell & VERY heavily bathed in, we have had at a rough calculation over 6000 persons in the pool within the last 9 months. (yes, i know that's a commercial pool level, but the TFP method has still been king over any commerical supplier!)

Test results:
PH; 7.4
CC: 3.6PPM
FC: 4.8PPM (just allowed to reduce post SLAM)
CYA: 15 (indoor pool, used as a moderator to protect the bather against HOCL as we can run up to 6-8PPM FC to maintain the supply)
TA: 165
SALT: 3000PPM.
TEMP: 30-31 Deg C.
CAH: 110

Ive seen alot of other posts online about MPS, would a non chlorine shock assist in us reducing our static CC levels? Any other suggestions?

what effect does MPS have on the bather?

Thanks folks appreciate your time in advance.

H
 
A high use indoor commercial pool needs a system like UV to help manage CCs.

You also need a lot of daily dilution to replace the contaminated water.

Organic CCs are more persistent than inorganic CCs.

I recommend a properly sized Commercial UV system.
 
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Not surprised at all you’re seeing persistent CC levels with that kind of bather load. @JamesW is correct, you are operating at commercial pool levels of use. The bather waste alone (sweat, urine, feces, etc) is going to create a constant load of organics that the hypochlorite will react with. Much of it will turn into persistent CCs rather than more volatile chloramines. In fact, if you are seeing high levels of chloramines on your chlorine testing then you likely have even higher levels of THM’s and DBP’s that your tests aren’t sensitive to.

You need a very large freshwater exchange and the installation of a commercial grade UV system, preferably with a contact/mixing tank. A mixing tank with Ozone would help too but there are a lot of expensive environmental controls that need to be in place to operate that safely.

MPS will only be a bandaid fix and the MPS itself will show up as CCs on your testing so it will be difficult to see if it’s having any effect or not.
 
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HarrisonHRG said:
Pool is 75m3, salt cell & VERY heavily bathed in, we have had at a rough calculation over 6000 persons in the pool within the last 9 months.
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6,000 people in a 20,000 gallon pool is very high use.

Can you explain the nature of the bather load?

Is this a hotel, gym or what?

How much "Chlorine" smell is there?

How much dilution do you get?

What is the water clarity?
 
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To add to the others commentary what are you using for air exchanges for the pool area? Indoor pools without proper exhaust/outside air exchanges can suffer from high CC because the offgassing of CC has nowhere to exhaust to.
 
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PoolStored said:
Clean your test vial with rubbing alcohol and retest FC and CC. Let us know results.
Use a 10mL sample and each drop is .5 FC/CC. Will save reagent.
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We are currently using a PalinTest 6 kit, DPD reagent with a Photometer, the kit recommended to us on here is solely in the USA and the struggle is a +£300 kit… but cleaning it is a very good suggestion with IPA as I haven’t done that, it gets a scrub and dunk in pool water lol!
JamesW said:
6,000 people in a 20,000 gallon pool is very high use.

Can you explain the nature of the bather load?

Is this a hotel, gym or what?

How much "Chlorine" smell is there?

How much dilution do you get?

What is the water clarity?
Click to expand...
Sure - we are a private home swimming pool but allow locals to use the pool & pay by the hour. It’s a domestic pool which we have oversized the chlorinator & filter for this reason.

Chlorine smell is actually minimal, sometimes we have a “busy” period with up to 150 people in the pool over 12hrs, in which there is a mild chlorine smell but the bather is unaffected, we have received no complaints to water quality nor “over chlorination“ as swimmers tend to call it (Chloramines)

Dilution is not huge but more is done naturally by the deposition of water out of the pool and sides and back flushing the filter, I’d say 3-5m3 a week?

Clarity is crystal clear!!! - that’s the irony and part of the problem, the owner of the pool just goes “ah, it’s clear, we are getting no complaints and our chlorine levels are sanitary” (we also have ORP readings live to check for sanitation as a guide) - which is part of the problem..

But I’m just trying to make sure we are doing everything to ensure the maximum comfort to our swimmers & protection of our liner etc.
Lake Placid said:
To add to the others commentary what are you using for air exchanges for the pool area? Indoor pools without proper exhaust/outside air exchanges can suffer from high CC because the offgassing of CC has nowhere to exhaust to.
Click to expand...
Every night we open the doors slightly, and leave the cover 50% off to allow off gas, especially during a SLAM after a busy period. We do notice a reduction in CC after the Slam, but it never seems to reduce to a level that we class as “normal” hence why I believe we are in Perisitent CC’s and trying to figure out how to get them out..

Thanks to everyone for their feedback so far, I will do some digging into commercial UV. Does this same UV also reduce levels of FC as well as CC?
 
PoolStored said:
You can get the kit for +£125.

Click to expand...
We Would go through the standard taylor kit in like 3 weeks... we do multiple chlorine tests a day usually, we get 250 tests for the palintest system for around £18.

when i got a quote from the pool shop linked to this forum to the UK, the price, including the extra re-agents was well over £300 including import tax.. Definitely not worth it but still cheaper than the amazon kit :(

Its a shame its only produced in the states and we cant get a reliable source over here..

H
 
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HarrisonHRG said:
We are currently using a PalinTest 6 kit, DPD reagent with a Photometer, the kit recommended to us on here is solely in the USA and the struggle is a +£300 kit
Click to expand...
Palintest is a fine machine for daily use if you maintain it. I can’t recall if that model uses the XF reagents for up to 10 ppm chlorine readings or not. That’s a downside to a palintest, the lack of high range readings. Makes it difficult to perform a proper SLAM. When was the last time you sent it in for calibration? Do you have check standards so you can field verify its accuracy? If not I’d recommend you get some. The orp system is a conversation for a different day lol
 

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What you have is a public/commercial pool … doesn’t matter if it’s in a backyard or a building, it’s being operated as public pool and the bather load is extreme.

One way to reduce the CCs is to meter/limit the use. All commercial water facilities here in the US have regulations regarding the number of allowed bathers in a pool and require that pools be emptied of swimmers for a period of time, typically around an hour give or take, several times per day. This “downtime” period allows the operator to perform the legally required testing of the water and gives a chance for the system to filter and disinfect the water. Recreational water illness (RWI) is a big deal and diseases can transmit quite rapidly in pool water. If a commercial facility cannot get their CC to come down, they are usually required to close the pool until it is remediated either by chemical treatment or by freshwater exchange.

I’d you intend to keep operating the pool at such high bather levels, you’re going to need to implement tighter controls over the chemistry and use of the pool. I don’t know anything about personal injury litigation in the UK but here in the US a setup like yours is an expensive lawsuit waiting to happen.

Consider UV treatment and regular water exchanges as well as more restrictive scheduling and more frequent downtime through out the day. It’s really the only options you have.
 
Lake Placid said:
Palintest is a fine machine for daily use if you maintain it. I can’t recall if that model uses the XF reagents for up to 10 ppm chlorine readings or not. That’s a downside to a palintest, the lack of high range readings. Makes it difficult to perform a proper SLAM. When was the last time you sent it in for calibration? Do you have check standards so you can field verify its accuracy? If not I’d recommend you get some. The orp system is a conversation for a different day lol
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Yeah we have the HR DPD kit with up to 10PPM. its still within calibration age as they recommend every year and we have had the kit for 8 months or so, so when it is recommended will get some check standards or send it off for a calibration.

Agreed on ORP, we do NOT use it as a gospel, but it definitely gives you a good ballpark indicator on sanitation level in the pool, if it decreases, we notice very much so.

JoyfulNoise said:
What you have is a public/commercial pool … doesn’t matter if it’s in a backyard or a building, it’s being operated as public pool and the bather load is extreme.

One way to reduce the CCs is to meter/limit the use. All commercial water facilities here in the US have regulations regarding the number of allowed bathers in a pool and require that pools be emptied of swimmers for a period of time, typically around an hour give or take, several times per day. This “downtime” period allows the operator to perform the legally required testing of the water and gives a chance for the system to filter and disinfect the water. Recreational water illness (RWI) is a big deal and diseases can transmit quite rapidly in pool water. If a commercial facility cannot get their CC to come down, they are usually required to close the pool until it is remediated either by chemical treatment or by freshwater exchange.

I’d you intend to keep operating the pool at such high bather levels, you’re going to need to implement tighter controls over the chemistry and use of the pool. I don’t know anything about personal injury litigation in the UK but here in the US a setup like yours is an expensive lawsuit waiting to happen.

Consider UV treatment and regular water exchanges as well as more restrictive scheduling and more frequent downtime through out the day. It’s really the only options you have.
Click to expand...
We test daily, monitoring the PH and ORP automatically by the Zodiac Chlorinator to our phones, but always test daily, most days twice a day.

Our daily bather load according to UK regulations is 120. we usually have on a busy day 50-70 persons in the pool max, so as long as we can maintain water clarity, a good sanitizer level & correct readings we are well within regulations. Instantaneous load we never allow more than 8 persons in the pool at once so we are well below the 25 limit for that....

I think UV is the way to go, our pool testing is working lovely, a good FC residual is always maintained and our low level of CYA is protecting the bathers (Thanks ChemGeek for the lovely CYA/HOCL graphs!) - We just need to work out how to outgas/remove our CC levels in which UV seems to be the solution.

Thanks
H
 
Get a commercial level UV system and use it when the CC levels get to 1.0, or higher.

UV also takes out FC, so I would only use it as needed.

Begin regular dilution based on bather load.
 
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