commercial / public pool question

[cj133]

I chose this section because, I think this kind of is off the deep end.
Looking at a drawing and requirements for a small public pool I'm amazed at what it calls for as far as filtering etc.

Off the top of my head, it's something like 10' wide by 30' long, fairly shallow, like 4 feet deep and indoors.
It calls for four skimmers, multiple main drains and three 900 pound sand filters. four skimmers and 2700 pounds of sand for such a tiny pool that's inside? I'm really confused.

My next question is, they show an ozone generator and an oxygen concentrator and then some kind of mixing tank, then there's a salt chlorinator and some other equipment.
What is that all about?

I'm astonished at the equipment such a small pool has, but also genuinely curious why this is setup up the way it is.

 

[ajw22]

Those who develop the commercial pool requirement cannot predict bather load or quality of maintenance so it is all based on worst case assumptions to protect the public.

 

[JoyfulNoise]

Go to your local authority and look at the building requirements for public pools. There will likely be very strict rules on minimum flow rates and turnover as well as safety precautions for drains (large are split drains) to minimize water velocity into the drain so that entrapment cannot occur. Many states ban the use of cyanuric acid in public pools and so there typically has to be chlorine and a secondary oxidizer present to handle the bather waste. The mixing tanks are contact tanks used to ensure that the ozone that is generated has longer contact time with the water so that it can kill pathogens. The tank needs to be designed so that it can blow-off the ozone into an a appropriate venting system, usually with some form of ozone eliminator to control emissions.

Just be glad that these types of regulations aren't forced on to private residential pools or else most of us would be waiting to schedule the dump trucks to come in with the fill sand to pour into our pools ...

 

[cj133]

Go to your local authority and look at the building requirements for public pools. There will likely be very strict rules on minimum flow rates and turnover as well as safety precautions for drains (large are split drains) to minimize water velocity into the drain so that entrapment cannot occur. Many states ban the use of cyanuric acid in public pools and so there typically has to be chlorine and a secondary oxidizer present to handle the bather waste. The mixing tanks are contact tanks used to ensure that the ozone that is generated has longer contact time with the water so that it can kill pathogens. The tank needs to be designed so that it can blow-off the ozone into an a appropriate venting system, usually with some form of ozone eliminator to control emissions.

Just be glad that these types of regulations aren't forced on to private residential pools or else most of us would be waiting to schedule the dump trucks to come in with the fill sand to pour into our pools ...

What is the reason for banning CYA in some areas?
Also, is CYA necessary for an indoor pool? That had occurred to me as well, but the way you wrote your response leads me to believe chlorine stabilization isn't the only purpose?

Or is the indoor situation part of the problem CYA aside, because there's no sunlight to burnup the spent chlorine?

 

[JoyfulNoise]

What is the reason for banning CYA in some areas?
Also, is CYA necessary for an indoor pool? That had occurred to me as well, but the way you wrote your response leads me to believe chlorine stabilization isn't the only purpose?

Or is the indoor situation part of the problem CYA aside, because there's no sunlight to burnup the spent chlorine?

Somewhat of a long story but I'll try to summarize -

Why no CYA in commercial pool?

Because sometime public health officials are really not that smart ... There have been studies that showed when the CYA gets too high, the pathogen kill rates decrease and disease transmission goes up. Well, the "geniuses" in public health look at FC and CYA and they say - "Oh My Gosh!, CYA is soooo terrible, it decreases the effectiveness of chlorine .... WE MUST BAN IT!!!!" Well, what these "geniuses" forgot to do is to look at not FC, but HOCl concentration since HOCl is what kills pathogens. Lo and behold, if you keep the HOCl concentration up, the it doesn't matter what the CYA level is as pathogens will be killed .... EXACTLY what TFP teaches, ie, maintain the proper FC/CYA ratio (the FC/CYA ratio is just another way of holding the HOCl concentration constant). But, being Public Health "experts", they were not required to pass their chemistry classes to get their degrees and so .... there you have it - overreact to poorly designed studies and do stuid things ...

Is CYA only necessary for outdoor pools?

NO! CYA is primarily a chlorine buffer. Meaning, it holds most of the chlorine in reserve by bonding to it and only allows a small amount to exist as HOCl/OCl- (active chlorine). By acting as a buffer, it makes chlorinated water less harsh. Water with 1ppm FC and zero CYA has about 15X as much HOCl in it as water with 3ppm FC and 30ppm CYA. The water with 1FC and zero CYA will sting your eyes, create lots of nasty chloramines, and bleach your swim clothes. The water with 3ppm FC and 30ppm CYA will do none of that and it will be enjoyable to swim in.

So ABSOLUTELY YES, even indoor pools will benefit from CYA.

 

[Lake Placid]

Because sometime public health officials are really not that smart ...

Don’t get me started……develop a good relationship with your inspector and I’ve seen them not even walk into the pump room but just ask “Everything good down there? Yes sir…..Ok you pass”.

Or you have the inspector that wants to make a name for himself and instructs you to place equipment in a location that it isn’t designed for……and is called out by the manufacturer to be installed in the opposite way to function properly…..but the inspector wants it right there in that spot. Even his supervisor (who is an engineer) when called agrees with your objections, but instructs you to place it in the wrong location…..to get the operating permit.

I’ve even had inspectors tell me “I don’t know, I’m just the middle man” when out of their depth trying to justify a BS policy or regulation.

Brass tax, it’s bureaucracy at its finest.

 

[cj133]

Somewhat of a long story but I'll try to summarize -

Why no CYA in commercial pool?

Because sometime public health officials are really not that smart ... There have been studies that showed when the CYA gets too high, the pathogen kill rates decrease and disease transmission goes up. Well, the "geniuses" in public health look at FC and CYA and they say - "Oh My Gosh!, CYA is soooo terrible, it decreases the effectiveness of chlorine .... WE MUST BAN IT!!!!" Well, what these "geniuses" forgot to do is to look at not FC, but HOCl concentration since HOCl is what kills pathogens. Lo and behold, if you keep the HOCl concentration up, the it doesn't matter what the CYA level is as pathogens will be killed .... EXACTLY what TFP teaches, ie, maintain the proper FC/CYA ratio (the FC/CYA ratio is just another way of holding the HOCl concentration constant). But, being Public Health "experts", they were not required to pass their chemistry classes to get their degrees and so .... there you have it - overreact to poorly designed studies and do stuid things ...

Is CYA only necessary for outdoor pools?

NO! CYA is primarily a chlorine buffer. Meaning, it holds most of the chlorine in reserve by bonding to it and only allows a small amount to exist as HOCl/OCl- (active chlorine). By acting as a buffer, it makes chlorinated water less harsh. Water with 1ppm FC and zero CYA has about 15X as much HOCl in it as water with 3ppm FC and 30ppm CYA. The water with 1FC and zero CYA will sting your eyes, create lots of nasty chloramines, and bleach your swim clothes. The water with 3ppm FC and 30ppm CYA will do none of that and it will be enjoyable to swim in.

So ABSOLUTELY YES, even indoor pools will benefit from CYA.

Ok stupid question. And this is kind of off track, but I've been curious for a while and my boss literally just asked me because his CYA ended up too high due to using pucks..

What's the difference between a CYA of 30, 60, 80, 100 etc? What happens as you raise that level, as long as you keep your FC high enough for it?
What would the real world difference between a CYA of 30 and FC of 5 and a CYA of 100 and a FC of 12 be? Would the higher CYA allow longer intervals between adding chlorine? Is there a point where FC simply becomes ineffective no matter how high it is?

 

[JoyfulNoise]

In an outdoor pool, higher levels of CYA can produce greater shielding from UV loss. Even though some of the information out there states that UV loss is consistent for a specific FC/CYA ratio, the reality of it is a bit more complex and we do see greater UV shielding at higher CYA. The problem with high CYA is that if you get into trouble, ie algae, then it is a lot harder to fix because the amount of chlorine needed becomes unreasonable.

So there is a balance in outdoor pools - find the lowest acceptable CYA level that gives you a reasonable amount of chlorine loss per day (2-3ppm per day is usually doable), and then target your FC for a 7.5% ratio.

For indoor pools, UV loss really isn’t a concern so CYA just needs to be around 30ppm to make the water comfortable to swim in.