SWG in commercial pool code

[holden94]

In NC public pool code the following requirement is listed:

"...have a generator that is capable of feeding a chlorine dosage equivalent to four and one-half (4.5) pounds of available chlorine per day for each ten thousand (10,000) gallons of pool capacity"

Can someone tell me how that is expressed in ppm output?

 

[jblizzle]

Hmmm ... that seems to be ridiculously over-sized unless I am not doing a conversion correctly. The SWG I have is listed for a 40k pool and only creates up to 1.45 pounds chlorine in a day.

Using the poolcalulator and entering 4.5 pounds chlorine gas (72 oz) for 10k gallons that would be equivalent to generating 54 ppm in a day ... so clearly something does not make sense.

Also, SWGs are generally not rated as ppm output, so I am not exactly sure what you are trying to figure out.

 

[Strannik]

i think the fact that there is such requirement doesn't mean it has to work at a 100% all the time.

it just has to be capable of it in case you need to increase chlorine levels quickly for some reason (kid having an accident?).

it does seem grossly oversized though. i'd normally recommend a model producing 8 pounds a day for a 40k commercial pool.

 

[linen]

This being a commercial pool, it has the potential for much higher bather load than a typical residential pool, hence the higher requirement than the T-15 cell can produce...how high is high enough, I have no idea. I will give the node to strannik and others who would know.

 

[Poolsean]

In NC public pool code the following requirement is listed:

"...have a generator that is capable of feeding a chlorine dosage equivalent to four and one-half (4.5) pounds of available chlorine per day for each ten thousand (10,000) gallons of pool capacity"

Can someone tell me how that is expressed in ppm output?

Holden94,

I would be very interested in a link where you found this information, as I just looked through the NC public pool code and could not find this. I can only find that 1 ppm is the minimum Chlorine maintained in the pool. Perhaps for a specific county?
http://ehs.ncpublichealth.com/docs/rule ... -25-12.pdf

However, this is normal for public pools codes, where they define a dosage rate in lbs/day. 4.5 lbs/day is quite high. Florida comes out to 1 lb/day per 10,000 gallons. I've always used 1 lbs/day per 10,000 gallons for NC (which is also South Carolina regulations). California and AZ are 3 lbs/day per 10,000 gallons. Iowa varies, depending if it's indoor or outdoor (5lbs/day outdoor or 2 lbs/day indoor, per 10,000 gallons).

You'll find that NSF50 certification have gone to showing the approved dosage output of salt chlorine generators in lbs/day or grams/hr rates.
http://nsf.org/certified/pools/Listings ... it1=SEARCH

 

[chem geek]

4.5 pounds chlorine gas equivalent per day in 10,000 gallons is 54 ppm FC, but that's over 24 hours so the rate is 2.25 ppm FC per hour or 3 ounces of chlorine gas equivalent per hour. Every person-hour of bather load is roughly 4 grams (0.14 ounces) of chlorine gas equivalent so they are asking for the ability to handle a peak load of 3/0.14 = 21 bathers or 476 gallons per bather.

Typical pool codes define maximum bather-load in a pool with large deck areas (more than twice the area of the pool) as 8 sq.ft. per bather in shallow areas or 10 sq.ft. per bather in deeper areas. Splitting 50/50 this says that 10,000/9 = 1111 gallons per bather is required.

So the 476 gallons per bather has to assume chlorine demand from more than "clean" bathers. Urinating children or significant biofilms in sand filters can have much higher chlorine demand such that 8-10 grams per bather-hour is not unheard of, but is indicative of a poorly managed pool.