Sizing for the SWG??

[m61376]

Ugh- getting conflicting information. I was told by one person that the rated gallonage is assuming you are running the filter 24 hours a day, and by another that it relates just to the gallonage of the pool and roughly 8 hours a day is adequate for sufficient salt generation. The latter contractor recommended the Hayward SWG, which I see only has the largest unit rated at 40,000 gallons, and it generates up to 1.45 pounds of chlorine a day.

I'm not really sure what that all means though- is the 1.45 pounds over a 24 hour period, or within a shorter filter run cycle? And how much chlorine is needed per 10,000 gallons?

 

[swimcmp]

Not familiar with Haywards ratings but I believe that is over a 24 hr period. Chlorine demand will vary on a day to day basis.

 

[bobodaclown]

I have a CPSC48 on my 17K pool. My pump runs 5 hours in winter to 10 hours in summer. The output given is for a 24 hour period. (pump running). If you run your pump less than 24 hours you'll need to get a bigger unit. Make sure the unit you purchase is adjustable. I've been happy with my Compupool CPSC48. Did the install myself it's pretty easy if you're somewhat a DIYer.
2 to 3 times the size of your pool. That's my recommendation. This is one of those cases it's better to have too much than not enough.

 

[Bama Rambler]

We normally recommend sizing a SWCG 1½ to 3 times the pool size. All the mfg's that I'm aware of rate their units in what it produces over 24 hours. If you sized one exactly to your pool size and you matched the scenario that the mfg uses, you'd have to run your pump 24 hours a day and the unit would have to be on 100%.

 

[m61376]

Are all the 40,000 gallon units, for example, rated to produce the same amount of chlorine? For example, the Hayward one produces 1.45 pounds/24 hour. If my pool generally uses 6-8 3" tabs a week, then isn't it only using 4 pounds of chlorine max a week (since the tabs are about half a pound, but not pure chlorine). In which case running the pump for 9 hours a day should produce the same amount of chlorine (again assuming that the tabs were 100% chlorine)?

Since theoretically we should be able to keep the chlorine level a little lower in a SWG pool, then wouldn't that sized unit be adequate given my calculations, even though the pool is close to the 40,000 gallon size? Or am I missing something here?

I know the AquaRite is rated to produce the 1.45 pounds/24 hours; are competitor units rated at the same production levels?

Thanks for your help in trying to understand all this!!

 

[JasonLion]

Are all the 40,000 gallon units, for example, rated to produce the same amount of chlorine?

No. The various manufacturers have somewhat different notions of how much chlorine is suitable for 40,000 gallons. They are mostly fairly close together, though one or two of the off brands are significantly smaller than the others.

Remember that the SWG needs to be sized for your max chlorine usage during the sunniest and hottest days of the year, not for your average usage.

Generally speaking, nearly any SWG rated for 40,000 gallons will be just fine for a 40,000 gallon pool in the North East, and none of them will be sufficient for a 40,000 gallon pool in the desert South West. It depends on how much direct sunlight your pool gets, how warm the water gets, and how many people swim for how many hours on a regular basis.

On the other hand, getting an oversized unit saves you money in the long run (on most brands anyway), and it helps you deal with the occasional special situation when you need extra chlorine.

 

[bobodaclown]

JL is right on. Bather load is a big thing to take into account. We had a party and pets in the pool (extreme load) I just added liquid bleach to bring the FC level up. I could of increased the pump run time, but at times liquid chlorine (bleach) is easier and quicker to add to bring the FC level up in those rare instances. It's about pool management. Having a SWCG is much easier than lugging jugs of chlorine every day or so.

 

[m61376]

I live in NY (Long Island) so I guess that explains some of the differences from what I've been told and what I'm reading, since chlorine demand is obviously lower than in the South.

Can this simply be supplemented by a granular shock as well, or just liquid bleach, for the occasional heavy bather load or pool trashing due to a storm?

 

[bobodaclown]

Supplement using liquid bleach