Why Should I Oversize My Salt Chlorine Generator?

System Capacity - A Primer

A shopper new to the world of saltwater pool equipment might find themselves considering a Salt Chlorinator with specifications stating a 20,000 gallon capacity for installation on their 20,000 gallon pool. This would be something to avoid! The industry quotes what are essentially “maximum capacities,” and we try to educate customers about why such a pairing is inadequate for proper pool sanitation before they make their final selection.

What’s the problem? Manufacturers determine system capacity based on how much water it could treat running at its highest levels at a maximum run time. So buying a salt system with a maximum capacity that is the actual size of your pool would be somewhat like buying a car that is ‘rated for Interstate highway speeds,’ but it can only maintain the speed limit with the accelerator pedal pressed all the way to the floor.

In other words, you as the pool owner want a chlorine generator with plenty of extra chlorination capacity. The rule of thumb for a properly-sized system is one with a manufacturer’s (maximum) capacity rating of at least 1 ¹/₂ times the pool size for moderate and colder climate zones and 2 times the pool size in hotter zones. So, by definition, a correctly-sized saltwater chlorine generator is oversized from the outset.

Let’s examine why you need to start out oversized and why it’s beneficial and wise to further oversize.

Required Oversizing

In order to achieve satisfactory results from your salt system, you need to be able to generate sufficient chlorine without having to run your equipment all the time at maximum chlorine output.

Pools experience changing needs for chlorine in the water. Higher temperatures, extended periods of unrelenting sunlight, weather events, and high bather load are prime examples of when and why you might need the ability to turn up the chlorine output.

Here too, the car metaphor holds up with these examples being equivalent to a car encountering hills, carrying or towing a heavy load, or needing to speed up to pass another vehicle.

In practical terms, following the rule of thumb of having a salt pool system with a maximum capacity of 1 ¹/₂ to 2 times your actual pool size means that under normal circumstances you should be able to run the salt chlorine generator at a moderate level within normal pool system run times. That way, you’ll be able to raise its output on demand in order to generate more chlorine should conditions require it.

Optional Oversizing (Or, Bigger Is Almost Always Better)

There are several benefits to having a larger salt system. The benefits include, longer salt cell lifespan, low extra cost, and higher output capacity.

Lifespan

Salt cells are able to generate a certain amount of chlorine over their lifespan. After they actively generate chlorine over many thousands of hours, the electrolytic cell becomes depleted. A simple way to think about it is this: a more powerful salt cell is able to produce more chlorine over its lifespan, and since your pool only needs a certain amount of chlorination, you’ll “use up” a bigger salt system more slowly than a smaller model.

To think about it in more depth, the “production hours” (time that the salt system is operating) are essentially prorated according to the output level, or chlorine production. A system can run at full power for 4 hours, half power for 8 hours, or quarter power for 16 hours and in all cases, it will use the same 4 hours of production time and generate the same chlorine.

So from this perspective, if you buy a salt system that is able to produce twice the chlorine, it can operate for the same hours at half the output or half the hours at the same output. Either way, the larger model's salt cell should last about proportionately longer than the smaller one!

(Incremental) Chlorine Cost

Larger capacity salt systems will cost incrementally less for the chlorine production and lifespan you receive. Considering two popular units*, the higher capacity model costs only 22% more for a unit that produces 45% more chlorine. Similarly, the larger capacity replacement salt cell costs only 17% more than the smaller unit and also produces 45% more chlorine. Since the larger cell will allow the same level of chlorination at a 30% lower output setting, it should also last roughly 30% longer, but without a 30% increase to the price tag.

Clearly, oversizing a system or a replacement cell will give you proportionately more life than the increased purchase price. While the actual numbers will vary from model to model, the same relationship holds true and will give you savings over the long term.

Be Prepared

Situations like a large pool party, an extended power outage, or a large storm can hit a pool pretty hard, creating a short term need for extra sanitation. In the aftermath of a storm, for example, a higher capacity salt system can give the pool a quicker, bigger boost in chlorine production and not spend as much time “catching up.” That shortened time can be vital in keeping the water balance from “turning.”

Of course, you can always supplement the salt system with a dose of chemical chlorine, but with all the benefits of owning a saltwater pool, do you really want to add chlorine, even just occasionally? Extra capacity to your salt system means you can turn up the output and quickly deal with a chlorine deficit by using the Superchlorinate setting, or manually turning the system up to 100% as needed.

Of course, you can always supplement the salt system with a dose of chemical chlorine, but with all the benefits of owning a saltwater pool, do you really want to add chlorine, even just occasionally? Extra capacity to your salt system means you can turn up the output and quickly deal with a chlorine deficit by using the Superchlorinate setting, or manually turning the system up to 100% as needed.

By the way, in spite of what some salt pool owners seem to think, the Superchlorinate function can’t turn up the output level beyond 100%.

Summary

As we discussed above, a correctly sized salt chlorinator is actually oversized from the outset. Upgrading to a higher capacity salt chlorine generator has big advantages. Since it is capable of producing extra chlorine when necessary, you can be confident that your system can handle most pool problems that might arise.

A larger system is typically more cost effective upfront, and upsizing also saves money by extending the system's lifespan more than the extra cost of the bigger device.

So, it truly is wise to oversize.

Frequently Asked Questions