"Don't run SWG at 100%"...Why?

[PhotoEd]

Hi all,
I've seen mentioned several times that one should NOT run their SWG in the "Super Chlorinate/100%" mode.
But I can't recall why....anyone? My pool builder recommends hitting 100% once per week.

Thoughts?

 

[duraleigh]

The higher you run the SWG, the shorter the cell life.

You should disregard your builders advice for the 100% weekly. In a well maintained pool, there is no need.

If he's suggesting that to shock the pool, bleach is far better in it's effect and, in the long run, cheaper probably.

 

[Butterfly]

Hi PhotoEd,

Welcome to the forum

In addition to what Davd said, you might want to check out our Pool School article on How to Shock Your Pool.
The last paragraph has more info concerning SWGs....

There is also an article on Water Balance for SWGs.

 

[PhotoEd]

Thanks gang, I just wanted a straight answer why some people here said "Don't do it". I always saw the advice, just not the reasoning behind it. But I guessed correctly.

Agreed, I haven't had the need to shock a single time all summer...

 

[Strannik]

you can run it at 100%, just not 24/7

superchlorinate mode usually just puts it at 100% for 24 hours and then reverts back

 

[PhotoEd]

Correct. But why run it at 100% at all? Or back to the original question, why do folks on here say "don't do it at all"?

What is the benefit of running at 100%, if not to shock the pool?

 

[Strannik]

benefit is that you reduce your pump run time -> less money spent on electricity

i don't know why people say don't do it at all, it doesn't matter too much whether you run your SWG 8hrs/day at 100% or 16h/day at 50%, but it does matter when you run it 24/7 at 100%

the reason why most people advise not to use superchlorinate button is because it doesn't really do proper shocking, unless you have a huge unused capacity in your SWG (i.e you usually run it at 10% 4h/day)
and it does wear out the cell more

so it's cheaper, better and faster to just add some bleach when you want to shock

 

[frustratedpoolmom]

Or back to the original question, why do folks on here say "don't do it at all"?

Because bleach raises the chlorine level much faster than an SWG can in a short period of time, and if you ARE trying to shock, you likely won't reach shock level using the "boost" or "superchlorinate" feature at all. Also by not using it you will get more useful life out of the cell for daily chlorination.

 

[Pool Clown]

Super chlor is not the same as shock...
You cannot shock your pool with a Cl gen with much effectiveness. Like FPM said, the unit cannot make enough Cl fast enough. The way i understand it, A perfect shock would be for the water to be instantly very high on Cl. This really isn't possible, so we settle for very fast (the time it takes to pour it in), and you just can't get the speed with a Cl gen.

Did that make sense?

 

[PhotoEd]

It does.

 

[gregs]

What percentage / run time would offer the longest life for the cell with chemicals levels properly maintained for a swg? The minimum run time for the pump is to turn all the water in the pool once a day, so should you adjust the output to maintain 4ppm FC? Would there be any measurable benefit to running the pump longer with a lower percentage or vice versa? Does anyone know what goes bad in the cell?

 

[Strannik]

the precious metal coating on the plates wears out

 

[polyvue]

What percentage / run time would offer the longest life for the cell with chemicals levels properly maintained for a swg?

0% (OFF) would offer the longest life; perhaps the best answer is to operate the cell at the lowest possible setting for the shortest possible time period while still achieving minimum Free Chlorine for your pool. In a trouble-free pool (no algae, < .5 chloramines) that could mean 10% for an hour or two... or 75% for 8 hours. Lots of variables affect the optimal setting/hours of operation.

The minimum run time for the pump is to turn all the water in the pool once a day, so should you adjust the output to maintain 4ppm FC?

As you probably already know, 1 turnover per day is just a rule of thumb, not a commandment. Some pools need more than one turnover, a few can get by with less than 1 turnover. Many things have an impact on whether a given level of chlorine will work for your pool: Water temperature and balance, bather load (activity), water features, environment (eg. trees, pollen, dirt), use of solar cover, pump time, etc. Reference the guidelines in Recommended Levels in Pool School and then experiment with the time setting on your SWG until it works to maintain the FC that you wish to target. In general, aim for a chlorine level at least 5% of your CYA. (If CYA=50, Free Chlorine should be 2.5 ppm or more.)


Would there be any measurable benefit to running the pump longer with a lower percentage or vice versa?

The pump almost certainly uses more electricity than the SWG; therefore, there may be a cost advantage to increasing the % and reducing pump operation time. But (just to complicate your decision a bit!) there's also a potential benefit to doing the opposite -- extended pump time and lower SWG % -- because the pool water, while exposed to the same amount of chlorine in a 24 hr period, will have the chlorine being produced when it's most needed (say, during the day in sunlight.) That's why some pool owners schedule multiple run-times, to replenish chlorine that's been consumed by UV light or otherwise spent due to oxidation of contaminants brought in by swimmers.

Sorry, it's not really that complicated...

 

[gregs]

Thanks for the answers. I guessed there was some type of plating on the cell that is slowly consumed.

Its a new pool and I will start to adjust run times and % adjustment until I figure it out. Currently have been running 2- 4 hour times. 1 in the morning and 1 in the evening and the pool has been looking great. Have been using bleach up until this point and added salt yesterday so I can now turn the SWG on and see what happens!

 

[PaulR]

What percentage / run time would offer the longest life for the cell with chemicals levels properly maintained for a swg? The minimum run time for the pump is to turn all the water in the pool once a day, so should you adjust the output to maintain 4ppm FC? Would there be any measurable benefit to running the pump longer with a lower percentage or vice versa? Does anyone know what goes bad in the cell?

I've been told that cell life is measured in amp-hours, which you can think of as percentage times run-time. So, 10% for 10 hours and 50% for 2 hours are the same as far as cell lifetime goes.
--paulr

 

[gregs]

Does the cell produce continously whenever it is switched on? Or can it regulate the output. I was monitering my aquarite unit today and noticed times when I would go into the diagnostic menu and it would read 0.00 amps even though it was powered on and the generating light was on. Then I would come back a little later and it would have a 3-4 amp reading like it was working. It was set at about 50% power and had a salt reading of 3300. Is this normal? Can anyone explain how it works on a normal basis. Thanks

 

[polyvue]

Does the cell produce continously whenever it is switched on? Or can it regulate the output. I was monitering my aquarite unit today and noticed times when I would go into the diagnostic menu and it would read 0.00 amps even though it was powered on and the generating light was on. Then I would come back a little later and it would have a 3-4 amp reading like it was working. It was set at about 50% power and had a salt reading of 3300. Is this normal? Can anyone explain how it works on a normal basis. Thanks

Everything you describe sounds like normal operation. 50% power means that about half the time the cell will not be drawing electricity, so that explains the 0.00 amps. The salt reading is good. Just measure (test) the chlorine often in the first few weeks so you know if and when you need to adjust the control. On my pool (14K gallons, 3 hr pump time, cover in use), the chlorine level would quickly rise with a 50% setting, but yours may require it.

 

[Strannik]

Does the cell produce continously whenever it is switched on? Or can it regulate the output. I was monitering my aquarite unit today and noticed times when I would go into the diagnostic menu and it would read 0.00 amps even though it was powered on and the generating light was on. Then I would come back a little later and it would have a 3-4 amp reading like it was working. It was set at about 50% power and had a salt reading of 3300. Is this normal? Can anyone explain how it works on a normal basis. Thanks

it depends on a model

with some 50% output means that it's on 50% of the time within a given interval (say 5 mins)
with others it means that the cell actually gets 50% of the power, say 12V instead of 24V

 

[joshreis]

the precious metal coating on the plates wears out

This is correct. The salt cells have a coating of Ruthenium (sometimes Iridium too) on them and it wears off when the salt cell is generating. So naturally when it is at 100% it uses up more of its Ruthenium than if its at 20%.

 

[New2Me]

the precious metal coating on the plates wears out

So, the precious metal is what causes the reaction? I thought that it was the electrical magic, and that the coating just protected the base metal, and maybe "enhanced" the magic. After all, if the base metal is titanium, isn't that precious by itself? Most junior science electrolysis experiments call for the use of two pieces of metal(usually spoons), with out regard to content. How much performance increase does a coating give, or is it a plate life prolongation?