oversiging cell for longer life?

[Brock]

I am thinking of going to a salt water system. My wife is concerned about the CL in our poolroom. Most of the time it is not a problem and keep it about 1-2 ppm. I understand with a SWG I can keep it closer to .5 (I revise that to 1ish) and should have less off gassing and greatly reduce the need to shock, which is really a pain indoors.

My first problem is my pool size. I was by our builder it was 15k, but since it is 4 feet to 10 feet and 13x27. According to Michael’s very cool little program (thanks!) I have an 18,500 gallon pool and attached 600 gallon hot tub. I guess I can just call it 20k to be safe?

So should I get a cell for 20k or a larger cell? Is it bad to oversize? The thing I thought was odd was that the larger auto pilots units have longer warranties so why not get a larger one that wouldn't run as much and lasts longer?

I have a compool controller if that matters and wired it all myself, so the electrical side isn't an issue for me.

Thoughts? Suggestions?

[duraleigh]

Hi, Brock,

Yes, bigger will last longer.

Now, I am concerned you are getting it for the wrong reason. I'm not an indoor pool guy but I think the principles of Cl are the same.

I don't think you should have any smell in your pool unless you have chloramines. That means you shock to get rid of them but, by shocking, the smell goes away.

Are you shocking because you have CC or just as a maintenance item? I have yet to shock my (outdoor) pool in two summers. Is the smell what you are calling "off-gassing". Again, I think that smell is because you've got CC and have not maintained an adequate Cl level to keep them at bay.

Lastly, I doubt you'll get much encouragement from the SWC guys to run @ .5ppm Cl......that's VERY low. But it sounds like you may be approaching the issue from the wrong direction,

Brock, I could be full of it because I know nothing about indoor pools but I'm comfortable with how and why Cl acts like it does.

The smart guys will be along to give better advice than me. I sure am curious to find out the answers, tho.:)

Dave S.

[KurtV]

I'm sure that Dave is right that other smart guys like him will weigh in, but until they get here...Won't the lack of sunlight eating your Cl significantly reduce the demand for it (likewise the lack of organic matter falling into your pool)? You can probably go smaller and still get longer cell life than you would in an outdoor application.

[waste]

Dave, thanks for the intro, but I'm not sure I qualify as 'one of the smart guys' :p .

Brock, I can only tell you from the 2 pools I've done that are indoor with SWGs, the problem lies in the other direction, the smallest SWG unit produes too much chlorine. The problem, as I've figured it, lies in the fact that, being inside, the pool gets neither the UV exposure, nor 'organics' that usually (continuously) enter an outdoor pool, which in turn, make up a substantial portion of the 'chlorine demand'. Even at the lowest setting (5% for the Goldline/Hayward units we install), 4 hours/ day of pump time results in ~5ppm chlorine - a lot more than is necessary - of course there's no cya in an indoor pool.
As I understand it, cell life is determined by run time (and voltage running through it ?) and @ 5% for 4 hrs/ day, I think these cells might be almost a 'lifetime' purchase. It does depend on pool usage though, if you had the entire 'BOYS SWEATING TEAM' in your indoor pool, actively practicing in your pool for 5 hours a day 7 days a week, you might have to turn the output up to 10% and run the pump for 6 hours/ day :) .
Poolsean, or Mark from Watermaid, may have more info on low cl output from their units (that just doesn't sound right), um... whether their companies products are capable of producing less chlorine for a noncommercial, indoor pool.

[Brock]

Yes you’re all correct. I shouldn't have said .5 for CL (I was just thinking out loud) (I changed it in the first post), but I would like to maintain the pool more regularly at whatever level it is. I typically only have to shock about 4 times a year and it is almost always after we have leaky little swimmers or add bay water with algae and other fun living small things. We test the water before every swim and add 8 oz after, but that isn't always enough to catch it and a day or so later we have a murky pool. We don't have the CL smell at all under normal situations, but when we shock the pool we have to keep the cover off and then it smells pretty good for a week or so even with the exhaust on high and I hate to have people over then. Almost everyone who comes over is amazed that the house or even the poolroom doesn't smell like CL.

And yes being indoors we have very little organic things introduced other then bather load to the pool. Right now I use just liquid CL at 12% and use about 1 gallon every other week. Not sure if that is a lot or not.

Do the units cycle on and off or are they variable do they sense the CL and adjust or is it a timed thing as Waste suggested?

Our problem, as with many pools, we have our family in at least every other day (1 year old baby boy, 2.5 year old girl and 4 year old boy). Then we have 16 nieces and nephews who are over at least twice a month and both my wife and I have kids pool parties for the people we work with. So something that just maintains the water under these odd loads would be wonderful. Maybe I am thinking they do more then they really do?

[waste]

Brock, I had meant to mention in my original post, the advice I give all pool owners - when there are people using the pool, the pump should be running, reguardless as to where you are in the timers cycle. Sorry for the oversight.

[Poolsean]

Hello Brock,

I'm one to always recommend getting the largest size cell you can afford. In your case, an indoor pool does not consume as much chlorine as an outdoor pool. In either case, the Pool Pilot has some programmability to accomodate the overchlorination conditions that has already been mentioned in previous posts. In other words, you can program the Digital to only generate chlorine for a preprogrammed number of hours per day, if so desired.

Your question regarding whether the cell cycles on/off throughout the day, always on (variable power to the cell), activated for a specific amount of time, or always fully on would depend on the manufacturer of the system you are considering. This will affect the way your pump run time is operated, or not...again, depending on the system you select.

What has been already pointed out is that you do not have a UV degradation issue with your indoor pool, so any chlorine generated will be consumed by your family using the pool. Every other day is probably more than normal so I'd say that you will get a pretty good consumption of chlorine. Is your pool heated as well? That too will consume some chlorine.

From past experience, an indoor pool with very little usage tends to result in overchlorination, due to the chlorine not being consumed and the salt chlorinator generating every day. You asked about if the system was capable of "sense the CL and adjust". This gets to ORP technology...which I am fortunate to be the only salt generator company that offers this as a Total Control system for residential pools. However, you can get an ORP controller as a separate component and add it on with just about any salt system you select. By using the ORP controlled system, it would not matter on cell size, bather loads, chlorine demands, etc...the system will generate chlorine only when needed, otherwise the cell will be in the rest mode (off).

I noticed that you mentioned that you add "BAY WATER WITH ALGAE AND OTHER FUN LIVING SMALL THINGS"....gulp...um.... please explain.

You mention that currently you add one gallon every other week. One pound of chlorine generated by a salt system is equal to one gallon of 12% bleach. This means that your chlorine demand would be about 1/2 lb per week. This is very low chlorine demand.
Your salt system would not have to generate too much chlorine. So basically, the advice given about utilizing the smallest cell and still getting excellent cell life is correct. I would love for you to reap the benefits of longer warranty and cell life by going to a large cell. You can still do this without concern with the Pool Pilot (as I mentioned that we can program the unit for lower chlorine outputs). I cannot speak for the other manufacturers.
The call is up to you.

Hope this helps,

[Brock]

Waste great advice, we do run the pump for a minimum of 4 (typically I just spin it up to 12 hours) hours after anyone has been swimming. I added a spring wind timer that overrides the compool setting and we run it every time. I also run the pump in low speed for 15 hours a day, maybe overkill but I feel better and with the two speed pump in low speed it isn’t bad electricity wise.

Sean yes our pool is heated, to much I think, but my wife won’t go in it otherwise, so it is about 88F.

Yes we top off our pool with water from the bay of Green Bay an inlet off Lake Michigan. Our well water is about 1800 ppm TDS, very hard and has a lot of metals in it. The bay is about 50 ppm TDS and is quite soft, but being a large body of water has its share of algae and other small living things. We do filter it though four 5 micron filters before it hits the pool and shock the heck out of it when I add any significant amount. I have been refilling the pool every other year and this is a refill year. I would get the water cleaned up and balanced before I ever installed or turned on a salt system.

And yes this helps a lot, my understanding of how this all work is much better.