Need to reduce chlorine generation below level possible with SJ-35 controls

[SteveinSC]

Hello everyone.

I installed a Circupool SJ-35 prior to last season. Works great, but it is way oversized for my pool. Even at the lowest setting it generates so much chlorine I can run the pump for only an hour or so daily or the chlorine level goes way too high. I would prefer to run the pump longer to get good particulate filtration.

My pool is small, approx. 7,000 gallons, and I intentionally oversized the generator (always good policy) but I may have messed up when I was offered an SJ-35 for pennies more than the SJ-25 I had planned on buying, and I went for it. Had an Intellichlor IC-40 on the pool before this and on low setting it generated the chlorine level I needed with the water circulating maybe 4-8 hours daily. I could simply adjust the timer to get a bit more or less chlorine as needed. I figured the SJ-35, intended for a similar sized pool (5k gallons less actually), would be perfect. Fact is it is generating far more chlorine than the IC-40 ever did, and I am having to monitor the water closely and cut the generator off for days sometimes just to keep things within an acceptable range. Lots more trouble and chlorine level fluctuates far more.

Only solution I can think of is to install a plumbing bypass around the cell I can adjust via a valve, so only part of the circulating water passes through the cell. Wondering if alternatively there's an in-line timer I could install between the power source (the timer) and the Circupool control box that would cut it off after a set time on each cycle. Plumbing mods probably easier, just wondering if I have a better option before tackling this.

The good news is the cell should last forever running along at idle speed.

 

[Bperry]

Hello everyone.

I installed a Circupool SJ-35 prior to last season. Works great, but it is way oversized for my pool. Even at the lowest setting it generates so much chlorine I can run the pump for only an hour or so daily or the chlorine level goes way too high. I would prefer to run the pump longer to get good particulate filtration.

My pool is small, approx. 7,000 gallons, and I intentionally oversized the generator (always good policy) but I may have messed up when I was offered an SJ-35 for pennies more than the SJ-25 I had planned on buying, and I went for it. Had an Intellichlor IC-40 on the pool before this and on low setting it generated the chlorine level I needed with the water circulating maybe 4-8 hours daily. I could simply adjust the timer to get a bit more or less chlorine as needed. I figured the SJ-35, intended for a similar sized pool (5k gallons less actually), would be perfect. Fact is it is generating far more chlorine than the IC-40 ever did, and I am having to monitor the water closely and cut the generator off for days sometimes just to keep things within an acceptable range. Lots more trouble and chlorine level fluctuates far more.

Only solution I can think of is to install a plumbing bypass around the cell I can adjust via a valve, so only part of the circulating water passes through the cell. Wondering if alternatively there's an in-line timer I could install between the power source (the timer) and the Circupool control box that would cut it off after a set time on each cycle. Plumbing mods probably easier, just wondering if I have a better option before tackling this.

The good news is the cell should last forever running along at idle speed.

Just put the cell on a timer and run it for only what you need. I used my old Intermatic timer for my Polaris to power the SWCG.

The plumbing plan is dangerous. The cell should never be powered unless there is water flowing through it. There’s a flow switch to help prevent it but if that switch fails, explosions happen otherwise.

Also just to make sure, what is your chlorine and CYA level. If you’re using pool store testing and faulty guidance it may be totally fine without any modifications.

 

[SteveinSC]

Appreciate the response. I don't see the plumbing solution as a problem. I would tee off for the bypass before the flow sensor, and of course also never bypass so much water that the cell is not always full. (It's a transparent cell, so easy to verify that). A separate timer I could see as a problem. If the pump timer fails and the chlorinator timer does not, the chlorinator would turn on with no flow. The flow sensor would cut the chlorinator off in that circumstance of course, but still....

I can see how an in-line timer between the main timer and the chlorinator, that cuts the chlorinator off after a set period during each cycle, could work well, but don't know what availability there is on that, and installation may be more trouble than it's worth compared to the plumbing.

Thanks again.

 

[Darin]

why not run a higher CYA?

 

[Bperry]

Appreciate the response. I don't see the plumbing solution as a problem. I would tee off for the bypass before the flow sensor, and of course also never bypass so much water that the cell is not always full. (It's a transparent cell, so easy to verify that). A separate timer I could see as a problem. If the pump timer fails and the chlorinator timer does not, the chlorinator would turn on with no flow. The flow sensor would cut the chlorinator off in that circumstance of course, but still....

I can see how an in-line timer between the main timer and the chlorinator, that cuts the chlorinator off after a set period during each cycle, could work well, but don't know what availability there is on that, and installation may be more trouble than it's worth compared to the plumbing.

Thanks again.

It’s not that the cell needs to be full of water, it needs to have water passing through it to capture the chlorine gas that’s made. And if water is passing through it enough to open the flow switch, chlorine gas will be made. When that happens, your water is being chlorinated just as much as it was before so you’re not reducing the amount of chlorine made, your just dissolving the same amount of gas in a smaller volume of water before it gets to the pool.

Most everyone sets it up so the SWCG is powered by the main pump power which prevents the SWCG being powered if you pump is not running. If you put a timer on the SWCG power feed in that scenario it’d be about perfect for you without any plumbing changes and no risk of the SWCG being on when the pump isn’t.

I actually run my pump 24x7 and the SWCG on a timer. I actually have them on separate breakers but I need to switch them over to be on the same one.

I’ve never heard of anyone doing the plumbing plan which may tell you something.

What is your chlorine level? If you have at least 30ppm CYA, your chlorine is safe to swim in all the way up to 12ppm.

 

[SteveinSC]

Running the pump 24-7 with the generator on a timer is a good idea and I appreciate that. A simple timer between the main timer and the chlorinator control would indeed be ideal if I could find one. Run the pump as long as I want via the main timer, but each time the chlorinator would cut off after an hour or however I have it set. Most folks complain of inadequate chlorine, and very few of too much, so I don't know if there's a secondary timer of that type made specifically for a pool system, but I could probably run something down. Haven't really looked yet. Just mulling different approaches.

I have no reservations about the plumbing option, provided I install the bypass tee upstream of the flow sensor for the cell, and partially close the bypass valve as needed to ensure adequate flow to the cell. I have heard of it being done for this issue, but can't recall where. No reason it wouldn't work that I see, especially as I run the pump on high these days so I can filter as much water as possible during the short-cycles I am using. Plenty of flow to work with.

And happily I can plumb and wire with the best of 'em.

CYA right down the middle, btw, from test strips. The chlorine level goes off-scale high to shock levels though, if I don't keep an eye on things. Would like to do something, just so I don't have to pay so much attention to it. The SJ-35 is proving to be a great unit. Certainly powerful. My only complaint is you can't set it to below 20%. Bottom line is I oversized too much.

Thanks for everyone's input.

 

[Donldson]

from test strips.

Wait, your results are from test strips??

 

[Newdude]

+1. How are you supposed to get a specific value from these ?





Each actual CYA value has an appropriate FC level which is equal for sanitation.



You're playing blind darts. Let's temporarily ignore the inaccuracies of test strips. They're just flat out too vague.

 

[Darin]

get a legitimate test kit and run higher CYA. It is easy.

 

[wireform]

besides a real pool test kit from one of these
Test Kits Compared

you may also benefit from something like
Amazon.com

 

[Bperry]

Running the pump 24-7 with the generator on a timer is a good idea and I appreciate that. A simple timer between the main timer and the chlorinator control would indeed be ideal if I could find one. Run the pump as long as I want via the main timer, but each time the chlorinator would cut off after an hour or however I have it set. Most folks complain of inadequate chlorine, and very few of too much, so I don't know if there's a secondary timer of that type made specifically for a pool system, but I could probably run something down. Haven't really looked yet. Just mulling different approaches.

I have no reservations about the plumbing option, provided I install the bypass tee upstream of the flow sensor for the cell, and partially close the bypass valve as needed to ensure adequate flow to the cell. I have heard of it being done for this issue, but can't recall where. No reason it wouldn't work that I see, especially as I run the pump on high these days so I can filter as much water as possible during the short-cycles I am using. Plenty of flow to work with.

And happily I can plumb and wire with the best of 'em.

CYA right down the middle, btw, from test strips. The chlorine level goes off-scale high to shock levels though, if I don't keep an eye on things. Would like to do something, just so I don't have to pay so much attention to it. The SJ-35 is proving to be a great unit. Certainly powerful. My only complaint is you can't set it to below 20%. Bottom line is I oversized too much.

Thanks for everyone's input.

The plumbing bypass won’t work the way you expect. Just trying to help you out.

The timer boxes are all over the place online and any most any pool store. Here’s one: Amazon.com

But if your data is from the test strips, beware that those are really really unreliable. Many frustrated people have come to TFP (including myself) after being bamboozeled by those things. There’s likely no need for any changes because your chlorine probably isn’t too high. Before doing anything consider getting a reliable test kit. Here’s a recommendation page:

Swimming Pool Test Kits Compared

What pool test kit should I buy? Why not use test strips? Our recommended test kits will pay for themselves in no time!

www.troublefreepool.com

 

[Dirk]

The bypass won't do anything at all for your chlorine overproduction. Don't even try it. The cell doesn't produce chlorine based on how much water is flowing through it, or how fast. It just produces all it can, and then none (on-off). That's it. It will put the exact same amount of chlorine into your pool whether the pump is running on high, or low, or the flow is 20 GPM or 50 GPM. You're on the wrong track with that idea.

You need a separate timer. And you need a flow switch for safety (I presume you already have that). And you need to wire the timer such that it's timer circuit voltage is always present (powered 100% of the time), so it'll keep time, and the line/load voltage must be routed from the same source that is powering the pump.

The point of all that is to make sure the timer is powered all the time.
And the SWG is powered only when ALL THREE conditions are met:
1. The main pump is powered.
2. There is an actual flow of water through the SWG.
3. The timer is in its "on" cycle.

If you need a diagram on how to wire it, holler. Meanwhile, please fill in your signature, so we know what we're dealing with. You'll get the best advice that way. For example, you'll get a different answer on how to wire the timer depending on if you have a single speed pump running on a timer, or if you have variable speed pump with an internal timer.

https://www.troublefreepool.com/account/signature

 

[Dirk]

Show us a picture of the timer you're currently using to govern your pump's runtime.

 

[RLP]

Water is lazy and will take the path of least resistance. Period.

It will not partially flow through a swcg and a bypass. It will be one or the other.

 

[Dirk]

Water is lazy and will take the path of least resistance. Period.

It will not partially flow through a swcg and a bypass. It will be one or the other.

If I may... that's not quite accurate. There are legitimate reasons to use a bypass on an SWG, and it will provide control over the amount of flow through it. For example, Pentair SWGs have an optimal flow rate range of 25-80GPM, and Pentair advises the use of a bypass if the flow rate is expected to be above 80. But that has nothing to do with the amount of chlorine that reaches the pool. I expect it has something to do with the delicate nature of the coatings on the plates inside the SWG.

You cannot use a bypass to adjust the chlorine output of an SWG.



You may be thinking of rivers and such. Water will seek the path of least resistance, unless there is some amount of back pressure. The pool is the back pressure, and once the water in the bypass hits that, it'll then flow into the SWG loop. I don't know all the physics involved, I just know that's how it works. @mas985 generally saves me when I get in over my head!

 

[SteveinSC]

Yep, you're right. At 50:50 flow I'd be chorinating one leg at twice the norm and merging it back with the unchlorinated bypass leg. No effect. The three conditions you note are essential. Only issue I have with a separate timer parallel to the pump timer is should the pump timer fail in the off position (but not trip the breaker feeding both) and the chlorinator turn on as scheduled via its timer with no flow from the pump, not a good thing. I do have an in-line flow sensor of course, but still. At any rate, yes a second timer.

Thanks

 

[SteveinSC]

With respect to pipe flow, I do understand that very well. You can most certainly bypass part of the flow around the chlorinator owing to the backpressure as Dirk says, and adjust the bypass valve to send probably as little as 40% through the cell. The way Dirk's drawn it, the majority of the flow will always be through the straight bypass section with the valve fully open, as there would be less resistance to flow than in the cell leg where there would be additional frictional losses and turbulent flow around the bends, along the edges of the chlorinator plates and from the bubbles. A partial bypass could definitely be done, it would just serve no purpose.

 

[Bperry]

Yep, you're right. At 50:50 flow I'd be chorinating one leg at twice the norm and merging it back with the unchlorinated bypass leg. No effect. The three conditions you note are essential. Only issue I have with a separate timer parallel to the pump timer is should the pump timer fail in the off position (but not trip the breaker feeding both) and the chlorinator turn on as scheduled via its timer with no flow from the pump, not a good thing. I do have an in-line flow sensor of course, but still. At any rate, yes a second timer.

Thanks

That’s why you don’t have two timers controlling two separate things. The pump timer controls the pump AND the feed for the SWCG timer. On the very slim chance the pump timer fails in the off position, there will be no power to the pump or the SWCG…no big deal. If the timer fails “ON” then the flow switch is the back up fail safe on the very slim chance the pump itself fails even when it’s powered on.

 

[SteveinSC]

I know what you're saying, but I have no separate SWCG timer. SWCG comes on with power to the pump and runs in 2 hour cycles or so until the pump turns off. I just want it to turn off after an hour and stay off until power to it goes off and comes back on. Simple. Just don't see such a thing out there.

 

[Bperry]

I know what you're saying, but I have no separate SWCG timer. SWCG comes on with power to the pump and runs in 2 hour cycles or so until the pump turns off. I just want it to turn off after an hour and stay off until power to it goes off and comes back on. Simple. Just don't see such a thing out there.

I provided an Amazon link up above. There are dozens of timer choices.