ORP system help needed.

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J

jlsesler

Active member
Apr 23, 2019
26
Dallas
Hello,

I am having an ORP system installed in a couple of days. I have a decision to make, and I need some help. I am trying to decide if I want a 15gal liquid chlorine tank or a cal hypo erosion auto feeder. I understand some the pros and cons of the different chlorine types (liquid shelf life, cal hypo price and calcium accumulation, etc), but is one considered better than the other? Is it strictly a preference thing?

FYI, I have a new pool build that is about 33k gallons. I appreciate any advice.

Thanks,

Jason.
 
You’re going to find an ORP control system to be very difficult to manage. They are affected by more than just the free chlorine in the pool and will need regular calibration to keep them working properly. You’ll also need to keep your CYA level at 30ppm or less as CYA reduces the hypochlorous acid concentration which is primarily what the ORP is attempting to react to. A simple duty cycle based dosing system with a high quality test kit is a much lower hassle method. Trying to rely on probes to do your dosing will ultimately lead to more work, not less. I know in this age of digital/WiFi/hands-free/ask-Siri/home-automation everything that seems counter-intuitive, but residential pools are more easily managed by an attentive home owner, not a computer.

In your area, unless you plan to do a lot of seasonal water exchange, additional calcium is an unwanted chemical in your water. Liquid chlorine is a better choice but your system/setup will use a lot of it so you’ll have to plan for frequent tank refills.
 
Yikes! This is my 3rd pool that I have maintained myself (that last one was similar size). I figured there would some more involvement with winterizing and spring setup, but I was hoping to hear that these ORP systems are great and contribute to a lower maintenance pool overall. That's how the pool builder made it sound (they even gave it to me at cost as an incentive).

Anyway, thanks for the input on the liquid option. I was leaning that way.

Jason.
 
My last pool was salt. It was going pretty well until the first salt cell went out. My next 2 cells only lasted a little over a year each even though I keep a close eye on my overall chemistry (ph, chl, cya, alk, calcium, salt, etc). That's when I decided to abandon the salt pool, and the fact that I was looking to sell my house and didn't want to pay for another salt cell. :)

Anyway, it's too late to back out of the ORP system now. I have already paid for it, and it's unboxed and laying out on my patio (minus the chlorine feeder option). What type of weekly, monthly, yearly maintenance is required?
 
jlsesler said:
My last pool was salt. It was going pretty well until the first salt cell went out. My next 2 cells only lasted a little over a year each even though I keep a close eye on my overall chemistry (ph, chl, cya, alk, calcium, salt, etc). That's when I decided to abandon the salt pool, and the fact that I was looking to sell my house and didn't want to pay for another salt cell. :)

Anyway, it's too late to back out of the ORP system now. I have already paid for it, and it's unboxed and laying out on my patio (minus the chlorine feeder option). What type of weekly, monthly, yearly maintenance is required?
Click to expand...

What's been your experience with the ORP sensor thus far?
 
It started out very shaky for the first few months until we figured out that the ORP sensor that came with the system was bad. Once that was replaced, the system has been working flawlessly.

Up to this point, it is what I expected and hoped for. My pool is very low maintenance compared to the other pools I have owned. I check my chemistry about once per week (even less now that winter is coming), top off the chemical reservoirs occasionally, and empty the skimmer baskets about every 3-4 weeks. The in-floor cleaner and ORP system does a good job of keeping up with the daily/weekly maintenance even in the midst of swim season. So far, the ORP and PH sensors have been very accurate and consistent compared to my testing.

We will see how much of a pain it will be once I have to do the maintenance on it (tube and sensor replacement), but that is only needed every couple of years or so according to the manufacturer.

Jason.
 
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jlsesler said:
It started out very shaky for the first few months until we figured out that the ORP sensor that came with the system was bad. Once that was replaced, the system has been working flawlessly.

Up to this point, it is what I expected and hoped for. My pool is very low maintenance compared to the other pools I have owned. I check my chemistry about once per week (even less now that winter is coming), top off the chemical reservoirs occasionally, and empty the skimmer baskets about every 3-4 weeks. The in-floor cleaner and ORP system does a good job of keeping up with the daily/weekly maintenance even in the midst of swim season. So far, the ORP and PH sensors have been very accurate and consistent compared to my testing.

We will see how much of a pain it will be once I have to do the maintenance on it (tube and sensor replacement), but that is only needed every couple of years or so according to the manufacturer.

Jason.
Click to expand...

Interesting. If I may ask, what CYA level do you usually keep your pool at? I know that a few folks here have been talking about the ineffectiveness of ORP when the CYA is > 30. I assume that yours is kept really low?
 

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I am using a 15 gallon liquid feeder (with 12% liquid chlorine). During peak swim season, I refill it every 4-6 weeks. I am not exactly sure what you mean by availability. If you mean store availability, I have a local pool store that refills the containers I have at a good price.
 
Thanks for the info. Did you ever have ORP measured in your salt water pool? I cannot seem to get my ORP value above 500mv but I have only reduced the cya to about 50ppm. I guess the next step is to let it drop to about 20ppm. I know this goes against the grain of what is taught here but I want to know what my ”kill rate effectiveness” is in the pool.
 
No, I didn't try to measure it in my old salt pool. The high CYA is likely the reason why you aren't getting a good ORP value. From what I have read/experienced, there is very little benefit to having much over 20-30 ppm CYA. Above that, the sun protection benefit only increases marginally while the relative chlorine effectiveness drops more dramatically.
I initially had trouble getting my ORP above 600mv, but that was because that probe was bad.
 
jlsesler said:
.... From what I have read/experienced, there is very little benefit to having much over 20-30 ppm CYA. Above that, the sun protection benefit only increases marginally while the relative chlorine effectiveness drops more dramatically.
Click to expand...


This is not true. TFP has lots of user “data” over the years that shows quite clearly that CYA above 30ppm continues to add a protective effect all the way up to 100ppm or more. Richard Falk has even postulated several theories as to why that would be the case and has shown from data in peer reviewed journals that CYA likely absorbs UV radiation with a large enough extinction coefficient to adequately describe why people that use higher CYA levels have much lower FC loss rates than the basic chemistry would predict.

In my own SWG pool I keep my CYA up at 80-90 ppm with an FC around 3-5ppm and my FC loss rates, even in the intense summer months, are around 1-1.5 ppm per day. Any time my CYA drops below 70ppm, my FC loss rates go way up and my measured FC starts to noticeably fall. I see this effect every season because the degradation of CYA by UV here is enough that I lose around 15ppm/month. So usually by late July my FC is not keeping up and when I test CYA I am usually at 60ppm or less. Adding CYA back to 90ppm brings everything right back in line.
 
What you say is certainly conventional/traditional wisdom, but there are compelling arguments against maintaining higher CYA. I am sure there is data for both sides, but this article is interesting.
blog.orendatech.com

Minimal CYA | Pillar 4

Pillar 4 is Minimal Cyanuric Acid (CYA). CYA (aka Stabilizer or Conditioner) protects free chlorine from sunlight. Some CYA is good, but too much is bad.
blog.orendatech.com blog.orendatech.com

I have talked on the phone at length with the author of this article. He owns Orenda and a pool maintenance company. His company installed my pool equipment. He said he spent a lot of his 30+ year career "overstabilizing" pools and following traditional "range" chemistry. He has implemented his methods across hundreds (maybe thousands) of pools, and he swears by it. I always kept higher CYA too until he talked me into keeping it lower. It was a bit of a leap of faith for me, but I also adopted the other pillars he mentions. I can say that I have never had pool water this nice.
 
You are right, Orenda is applying the FC/CYA chart now, but in a way where they keep FC in the industry established range, which means that they have to keep CYA lower.

Richard's research and literature studies showed that the absolute chlorine loss by UV will be lower when keeping CYA higher. Reduced chlorine effectiveness needs to be compensated by increasing FC, keeping the FC-CYA ratio constant. The existing research showed that this is safe for swimmers and equipment - because CYA reduces the sanitation effectiveness of chlorine, it reduces it's harshness in the same way.

By keeping CYA and FC higher, pool owners have to buy and schlepp home less chlorine in total, and by sticking to the target rather than the minimum it gives enough safety margin to allow daily (or even less frequent once a pool's needs are understood) testing and chlorine adding.

With an ORP sensor and automatic chlorine feeder, you are in a different situation. The ORP sensor forces you to keep CYA below 30 anyway, but having a closed loop system with automated testing and feeding makes the lower FC range feasible, sudden bursts in chlorine need by a toddler pool party will be compensated for in time. But the absolute chlorine consumption will be higher due to higher UV-losses, period. If buying and schlepping home more chlorine is not considered a problem, then fine. There is a remaining risk that users become complacent and won't notice system errors until the pool turns green, but that's life, I guess.

But for manual, daily or less frequent, testing and dosing (including manually adjusted SWGs), I'd strongly recommend to keep CYA in the TFP recommended range, and stick to the required chlorine levels according to the FC/CYA chart.
 
Last edited:
Yes, I’ve seen all that before and the conclusions he draws miss the point or, at the very least, are wildly overstated (and he’s very much cherry-picking what Richard has said and what Richard thinks based on my conversations with Richard). I’m mobile now and can’t fully respond. I’ll get to it later. But he’s basically selling his “process” for pool care. It’s one of many out there. If you’re happy with the Orenda method, great. The TFP method is much simpler and while he may have built hundreds of pools, TFP has tens of thousands of subscribers that follow the methods here with flawless results as well.
 
I actually don't use Orenda pool care products, and I have no benefit in trying to sell their method. It seems to work at least for my case. It's arguable which method is simpler (TFP vs Orenda). I guess it just comes down to which one you are comfortable with. I personally think neither method is overly difficult, but I have been doing it for a long time. I think the Orenda method works well in conjunction with an ORP system (since you need to keep CYA low anyway).

Quick summary of Orenda method for those who don't know and are curious:
The Orenda method puts the primary emphasis on keeping LSI in balance. As long as LSI is in balance, some of the traditional ranges for alk, ph, calcium, etc can be stretched. Chlorine doesn't affect LSI, so it should be managed at traditional levels. They have a free app you can use to calculate it after inputting your test values.
 
Okay, I bit. Mainly due to my curiosity I guess (yea, I know all about what happens to the cat ;))
So downloaded the app and input my numbers.
Curious. To me there seems to be some relationship between CSI and LSI (aggressiveness of the water I guess)
Here is my LSI. You can also see the numbers (and my CSI) in my pool math logs.
2953FEAA-C356-4560-9B1D-D07CFD7CDF0E.png

I played around with the numbers to see what would keep the LSI closest to zero.
Mostly allowing my pH to rise to 8.2 puts the LSI at 0.08. This is curious to me because I swear, I am always fighting with pH it seems. It seems it just naturally wants to rise to the low 8's...
The other factor that has a significant and positive effect is allowing my TA to be a bit higher (100).
Reducing the TDS or Salt will also have a small positive effect (only about 0.01 LSI for every 100 ppm reduction).

Also, another factor that has a positive effect is allowing CYA to drop. I know why they propose that but I'm not about to let my CYA drop too low. I'm still staying with that method for now.

So I pose this question.
I'm thinking about allowing pH and TA to naturally climb up slightly (8.1/100 respectively). This certainly would make my water a little less aggressive as indicated by both this LSI chart and CSI in pool math. It would also keep my from playing "tug-a-war" with my pH I believe. @JoyfulNoise - Matt, thoughts on doing this (or anyone else that wants to weigh-in).
Thanks...
r.
Note: I realize that I should not focus too heavily on CSI. I get it! But I would prefer that it "live" a little more on the positive side rather on the negative side. I believe this may help me come out a little ahead in my pH "tug-a-war" game.
 

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