Automated FC Readings

[HA99]

Apologies for a long post; hopefully this has enough background / detail to answer most questions.

First, just wanted to say how great TFP is. I'm a new hot tub owner and after months of frustration with the frog system and cloudy water, I found TFP in January and followed the dichlor - chlorine method. My TA and pH have been rock solid and a couple of ounces of chlorine each day have kept the water crystal clear. I'm amazed every time I open the cover.

Now I'm looking for an automated solution to take FC readings that will ultimately be used to automate chlorine dosing so that I can go away for more than a couple of days. I have a home automation system and have found several people who have used probes and sensors to take readings that trigger automations to control dosing pumps. There are a ton of resources for doing this with hydroponics, such as for pH but not for FC. Some have suggested calculating FC based on ORP, pH and temp. I reached out to Atlas Scientific about using their sensors and asked what the calculation would be. Despite selling a kit specifically marketed to pool owners that comes with ORP, pH and temp sensors, I was told that such a calculation doesn't exist, but ORP can be used as an indicator. Several posts here go into details on that, but I've struggled to find a direct answer to my question among all the technical details.

Here's what I want to do:
* Use continually submerged and hidden sensors (i.e. pH, ORP and temp) to take automated readings
* Based on the readings, calculate an appropriate amount of chlorine to dose using an automated dosing pump
* Sufficient accuracy to allow ~10 days away. While home, I will manually test the water regularly
* I'd prefer a DIY solution

If there really is no way to accurately determine FC levels (automated, without an expensive FC probe), my second approach would be to find a static amount of chlorine to add each day that would keep it in the 3-5ppm level without use. It's covered, under a deck so no UV concerns. Then when we use it, I would manually add more chlorine as needed.

I would love to know if anyone is calculating dosing based on probe readings. I know this capability exists as there are a few products on the market, such as Sutro. Can anyone help me get over the hurdle?

Thanks in advance!

-Brian

 

[thrystan]

Apologies for a long post; hopefully this has enough background / detail to answer most questions.

First, just wanted to say how great TFP is. I'm a new hot tub owner and after months of frustration with the frog system and cloudy water, I found TFP in January and followed the dichlor - chlorine method. My TA and pH have been rock solid and a couple of ounces of chlorine each day have kept the water crystal clear. I'm amazed every time I open the cover.

Now I'm looking for an automated solution to take FC readings that will ultimately be used to automate chlorine dosing so that I can go away for more than a couple of days. I have a home automation system and have found several people who have used probes and sensors to take readings that trigger automations to control dosing pumps. There are a ton of resources for doing this with hydroponics, such as for pH but not for FC. Some have suggested calculating FC based on ORP, pH and temp. I reached out to Atlas Scientific about using their sensors and asked what the calculation would be. Despite selling a kit specifically marketed to pool owners that comes with ORP, pH and temp sensors, I was told that such a calculation doesn't exist, but ORP can be used as an indicator. Several posts here go into details on that, but I've struggled to find a direct answer to my question among all the technical details.

Here's what I want to do:
* Use continually submerged and hidden sensors (i.e. pH, ORP and temp) to take automated readings
* Based on the readings, calculate an appropriate amount of chlorine to dose using an automated dosing pump
* Sufficient accuracy to allow ~10 days away. While home, I will manually test the water regularly
* I'd prefer a DIY solution

If there really is no way to accurately determine FC levels (automated, without an expensive FC probe), my second approach would be to find a static amount of chlorine to add each day that would keep it in the 3-5ppm level without use. It's covered, under a deck so no UV concerns. Then when we use it, I would manually add more chlorine as needed.

I would love to know if anyone is calculating dosing based on probe readings. I know this capability exists as there are a few products on the market, such as Sutro. Can anyone help me get over the hurdle?

Thanks in advance!

-Brian

I use the second method to add chlorine. I set a given amount to add each day and have a program that adds part of the amount every hour if the pump is running. I have an ORP sensor, but I just use it as an indicator to tell me if I'm way out of whack. If the ORP reading is way too high I will lower the daily dose and if it's too low I'll raise the dose. If no one is using the pool your daily dose should be fairly consistent, obviously it will go up with longer sunnier days and down with shorter cloudier days. But that shouldn't be something that requires adjusting the daily dose more frequently than weekly. And if you have remote vpn access to your home network you can make those adjustments.
Last summer I was gone for about 4 months and when I got home there was a slight green tint in a couple of shaded sections of the wall that don't get great water flow. This was before I got the ORP sensor so I didn't have any feedback at all about the chlorine level. I'll be away for a month this summer and I'll see how it goes with the feedback. Since no one will be using the pool I'm not concerned if the chlorine level is perfect, just if it's approximately right, preferably on the high side.

 

[thrystan]

I use the second method to add chlorine. I set a given amount to add each day and have a program that adds part of the amount every hour if the pump is running. I have an ORP sensor, but I just use it as an indicator to tell me if I'm way out of whack. If the ORP reading is way too high I will lower the daily dose and if it's too low I'll raise the dose. If no one is using the pool your daily dose should be fairly consistent, obviously it will go up with longer sunnier days and down with shorter cloudier days. But that shouldn't be something that requires adjusting the daily dose more frequently than weekly. And if you have remote vpn access to your home network you can make those adjustments.
Last summer I was gone for about 4 months and when I got home there was a slight green tint in a couple of shaded sections of the wall that don't get great water flow. This was before I got the ORP sensor so I didn't have any feedback at all about the chlorine level. I'll be away for a month this summer and I'll see how it goes with the feedback. Since no one will be using the pool I'm not concerned if the chlorine level is perfect, just if it's approximately right, preferably on the high side.

I just noticed your talking about a hot tub not a pool, which might make things a bit easier since the amount of time needed to mix the chlorine will be much lower. For my 30,000 gallon pool it takes a while for added chlorine to affect the ORP reading.

 

[HA99]

I just noticed your talking about a hot tub not a pool, which might make things a bit easier since the amount of time needed to mix the chlorine will be much lower. For my 30,000 gallon pool it takes a while for added chlorine to affect the ORP reading.

Thanks for the reply. I just ordered the ORP and pH kits from Atlas. Looking forward to this next project!