Thinking of a DIY system for ORP, pH and SWG

[koffie]

My pool is controlled with a homebuild system for turning on pump, SWG, heatpump, lights and measuring temperatures.
It is all working perfectly, but I want to take the next step : measure pH and chlorine. The Atlas Scientific sensors (pH and ORP) seem to be good sensors for this setup.

I have zero CYA in my pool, and as I understand this would be the best for ORP meassurements. My SWG cell is capable of producing 25 gram chlorine gas, raising my FC with 0.6
If I would read the ORP frequent (during pumphours), I should be able to correct my FC by turning the cell on or off, correct? My SWG is set to 100% and is only turned on during pumphours according to a schedule, you could say the SQG is independent of pumphours.

The ORP sensor can handle up to 100 psi pressure, bu I'm not sure if it needs to be submerged all the time? The pH sensor (as far as I'm aware of) should be submerged to prevent dry out. To prevent dry out of at least the pH probe, I would make some lowering in a running pipe so there will allways be water in that part of plumbing?

Any ideas, thoughts? Am I totally wrong in my plans?

 

[jblizzle]

I think ORP has more issues than just the CYA level.
Your SWG is not going to last nearly as long as it could if you would add the recommended CYA.
And I have no idea how you could ALWAYS maintain adequate FC levels with no CYA in the water since the sun will destroy it faster than the SWG can generate it.

 

[koffie]

This is my second year with the pool, first year working with TFTestkit. Learned about CYA this year opening the pool. Since I have only SWG I had no CYA in th pool last year. I still have to find a good resource to buy CYA in my country. We have very less poolshops in here, and most are all about buckets of pugs. All the chemicals you can easily buy in USA are more hard (and expensive) to get over here.

When I would add CYA, would this effect ORP readings ? When starting with a ORP sensor, it would be good to compare testkit results with the ORP readings and get value for my specific setup.

 

[jblizzle]

Have you searched the forum for discussions about ORP sensors? Not much good to say about them.: Here are almost 1000 threads with the key work "ORP"
ORP site:[url]www.troublefreepool.com - Google Search[/url]

I am sure you can come up with other keywords to limit the search

You could use Trichlor or Dichlor to slowly add the stabilizer with additional chlorine.

 

[Patrick_B]

It will effect the readings and you can try to get them to level out mV versus test results, but it's very troublesome at best.

 

[Tepelus]

Do not waste your time with the ORP sensor. Readings are influenced by many factors. Ph has a big impact on the sensor output and is difficult to have a control loop with both PH and ORP sensor. You may have separate loops, but they should not interfere with each other. CYA can be added to the pool water by using pucks for some time. Not difficult to calculate how much you need. I do not use a SWG, but I know that Ph will rise and has to be adjusted often. Have a Ph control loop to keep Ph close to 7.4 and many of your worries will go away.

 

[Bama Rambler]

I'm going off the beaten path and say that if you have zero CYA (or even up to 20ppm) and can regulate the pH fairly stable (should be fairly easy), you should be able to control the swcg fairly well with ORP. I'd put the pH adjustment after the ORP so it wouldn't interfere with it.

You will need to adjust the ORP target based on a comparison with the FAS-DPD test, and you'll still need to run the test often to make sure the probe isn't drifting for some reason.

If you have the resources and the know how, I say go for it. Somebody has to be the guinea pig. :0

 

[koffie]

My pH is very stable for this season. It stays at 7.2 every test, haven't put any pH plus or minus in the pool this year. I could start with the pH project. Insert a probe, monitor behaviour and after that see if I need/can make a autofeeder for liquid pH (minus or/and plus). When that is doen, I can start thinking and looking if I want to go to ORP sensor.