ORP Controllers - How to Predict Final Reading Without Waiting an Hour?

Hello everyone, I’ve just installed an ORP controller for my pool, but I’m getting impatient waiting for the number to settle. Is there any way to calculate what the ORP will be without waiting a full hour for it to stabilize? Thanks!

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In short, no. Look at the controller model to see if it includes a mixing delay. If it does, you can set the feeders to turn off for a few hours, allowing the water to balance and the ORP to stabilize at the desired level.

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@DiveDeepDreamer That’s a smart approach for when I need to add things like stabilizer and alkaline. Whenever I have to add alkaline, I need to adjust the pH set point to 8.0. If I don’t, the moment I add a bag of bicarbonate, the controller will activate the acid stenners and cancel out all the bicarbonate I just added.

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These are sense-and-dispense systems, but if a large group of 30 people jumps into the pool, it won’t be able to keep up. You’ll need another way to sanitize the water.

Before the weekend, if you have a tab feeder, fill it up with chlorine tablets as a backup method for sanitation.

Another option is to upgrade to a pump with a higher GPM, though this is a pricier solution and depends on your specific situation.

If your system has trouble handling low to moderate sanitation needs, it could be due to a clogged injector nozzle from calcium buildup, or you might need to backwash more frequently.

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@AquaAdventurer This is a 250k school pool with a large, older pump that I’m hoping gives out soon. I checked the injectors, and they seem fine, but I think the swim team may have caused the issue. The flow rate was fine, but my vacuum gauge showed low pressure, so I’ll definitely clean the filter on my next visit. It’s a DE filter with grids, so there’s no backwashing option.

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@Umbrielle Why on earth would a 250k commercial pool use DE filters?! I believe the issue here is the flow rate and higher bather load. Hopefully, they have the foresight to install sand filters before they waste their budget on weekly filter cleanings.

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@AquaAdventurer Haha, I’m not sure, but some maintain their flow rate for weeks. Only a few schools need them weekly or biweekly, and that’s usually just during the summer. These schools don’t invest any money, so expecting any major equipment upgrades is like chasing a lost cause.

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@Umbrielle Switching to a sand filter would save them money over time. It’s unfortunate, but congrats on earning money from the filter cleanings.

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If this is an ORP controller, why does it take an hour to stabilize? Shouldn’t it be operating continuously, making small, periodic micro-doses? Every controller of this type I’ve come across has a target set point, and many also include stroke and speed control for the pump.

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@BreaststrokeBuff When something goes wrong and you need to add things manually, you either have to estimate what the final number will be or wait a long time for it to settle if you want to avoid taking a chance with your guess.

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@Umbrielle There is a formula for this type of situation, but the outcome heavily relies on the specific characteristics of your water. For instance, bleach will behave quite differently in deionized water compared to a pool with high mineral content and significant green algae.

You could collect a water sample—preferably a larger one, around 5 gallons—and connect your probe to it (or use a different ORP meter, such as a handheld version if you have one). Add a small quantity of bleach until you achieve the desired result. Keep in mind that the contaminant affecting the ORP might need some time to react fully. I would recommend aiming for about 80-90% of your target level and letting the controller handle the rest.