Questions about plumbing a ORP & Sensing Kit

[woodsage]

I'm going to be installing a Sense & Dispense system that has a SWG, a cartridge filter and Goldline ProLogic controller. My question is regarding the plumbing of the effluent tubing of the probe cell to the pool supply/suction side of the exisitng pool plumbing. The installation manual shows the effluent side of the probe cell installed before the pool pump. My existing pool plumbing will not allow me to install the flex tubing for the effluent port before the pump (I have a check valve and then valve actuators immediately before the pool pump and I do not want to replumb the suction side of the pool plumbing); I can however install the effluent tubing after the pump and before the filter.

Is the reasoning for installing the effluent tubing before the pump (suction side) is that the pump suction will pull/suck the water from the probe cell and then be filled with pool water from the influent tubing on the return (supply) side?

If I install the effluent tubing between the pump and filter does that mean that the probes will not be testing/monitoring a constantly changing flow of pool water but rather a stagnant pool sample?

I hope this all makes sense so thanx for everyone's help and input.

 

[JasonLion]

You won't get enough of a pressure difference across the filter to operate the sensor correctly. You need to find a way to connect it before the pump (or do something much more complicated).

 

[woodsage]

Jason -

There is a threaded plug at the bottom of the pump strainer basket. If I remove the plug and plumb the effluent tubing at the bottom of the basket where the plug was, would that provide the required pressure differential?

 

[JasonLion]

Yes, the pump drain plug will work.

Several people have hooked up their Liquidators to the drain plug. The Liquidator depends on a pressure difference to feed chlorine correctly, in much the same way that the sensors require a pressure difference to maintain a flow of water to test.

 

[woodsage]

Jason -

Thanx for the reply. I would like to understand the pressure differential. So is the idea to suck/pull water (on the suction side) from the the probe cell and then refill/supply the probe cell from the return side (influent side)?

I did plumb the effluent tubing to the drain plug of the strainer basket and I have a question: When the influent shut off valve is closed on the probe cell and the effuent shut off valve is open, should the test water in the probe cell be sucked out of the probe cell?

 

[JasonLion]

The system should be sealed, so the water should stay in when the inlet valve is closed. There isn't enough suction to create a vacuum, and nothing else can come in to replace the water, so the water stays in place.

If there is a leak somewhere, then the water might be drawn out.

 

[woodsage]

The water in the probe does stay in place when I close the inlet valve, thanx.

One other question. The default value for ORP was 650 mv and after 24 hours the FC shot up to 7,5. My target FC is 3.5 for a two person bather load, no kids, no dogs, SW Florida, screened in pool cage and no pool cover. Should I dial back the ORP target to 600 mv or less to lower the FC? Thanx, again.

 

[JasonLion]

What is your CYA level? ORP won't work right if CYA is 50 or above. When CYA is high, the ORP will be low even at high FC levels, and the unit will be constantly calling for more chlorine. Ideally you want CYA around 30 with ORP.

 

[woodsage]

I have a CYA of 140 (using a digital Palin Tester) and a ORP reading of 687 and pH of 7.7. When I use the Taylor K-2006 I have to interpolate the reading, but I'm guessing about 120...

 

[JasonLion]

ORP sensors can't distinguish between different FC levels at high CYA levels. Until you lower the CYA level below 50, the ORP controller will not work in any useful way. At high CYA levels, the ORP reading not depend on the FC level, but will rather vary with the amount of sunlight, or just at random, or always be high, or always be low, depending on various things that you don't want it depending on.

 

[learthur]

Here are some tips:

1) start by shocking your pool before going further. Maintain shock level for 48 hours.
2) consider a pH target about 0.1 lower Han what you typically use. For example I used to target 7.7 but 7.6 or even 7.5 works better for me. (insert long explanation here )
3. Get that CYA below 80. Actually fix this before you start by shocking the pool above.
4. Be prepared to see your system FC run a bit higher than usual for about 3-4 weeks.

Good luck.