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Thread: Salt concentration sensor accuracy

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    Salt concentration sensor accuracy

    I've got an Aquapure 1400. Love the thing. This summer, salt sensor in the system measured between 4.1 & 4.2 all summer. I did not add any salt and figured salt level would decrease to normal soon enough, but it never did. Then we got a sudden cold snap here in AZ and salt concentration (as measured by the Aquapure sensor) suddenly dropped almost overnight to 2.3. I used a salt strip to measure level, and it said it was way high, but not sure I can trust those results either. Any chance the Aquapure sensor's accuracy is affected by air/water temp?
    16,000 gal in-ground Pebble-tec pool / Pebble-sheen spa. Jandy AquaPure 1400 SW Cl gen (SWG) system. In-floor cleaning system w/ Hayward EcoStar 2.0 HP VSP pump. Hayward 31" sand filter. 900 sq ft Heliocol solar panels (on roof) w/ separate 1 HP Pentair WhisperFlow single speed pump. Water feature with separate Hayward 0.85 HP VSP pump.

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    Re: Salt concentration sensor accuracy

    The salt sensor on a SWCG actually measure electrical conductivity of the water. The higher the salt, the more conductive. They are calibrated at the factory to measure a certain range of conductivity when the salt level is in the "good" range.
    Conductivity is affected by temperature of the water. Once the water temp starts to drop below 70 degrees or so, the conductivity drops off sharply. Therefore, you have a lower salt reading in the winter. When the water temp is cold, the strips will be more accurate as compared to the meter on your SWCG.
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: Salt concentration sensor accuracy

    Got it. Thanks for the quick reply. Still a little weird that the salt level would stay so high all summer without adding any salt. I would think that with evaporation and rain (not that we get much rain here), the salt level would drop, but it never moved below 4.1 all summer. It was really hot here, so maybe the higher air/water temp in the summer was causing slightly higher readings then.
    16,000 gal in-ground Pebble-tec pool / Pebble-sheen spa. Jandy AquaPure 1400 SW Cl gen (SWG) system. In-floor cleaning system w/ Hayward EcoStar 2.0 HP VSP pump. Hayward 31" sand filter. 900 sq ft Heliocol solar panels (on roof) w/ separate 1 HP Pentair WhisperFlow single speed pump. Water feature with separate Hayward 0.85 HP VSP pump.

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    Re: Salt concentration sensor accuracy

    Rain will dilute the salt, sure. How much depends on the amount of rain. However, evaporation will not cause a change in the total amount of salt. The salt stays in the water, it doesnt go anywhere when water evaporates. If anything, the salt concentration will actually increase a bit when water evaporates.
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: Salt concentration sensor accuracy

    Makes sense. It was a VERY dry summer here. Thanks again.
    16,000 gal in-ground Pebble-tec pool / Pebble-sheen spa. Jandy AquaPure 1400 SW Cl gen (SWG) system. In-floor cleaning system w/ Hayward EcoStar 2.0 HP VSP pump. Hayward 31" sand filter. 900 sq ft Heliocol solar panels (on roof) w/ separate 1 HP Pentair WhisperFlow single speed pump. Water feature with separate Hayward 0.85 HP VSP pump.

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    mas985's Avatar
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    Re: Salt concentration sensor accuracy

    Most SWGs built these days compensate the salt readout for water temperature. Mine stays within a 100 ppm or so over 45 degrees to 100 degrees of water temperature. I would be very surprised if the Jandy didn't do the same but you might want to check with them just to make sure.

    If it does compensate for water temp, then there might be another issue.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Salt concentration sensor accuracy

    I'm not sure thats across the board. I didnt know Aqualogic did that though. I know Pentair doesnt. Anything below 70 it starts to drop off a bit. Below 65 and its not accurate at all.
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: Salt concentration sensor accuracy

    Hillyjd

    Scale can build up on the sensor and cause inaccurate readings.
    You can clean the contacts with the green household scrub pad/sponge.
    Should take less than 10 minutes.

    If you are unsure how to access the sensor, here is a link to the owners manual.
    Instructions begin on page 30.
    http://www.jandy-downloads.com/pdfs/AquaPure_Manual.pdf

    Check the flow/temp/salinity sensor connections and the wiring to the sensor.
    poolschoolgrad

    20x40 free-form IG vinyl, 1hp Hayward superpump, Hayward pro grid DE filter, Raypak heatpump, Goldline Aquarite SWCG, Polaris 280 with booster, and tested using a Taylor K2006.

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    Re: Salt concentration sensor accuracy

    Hillyjd,

    What's your water temperature?
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: Salt concentration sensor accuracy

    Water temp about 49F - SWCG control box shows "LO" which I think means water is too cold to worry about generating chlorine. Funny thing is, chlorine level has been REALY high the past few weeks. Literally off the chart. I had the SWCG set at 10%, but can't seem to get the chlorine within limits. Not sure the two issues are related; just strange.
    16,000 gal in-ground Pebble-tec pool / Pebble-sheen spa. Jandy AquaPure 1400 SW Cl gen (SWG) system. In-floor cleaning system w/ Hayward EcoStar 2.0 HP VSP pump. Hayward 31" sand filter. 900 sq ft Heliocol solar panels (on roof) w/ separate 1 HP Pentair WhisperFlow single speed pump. Water feature with separate Hayward 0.85 HP VSP pump.

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    mas985's Avatar
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    Re: Salt concentration sensor accuracy

    Quote Originally Posted by bk406
    I'm not sure thats across the board. I didnt know Aqualogic did that though. I know Pentair doesnt. Anything below 70 it starts to drop off a bit. Below 65 and its not accurate at all.
    That is surprising since temperature correction for salt readout is a fairly easy thing to do if the cell has a temperature sensor. Obviously, if the cell doesn't have a temperature sensor, then it couldn't do any correction.

    The Aquapure 1400 does have temp sensor so I would assume that they would take advantage of that and display a calibrated salt level. The Intellichlor also has a temperature sensor so assuming it is installed, I would expect some level of temperature compensation for the salt read out but they may have decided not to do that for some reason. But I am curious as to how much error do you see at the various temperatures? It could be that they just don't do a very good correction.

    Without any correction and zero error at 80 degrees, I would expect the readout error to be about -350 ppm at 70 deg, -680 ppm at 60 deg and -1000 ppm at 50 deg.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Salt concentration sensor accuracy

    Mark


    Your calculations are pretty spot on for temp and salt reading drop off. Even though there is a temp sensor, they won't correct. They're not set up that way. At 49 degrees, that swg won't read accurate at all. The reason the FC is high is that at those water temps chlorine use is very low.
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: Salt concentration sensor accuracy

    Thanks for all the info. VERY informative. Being an engineer by trade, you'd think I could figure this out on my own. I guess I can worry less about the salt concentration at the moment and focus on my next disaster - got so cold here last night that the pressure regulator for my autofill system burst. Luckily there's a shut off valve so I don't have to turn all the house water off. It's always something.
    16,000 gal in-ground Pebble-tec pool / Pebble-sheen spa. Jandy AquaPure 1400 SW Cl gen (SWG) system. In-floor cleaning system w/ Hayward EcoStar 2.0 HP VSP pump. Hayward 31" sand filter. 900 sq ft Heliocol solar panels (on roof) w/ separate 1 HP Pentair WhisperFlow single speed pump. Water feature with separate Hayward 0.85 HP VSP pump.

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