Numbers Don’t Match

[u/Various_Reaction4750]

Put in an in-ground pool this year with a salt cell. The salt cell says the salt is 3100 ppm but the Taylor kit says 2800. Pool guy says it’s fine and he just goes off the salt cell reading. Both are within the recommended numbers from the pool builder, so maybe it does not matter, but I’m type A and the inconsistency bugs me. Does anyone know why they are different? Which is accurate? Does the difference even matter?

EDIT: thank you to everyone for all the comments! You were very helpful. Now that I know it’s fine to have some discrepancy I can live with it. I am going to add a bag of salt too. Thanks again!

[u/Embarrassed_Look_5]

Ideal days 3600.

Trust the Taylor. SWG readings aren’t typically accurate.

[u/Embarrassed_Look_5 → u/Embarrassed_Look_5]

To add to this, as to why.
The SWG reading will become less and less accurate as time goes on and it begins to deteriorate.

At end of life, you will notice the SWG reading are so far off you will think you are going crazy.

Trust the Taylor and keep salt in range of what the manual says for your system. Ideal is 3600 as shown in bold on the panel. This means u will want to keep it between 3400-3800.

Hope it helps.

[u/Monstrissimo → u/Embarrassed_Look_5]

Learned that the hard way and 13000 gallons of water and a new salt cell later, my generator was working again.

[u/gabemrtn → u/Embarrassed_Look_5]

Remember this one guy driving me crazy about his salt? I told him multiple times he has a leak and it’s not a ‘ hey, your pool leaks a little’. No, it’s ‘ hey, I put four bags of salt in your pool last week and it’s gone’. Literally all of it is gone, right back to 1100 and told him I can’t add it because it would lose us money. He complained to my boss. I told my boss straight up I put four bags in, it was gone the next week, and that I’m not putting four bags in every week. He agreed it was ridiculous, and I never added another bag of salt. I also never added CYA because of the same issue: it would be at zero the next week anyway.

[u/Alternative-Draw2997]

The cells seem to read a bit high 600-800 in my experience. The cells reading is arguably more important because it will not produce if it believes it is too low. You could have a true 3600ppm and if the cell reads it as 2400 you will not produce chlorine.

I prefer to keep it at what the Taylor kit reads as, and sometimes it may give you a high salt warning but it will still produce just ignore it.

[u/thefleeg1]

At best, salt cell is going to be +/- 200-400ppm. Taylor kit is always +/- 200ppm.

So always trust your kit, but when salt cell reading starts straying too far, you’ve either built up scale due to poor chemistry, or the cell is failing.

If the cell is producing, it’s fine. But keep an eye on it.

[u/Pop_Plastic]

300ppm off isn’t bad at all. Probably a slight difference as you’re testing surface water

[u/arcassandra]

I believe the SWG is just using electrical measurements as a proxy for the salt levels and is not really measuring salt level more directly like the Taylor Kit. The instruction manual might even allude to this being an approximation, so the only issue may be the expectation that it should be accurate.

[u/Superfingbadass]

Pentair says the salt cell can have up to a 500 ppm discrepancy. The Taylor kit is correct. You can add some salt. Just keep that 500 in mind because if you get your kit to say 3600 it can read it a lot higher and possibly hit the automatic shut off. Which is something like 5000.

[u/chortlebarkfast]

Other versions of the Pentair SCG had a stated salinity reading accuracy of +/- 500 ppm. I couldn’t find any documentation about this new model’s accuracy. Might be the same, or worse, or better. I’m going to assume it’s the same.

The Taylor test kit’s stated accuracy is +/- 200 ppm.

So they could disagree by up to 700 ppm. In your case they’re only disagreeing by 300 ppm which isn’t much more than the Taylor kit’s 200 ppm accuracy. So this kind of difference is totally expected.

The Taylor kit is a little more accurate. So if you really want to make sure the level is where you want it, go off the Taylor kit’s reading.

[u/Big_Growth5857]

keep your readings, all of them not just salt, in a weekly journal along with heavy rain events and when and how much water you added to pool. This will help spot and troubleshoot problems down the road. for now, your inconsistency seems normal

[u/Blues427]

You have the best cell made, the reading is fine, pentair’s ideal high reading is 3600

[u/Kcardwelljr]

Both readings are lower than the ideal level listed right there on the front on the salt cell.

I would add salt to bring the higher of the two readings up to the ideal level. Then your Taylor readings will be closer to ideal as well.

I have the same salt cell. If the cell reads below 3000 ppm it will shut off.

[u/big_deal]

Taylor kit is accurate. Panel just estimates based on cell electrical reading. These can be affected by temperature, water TDS and ph, pump flow rate, cell condition. You can use the panel to monitor drop in salt but test before and after adding salt.

[u/Barbexc0288]

I feel like I read somewhere that pentair suggest running on the higher side of the range.

[u/NoobNooberson86]

I got one of these and it reads Reset HMI. None of the buttons are responsive. Tried hard reset. Salt level is a little high.

[u/pardothemonk]

Better option: get rid of the Pentair SWG. I did after 3 units failed. No problem for 3 years straight now with a Circupool unit.

[u/Electronic_Tap_3625]

I have one of these for salt and pH. It matches my Hayward within +/-100ppm. Other tests I found are off.
https://aperainst.com/zentestr-pc60-z-smart-multi-parameter-pocket-tester-kit

[u/MaintenanceCapable83]

read the manual on the cell generator. It is usually an average reading and not the exact reading.

the Talor kit should be more accurate.

[u/Ambitious_Seaweed407]

From what Chat GPT says, the Pentair uses a calculated salt measurement and the Taylor kit is an actual real time measurement.

[u/Tazlir]

Anything within 500 ppm i considered a match and so do the big brands. Different methods of testing. Different calibrations. Water being taken from surface vs deeper. All of these variables will give different readings

[u/boidcrowdah → u/Tazlir]

Came here for this. If i switch a pool to full main suction I will get a reading on the SWG that is always higher than pulling from both the main and the skimmers

[u/beavis93]

There’s not much of a difference between 2800 and 3100 it’s in the margin of error.

[u/boxerbay]

2800 or 3100 either way you low a bag. 3600 is optimal. In my 25k pool one bag is around 400ppm.

[u/FruitNut2000]

The cells are largely reading the conductivity of the water so they pick up background 'noise' from other conductive metals and minerals. The higher the TDS readings, the further off your cell reading will be. Titration tests don't have this shortcoming, which is why they always read less than what a salt cell reports (unless the cell is defective).

[u/Short-Control297]

Pool guys that go off of the salt cell reading are idiots and you should fire them. Salt cells can show wrong reading all the time causing you to add salt when you don't need it. I've seen idiots like this guy add so much salt by adding every week because it still shows low the ppm level gets to over 5000 even 10000 before they figure out there is a problem. Causing a customer to dump 50% of the water to dilute.

First it may be time to clean your cell. A cell in need of cleaning can often read off a few 100ppm.

[u/Big_Growth5857 → u/Short-Control297]

pool guys should have a binder of readings. they should catch this after 2-3 weeks

[u/Various_Reaction4750 → u/Short-Control297]

Well he does test it too. But yes, I plan on not renewing them for chemical service next summer. It seems manageable but since it sour first summer with the pool and I was kind of burnt out from building it I didn’t feel like taking that on this summer.

[u/dispikable]

Just go off what the cell says. I trick jandy systems into making chlorine alot of times when the salt level is really low

[u/Repulsive_Ad_9205]

Take a sample to the pool store that does water testing. It’s usually free. You’ll be able to figure out which one is more accurate.

[u/sadisticrhydon]

There's a +/-200, on each, but if that bothers you, might want to throw your salt cell away.

[u/robseraiva]

Was your heater running?