SWG and Salinity

[RafaelS]

Guys,
I have a salt water pool and wanted to find out about measuring the salinity of it. In the past couple years I just depended on the SWG (it has a control unit which displays salinity level) to show me how much salt I have. Is this a reliable source or should I perhaps buy some kind of a salinity test? The second question is regarding salinity level itself. My manual states I should keep the level between 3000-3500, the Pool School advises to keep it 300 to 400 above the recommended level, does that mean I should have about 3800-3900 salinity or is 3500 enough?

 

[bobodaclown]

You can purchase accu-check strips they tend to be ok. Your SWCG is reliable to a point. If it's happy and working I wouldn't mess with it, but as the cells wears out it will tend to get flaky and read low, you'll add salt and then next thing you know when you replace the cell your at 5000 or something along those lines.
I always like to double check. I normally test at the beginning of the season, mid way through, and in the fall. (My pool is open year round.)
Ultimately if the cell isn't happy it won't produce.
Most test swing plus/minus 400 units.

I've used these and happy with them the price is pretty good also: http://tftestkits.net/Salt-Test-Strips-Aqua-Chek-p28.html

 

[tucsontico]

I own a Taylor K-1766 salt water test kit. It is probably the best kit out there but even it is only accurate to within 200 ppm. However, it is more important what your SWG thinks the salt level is than what YOU think the salt level is.

My SWG (Pentair IC40) also displays what it believes the salinity is. My Taylor test kit results are always a bit lower than the SWG display, e.g., today's test =3300 vs 3400 SWG reading. I consider that well within the tolerances of Pool School recommendations.

 

[svenpup]

There are drop style test kits (e.g. Taylor K-1766) and also the AquaChek Salt Test Strips are considered acceptable.

It is a good idea to use these periodically to compare to the SWG reading. Low SWG reading can indicate scaling on the cell, or (later) imminent cell failure.

If you target 3500 (high end of recommended) that will be fine.

 

[JasonLion]

I own a Taylor K-1766 salt water test kit. It is probably the best kit out there but even it is only accurate to within 200 ppm.

The K-1766 is +-400 when measuring levels around 3000-3500. It is only +-200 below 2000.

 

[YippeeSkippy]

I test with the K-1766 kit. This year my salt level is low at 2900, yet my Compu-pool SWG thinks its close to 4500. Since I run it on a fairly low output setting (20% @ 8 hours currently) and its working very well..... well... who am I to complain? LOL. I've got salt to add when the unit gives me any hint of needing it. But it seems kinda happy now so.. <shrug>

 

[RafaelS]

So I got my salt test kit as you guys suggested K-1766 and just read 4200 as my salt level. My SWG was showing 3300 when I looked this morning but 3600 yesterday, maybe still mixing up salt from when I added it earlier this week? Am I adding the drops until the color turns salmon red all the way ? or is it enough when the color just changes slightly and goes back to yellow. If my level truly is 4200 am I in trouble ? I really have no way to refill my water as I have a well and using the hose drains my system terribly. In addition I just had a new well pump put in and its still clearing out he chemicals, town still has to come approve the water for usage.

 

[JasonLion]

Unless your SWG has shutdown because of a high salt reading, you are fine.

Both the SWG and the test are +-400, so those readings are very nearly the same as each other within the precision of the tests.

 

[SunnyOptimism]

Thanks for this thread!! I will go and get a Taylor test kit. I have the AquaCheck test strips but I much prefer titration/colorimetry.

Also, with regard to everyone that has commented on their salt cells reading the salt level, I believe all cells are inherently inaccurate (read high) because the feedback is simply based on the conductivity of the water in the cell (V = I x R) which is proportional the Total Dissolved Solids (R ~ [TDS] where [TDS] = [Na+] + [Ca++] + ....) and not specifically sodium chloride. TDS is the combination of all conductive ion species in the water of which sodium chloride will be the major component in an SWG pool. My guess is that if you rely solely on the output of the salt cell to tell you the ppm levels, you'll always end up in a salt-starvation mode towards the end.

Just my two cents....

 

[RafaelS]

Thanks Jason