pool test results

[momof4]

Hi there,

I have a 31000 gallon salt-water (zodiac swg) in-ground pool, vinyl liner. This is our first season and we are just learning all the ins and outs of pool chemistry. My latest readings (from the pool store) are:

t.d.s. - 1000
stabilizer - 40
mineral - 3620
total chlorine - 5
free chlorine - 5
ph 7.5
t.a. - 150
adj. t.a. - 135
c.h. - 185
algae - none
clarity - clear


the pool looks good - my concern is that the chlorine value is at 5 -- I've read conflicting things about the recommended level, but I think it should be lower than this. Is it safe for kids to swim at this level? I know that with the salt-water pool, chlorine is still the sanitizer, but I thought the levels were kept quite low (like closer to 1). We did have to do a "super shock" last week in an attempt to deal with phosphate levels of 500 ppb. Phosphates seem to be ranging from 200-500 ppb...not sure why - neighbour fertilizing? scale inhibitor? leaves in the pool? Are phosphates alone, aside from the algae concern, an issue for swimming safety? At what level should they be dealt with? If I leave the cover off for awhile, will the chlorine burn off? Should the swg be turned off to bring chlorine levels down?

Also, is the walmart test kit good enough for the occasional comparison with the pool company readings (we get free water testing there) and to just keep an eye on ph/free chlorine levels?

Also pool company recommends bi-weekly addition of 300 ml of scale inhibitor (bioguard) - is this really necessary? Hate to add chemicals that aren't really needed. They also recommend once a month lite shock + mineral renewal addition...is this a good idea?

Final question - what's the difference between adding lite shock and hitting the superchlorination button on the swg?

Thanks for any help...this site is a great resource!

 

[reebok]

this site is a great resource and you'll find lots of good information in pool-school/
one of the things you will find is that your fc level depends on your CYA level (your store calls it stabilizer). you don't have enough CYA/stabilizer for an SWG, but yeah it's fine to swim in. you should add some CYA to get up around 60-80ppm.
I also recommend not getting your water tested at the pool store and getting your own test kit. pool stores are notoriously wrong. there is more on test kits in pool school.
also, phosphates are irrelevant in a properly sanitized pool. there is one member here who has I think it was 3,000ppb phosphates. most people don't even have it checked.

pool-school/chlorine_cya_chart_shock - chlorine/CYA chart. you fall under SWG (though you don't have enough CYA to even make the chart)
pool-school/water_balance_saltwater_generator - good tips on water balance for SWG's
pool-school/pool_water_chemistry good overall water chemistry information including about phosphates

 

[JasonLion]

With CYA at 40, an FC level of 5 is perfectly normal. The normal range with a SWG with CYA at 40 is between 2 and 7. You don't need to keep FC up that high, so you can go ahead and turn down the percentage on the SWG a little. Then the FC level will fall on it's own. You will probably need to test the FC level and continue adjusting the percentage on the SWG a couple of times before you get it to the perfect level.

Phosphates are not a problem at all. Pool stores like to use phosphates as a scare tactic to try and get people to buy expensive chemicals they don't need. My phosphate level is over 4,000 and I haven't had any problems at all.

With a SWG, you really should raise your CYA/stabilizer level to between 70 and 80.

The super chlorinate button on the SWG is not very useful. When shocking you want the FC level to come up very quickly. But a SWG is designed to release chlorine very slowly and steadily, so it isn't very good to use the SWG to try and shock.

Shocking regularly is not required. You only need to shock when you are having problems.

Your "mineral" level is fine, you probably don't need to add any more this season. "mineral" is just a fancy name for salt. You can probably get a suitable kind of salt for way less than what the pool store is selling it to you for.

It is unlikely that you need the scale inhibitor. It is mostly there to prevent metal stains, but if you don't have any metals in the water, you won't get any metal stains even without that product. On the other hand, if you do have metal in the water you need it. I would stop using it and see if anything happens. At the first sign of staining, and some scale inhibitor. If no stains develop then you can stop using it.

 

[frustratedpoolmom]

Great advice so far, I'll just add the Wal-mart kit is not enough for your pool, the two test kits we recommend are the TF-100 and the Taylor K-2006.

This article compares them, IMHO the TF100 is the better deal of the two.

 

[momof4]

Thanks so much for the advice - very helpful. Is the TF100 test kit available in Canada?

 

[frustratedpoolmom]

No. Your best source for the K-2006 is Apollo Pools.
http://piscines-apollo.com/english_taylor.htm

 

[dmanb2b]

unfortunately not but the taylor k2006 is...from apollo pools....toward the bottom of the page...the price seems just a little high, but hopefully someone from CA can confirm here

http://piscines-apollo.com/english_taylor.htm

edit: Sorry FPM beat me to the punch..at least I know I sent you to the right site

 

[momof4]

Now I'm really confused. I took a sample in this morning to the pool company - ph 7.5, fc - 3, total c - 3, stabilizer - 40, t.a. - 160, ch 155 and they said I had perfect water balance (brought the sample in within an hour of taking it from the pool)

then, just to compare - I bought a 4 way hth kit at Walmart - the strips (hard to read in the sun, by the way) say somewhere between 3 and 5 for free cl, the ph was somewhere between 7.8 and 8.4 level, ta didn't really match anything, but was closer to the 180-240 end of the scale and cya was 30-50. How can ph be that different? Which test do I go by? Should kids swim if ph is really that high?

I'm trying to get a Taylor kit - hard to come across in Canada for a reasonable price - may have to go over to the states (we're near the border) to pick one up. In the meantime...what do I do?

 

[MikeInTN]

In the meantime, get the HTH 6 way kit from Walmart. It should be more accurate than the strips. The strips are notoriously wrong, which is why they're referred to as "guess" strips here.

 

[momof4]

our Walmart didn't stock the 6 way kit...I guess I'll just trust the pool company results for now until I can get a better kit...sigh!