Low Cyanuric Acid ??

Question

When we bought our home/pool the former owner left all the chemicals and equipment including Cyanuric Acid.

Recently we ran out of it, and when I went to get more at the pool store I was told 'you don't need it, use Muriatic acid'.

My water has measured in the 'ok ' to 'ideal' level for everything else (below). I used the muriatic acid a month ago and it didn't change the cyanuric level. The muriatic acid says 'to reduce ph and total alkalinity'. If those levels are fine, why would I do that?

I'm confused as to if/why I need Cyanuric. Did I get bad info from the pool supply store?

Help would be greatly appreciated!

Here are my readings on the test strip:

Total hardness: between 250-500 ppm

Total chlorine: 3 ppm

Total Bromine: 5 ppm

Free Chlorine: between 1-3ppm

ph 7.2 ppm

Ttl. alkalinity between 80-120ppm

Cyanuric acid 0-30 ppm

Answer 1

Cyanuric acid is stabilizer. It's function is to keep chlorine from getting knocked out by the sun's UV rays. Adding muriatic acid won't do a thing for it. Muriatic is only used to effect changes in pH and TA, depending on where it's added to the pool. Shallow end in front of a return to adjust pH. Deep end away from any returns, skimmer and with main drain suction off ( if equipped), to adjust TA. It's called "slugging".

If you are using stabilized chlorine pucks, they actually contain  stabilizer in them. Not enough to dose a pool that has no stabilizer, but enough to maintain a proper level for a sand filtered pool or in the case of a cartridge filter or DE filter, eventually raise it beyond proper levels.

Your stabilizer level needs to be properly tested. That 0-30 reading is c**p and is to be expected from those test strips and not a proper titration. Too great a range of possibility here.According to that reading, you either have it or you don't. Big difference there. 0, 10, 20 or 30? You can't tell.

  If you're in a northern area, a reading of between 20-40 will be minimum to ok. Southern areas because of a heavier sun hit, require a bit more, in the 40-80 range. 100 to 130 is fine as well. Anything over 150 can be an issue, requiring a partial drain of the pool and dilute it with fresh water.  You see, you need it, but just not too much of it.

  You should be testing it's level at least twice in a season. There's no need to check cyanuric weekly. It won't creep up that fast. The beginning of the season and then mid way is just fine unless you've drained the pool at some point and need to establish the stabilizer level again or you've accidentally added stabilizer when you shouldn't have.

Stabilizer comes in a granule. Usually the bucket comes with a sock that you put the required amount of chemical in and then put that sock in the skimmer for slow dissolving of the stabilizer. It's not a chemical you will use on any regular basis. Once you've established an acceptable level, you need only test those two times during the season or if you have an issue keeping your sanitizer levels up and add if required and only after determining the cyanuric level somehow dropped below acceptable. It should never have to be a weekly thing.

The rest of those readings are ok although the pH is a little low, it's still acceptable and hopefully that calcium hardness is actually below 400 ( those test strips again!!!!!!)The only thing you need to be aware of is that you ought to be measuring either Bromine or Chlorine. Not both since you're only possibly using one or the other. Disregard what you're not using.

You also might want to ditch those test strips in favour of a proper titration test kit that does at least pH, TA and Cl/Br. They're far more accurate.

As for your pool shop giving you bad info, probably not. It's likely with all those terms being bandied about there was just a miscommunication.