Test results after partial drain refill - please advise on what to do next

[Dawngee]

Hi - new house/pool owners here…first opening and we are getting frustrated - it’s been about a month after opening the pool and still battling what we believe is mustard algae….and also high CYA levels.

Our CYA reading was 128 (Leslies) on 5/25….I also tested it when I received my TF-100 kit and got a similar result (120).

Today, we just finished a partial drain and refill process for the last several days - to try to get that level down. We have also been manually vacuuming to waste whenever seeing brown spots on the bottom of the pool. Sadly, when we got the refill up high enough to turn on the pump, the brown spots started to reappear! (They seemed a lot less when the pump wasn’t running during the refill). We hosed off the cartridge filter during the refill too.

Today’s test results (using the TF-100 kit) are:
pH 7.5
FC 4.5
CC .5
TC 5.0
CH 425
TA 110
CYA 85

Questions : I know CYA is still high but can we work with that level? I hope we don’t have to drain and refill again! What do we need to do - add liquid chlorine to raise that FC level to the CYA/FC chart level? And how much do we add?
Also I have no idea how to deal with this mustard algae issue. The pool water looks crystal clear with the exception of these brown “dirt-looking” spots that relentlessly keep appearing on the floor of the pool a day after vacuuming them out (there’s nothing on the sides).

thanks for any advice!

 

[mknauss]

A CYA level of 90 is really problematic. The SLAM level FC is 35 ppm. And maintenance levels keeps your FC above 10 ppm and that makes testing pH difficult.
You can drain an above ground pool down to half way without issue. I would suggest you do that.

 

[Dawngee]

A CYA level of 90 is really problematic. The SLAM level FC is 35 ppm. And maintenance levels keeps your FC above 10 ppm and that makes testing pH difficult.
You can drain an above ground pool down to half way without issue. I would suggest you do that.

Oh no- I was afraid you were going to tell me that. Bummer!
thank you for your response though!

 

[DeanP66]

The CYA test only goes to 100, so if the dot disappears well before 100, you know your CYA is higher, but you don't quite know by how much. In this case, you want to do a diluted CYA test with half pool water and half tap water. Mix it and then pour out half so you are back to the lower line on the bottle. Then add your CYA solution to the top line and mix and run the test like normal, but double the result at the end. This will give you a better approximation of just how much CYA you actually have.

 

[Dawngee]

The CYA test only goes to 100, so if the dot disappears well before 100, you know your CYA is higher, but you don't quite know by how much. In this case, you want to do a diluted CYA test with half pool water and half tap water. Mix it and then pour out half so you are back to the lower line on the bottle. Then add your CYA solution to the top line and mix and run the test like normal, but double the result at the end. This will give you a better approximation of just how much CYA you actually have.

Thank you. Luckily after diluting the pool I got a reading of under 100 this past time- but this is good to know.… I also bought the “standard samples” along with my test kit to make sure I’m doing the test right. CYA was a little tougher to be sure, since it seemed like the dot didn’t “disappear” (in my opinion) at the level it said (50) on the standard sample….so it scares me that I’m reading my tests “low”. Not sure.

 

[mknauss]

When you do the CYA test, try this next time.

Once you have your solution ready, back to the sun, etc. Fill the vial to a line, say 80, lower the vial to your waist level and glance for the dot, you see it, add solution to the 70 line, glance, see it, repeat until you no longer see it with a glance. Then use the CYA value one step above the line you read. So if you stopped at 50, use 60 ppm CYA.

The vial is in logarithmic scale. So it is not viable to interpolate between the lines. Just use the whole numbers, such as 50, 40, 30, ....

 

[Dawngee]

One question about draining - I have to get chlorine down to zero to drain out to wastewater sewer, but then what about my algae? Won’t it grow like crazy? The weird thing about last time is when the pump was off it didn’t seem to grow much. Hopefully that happens again? But we will be draining 1/2 the pool this time so I’m worried.

 

[Dawngee]

When you do the CYA test, try this next time.

Once you have your solution ready, back to the sun, etc. Fill the vial to a line, say 80, lower the vial to your waist level and glance for the dot, you see it, add solution to the 70 line, glance, see it, repeat until you no longer see it with a glance. Then use the CYA value one step above the line you read. So if you stopped at 50, use 60 ppm CYA.

The vial is in logarithmic scale. So it is not viable to interpolate between the lines. Just use the whole numbers, such as 50, 40, 30, ....

Got it - I will try that. Thanks for your help

 

[mknauss]

I have to get chlorine down to zero to drain out to wastewater sewer

Whom checks that?

 

[Dawngee]

Whom checks that
I just read online for Ohio that chlorine needed removed prior to draining to the sewer.

 

[Dawngee]

I just read online for Ohio that chlorine needed removed prior to draining to the sewer.