Relatively New IG Pool Owner - High CYA and Condiment Algae?

[ibcj]

Hi everyone!

I've been lurking on this site for several weeks - such an awesome community. The information here is beyond invaluable!

Bought a (new to us) house last year (August 2018) and had to do very little to maintain the pool (occasional vacuum) - or so I thought. The previous owner/pool-care-guy left a bucket of 3" tabs and a float, so I bought a cheap Poolmaster test kit and just replaced the pucks as they dissolved. Occasionally added Muriatic Acid to keep pH in check and called it good. I had no issues, no algae, no problems. Well, whoops.

This season I've had my share of issues in the first couple months. Was out of town for a couple weeks and came back to a yellow/orange pool (presuming this is mustard algae), mainly starting on the shady walls. This past weekend I balanced the pH, then dumped in some liquid chlorine to start a SLAM while I waited for my K-2006 to show up. Today I measured my FC at around 10.5ppm, no CC (well, using the 0.5ppm scale at least), and a CYA of about 100 (I know this is the top end of the scale, and I just lost the dot at about 100). I didn't bother retesting the CYA as I figured anything that high (or higher) would require the same treatment course. I've been brushing daily, let the pump run for about 48h while I was adding chemicals, and today it looked like there might have been a little bit of return in a couple sections.

So it seems that the only path is to perform a drain and refill. I'm hoping to have people over next week for July 4th, so not a ton of time to get this right. I'm guessing that if I want to get a CYA down into the 30-50ppm range, and assuming I'm at 100ppm, that I need to drain 50-70% of the pool, yes? Is it safe to just close off the skimmer basket and have the pump use the main drain and exhaust the water from backwash port on the filter? Currently there is no other outlet on my janky pool equipment setup.

Looking forward to your thoughts and help. Thanks everyone!

- cj

 

[ibcj]

Also, props to whomever built the PoolMath App. I spend my life in technology, and I'm so happy to find a product (app or otherwise) that does a simple job well. I couldn't sign up for the $8/yr subscription fast enough.

Here's my results from my latest test tonight:
FC 10.5
CC 0
pH 7.8
TA 100
CH 350-360
CYA 100
TEMP 74º F(reedom units)

I was planning to bring the pH down a bit tomorrow, but thought I'd post here first before doing anything else (especially if I'm going to be draining out 2/3 of the pool).

 

[mknauss]

Welcome to the forum!
I suggest you do the dilute test for your CYA. You may have to drain a whole lot more water than you think.
100 is the limit of the CYA test, so you have to do a diluted test. Mix 50% pool water with 50% tap water. Use this mixed sample as your test water. Multiply the result by 2 for your CYA level.

I suggest you read ABC's of Pool Water Chemistry and consider reviewing the entire Pool School eBook.

 

[zea3]

Hi, welcome to TFP! Yes, you can pull from the main drain and remove water from your pool. Glad you like our poolmath app! Since you are going to start draining you don't need to do anything else to the water. You can balance it after you do your final fill on the pool.
One thing you should do is run another CYA test using a 50/50 pool water and tap water mix as your pool water sample for the test. Mix a cup of pool water with a cup of tap water then test the CYA and multiply the result by 2. This will give you a ballpark idea how much water you will need to drain.

 

[ibcj]

Marty: I have been through the ABC's and the eBook. I know everything I know from those two things! However, I didn't see anything suggesting the amount of water to drain for a given CYA reduction (but the linear math I suggested above just makes sense).

I'm not surprised you guys are suggesting the 50/50 test out of the gate. I was just trying to be cheap with the K-2006 CYA tests. I was going to order a TF kit (per recommendations here), but went with the K-2006 because I could get it in a day from Amazon Prime. Should I just order more of the CYA reagent and maintain the K-2006 for awhile, or just order the TF kit?

Will perform the 50/50 test shortly.

I am considering switching over to a SWCG. Should I just look to install one of these this weekend, and as such, drain less water to achieve the 70-80 CYA recommended for SWCG?

 

[mknauss]

The kit you have will work for the TA, CH, and pH testing for this season. You will need more FC/CC and CYA reagents. Then next spring you can get a refill for your K2006 from TFTestkits.net and you will have the right amounts of reagents for the year.

What does the water look like? If cloudy at all, you will want to follow SLAM Process prior to adding a SWCG. But otherwise, if you wish, you can drain trying to hit the 70 ppm level of CYA for a SWCG.

 

[ibcj]

The water is currently clear, Dang close to crystal clear I’d say.

 

[mknauss]

Here is clear -- TFP Clear in North Dallas - there is water in there

 

[crusemm]

Concentration initial X volume initial = concentration final X volume final. Therefore CYA init = 100 assume 20000 gal pool is final volume. Drain 50 % do initial volume is 10000 solve for final concentration (100 * 10000)/20000 = 50 ppm. If you want to drain smaller amounts do the same math substituting initial volume

 

[ibcj]

Thanks for the encouragement all. I ended up dumping the entire pool and refilled. Working on getting the balance right now, and have posted a new thread with my new numbers! You guys rock!