CYA issue

[zed88]

Hi everyone,
I'm running into the same issue I had last year and I figured its time to ask here

My cya appears to be out of control, and I have mustard algae that continues to grow and I fear thats thats the issue. Here are my current levels:
FC 11.5
TC 13
Alkalinity 120
CYA is 100+
CH 300

As far as I can tell everything is ok except the cya, which I believe is stopping the cholorine from working properly and allowing stuff to grow. I've cleaned up all my plumbing and it as no leaks and appears to be filtering very well. Water clarity is ok but hazy and with obvious growth at the bottom (less than 12-15 hours after vacumning). I'm also in an agrument with a family member who helps me on this and is not into chemistry but is positive its not the cya levels.

I've also attached pictures of the chlorine tabs and shock packets we are using.

A direction to head in would be appreciated (even if I have to dilute the water, and a plan to keep cya from rising again).
Thanks!
Eric

 

[Mr Bruce]

It's like asking "I've been dumping rocks in my pool, is that why my pool is full of rocks?!"

Yes, the "shock" is just adding to the CYA, it's likely at over 100, you will need to replace water. Pool School - Chlorine / CYA Chart

"The plan" should be to use bleach to chlorinate moving forward. It might be a good time for a refresher Pool School - ABCs of Pool Water Chemistry

 

[pooldv]

Chlorine level is set based on CYA level and the [FC/CYA][/FC/CYA]

 

[zea3]

You are correct. Your CYA is way too high, even by pool store standards (they say 30-100ppm, we say 30-50ppm). You can run the CYA test again using 1 part tap water mixed with 1 part pool water as your test sample. Read the result and double it for an estimated CYA level. This will help you determine how much of the pool you need to drain.

You don't say if this is an above ground or inground pool, and if it is inground is it plaster, vinyl liner, or fiberglass? The type of pool will determine the safest way to drain and refill.

Your signature shows high iron in your well water, so you will need to make sure you use sequestrant on a regular basis to keep the iron in solution.

 

[zed88]

Finally made some good progress the least 2 days. CYA was around 180-200 as far as I could tell. We had been using the above shock and tablets for 2.5 years and I think it just kept adding up. We always keep it covered to we rarely have to add more than a inch of water, and don't ever lose water. Its a 18 foot above ground vinyl, and I would let it drain about 40% and then fill it back up. CYA is now down to around 70 or so which I am ok with for now. Next year I may do another drain/refill but right now my water bill will already be another $100 higher for the 5000 gallons or so just used.

I also ran out and purchased a bunch of the correct bleach, ash, and muratic acid, and some measuring containers. I'm going to hold off until everything is perfect to work on the borates. I also already had a TF100 test kit with extra's and a speed stirrer.

After letting it circulate for a few hours I have begun attacking my TA (its actually city water with high iron, and I had to do this when we filled the pool a few years ago. Gives it a very green tinge that goes away after 48 hours of filtering).

PH 7.0 (keeping a close eye on it and using acid to keep droppign it back to 7.0)
FC 8
TA 200-220 (do you stop at "red" or "pink"
CYA 70
CH300

I will keep everyone appraised of the progress and show some pictures later.

 

[zed88]

Its starting to clear up as I remove the iron from the water (green haze going away). Also dropped the cya further and should be good from here out. Here is where we currently sit:

PH 7.4
FC 6
TA 200
CYA 35
CH 400

I expect a sparkling pool in another day or so (although we have a huge storm system rolling in today).

 

[zed88]

Starting to look like true trouble free pool. Slamming right now to get rid of the algae that was starting to grow on the bottom (weird to watch it grow over the course of the morning). Vacuumed and brushed it all off after raising the FC level. Now checking it every hour or two to keep that up.