Started SLAM without knowing CYA level...

[binyamingavriel]

So I had someone open my pool, primarily because it's hard to find the time when you work 2-3 24 hr shifts a week plus. I would like to try and stick with the TFP method and use liquid bleach. Unfortunately, he used powder shock to get me started. Either way, I neglected the pool for a week or so when heavy rains and very high pollen conspired against me and returned me to swampy conditions.
I found some 10% chlorine at Home Depot and started adding a fair amount, but while waiting for more CYA reagent I only had the other numbers to go on. During this time my FC was hovering around 6-8. At the same time I couldn't vacuum very efficiently, as my skimmer plate had broken and wouldn't maintain a good seal. I replaced that with a Vac Mate, which seems to be (finally) working properly (although it will likely be the topic of a new thread). Bottom of pool is much cleaner now, and CYA reagent arrived today. I've always estimated my pool volume at 30K (based on rough estimate of 20x40 ft.) , but perhaps it should be closer to 36K or even 39K gallons.
Current results:

• FC = 6.0
• CC = 0
• pH = 7.8
• TA = 90
• CH = 350
• CYA = <10

So where should I go from here? I figure I need to add some CYA (to what level?) and also figure the best way to maintain adequate FC level (what's the best way to do this when using LC? Frequency of testing?)
Thanks in advance

 

[mknauss]

What is the location of this pool? Can you add your city/State/Country in your Profile?

Also add a signature - see Pool School - Read This BEFORE You Post. Be sure to add what test kit you are using.

Your CYA is very low. It should be at least 30 ppm for a SLAM Process. You should lower your pH to 7.2 and then follow the SLAM process. Use [FC/CYA][/FC/CYA] for the appropriate FC. Test your FC and dose with LC every couple hours to start.

 

[Mendy48]

Swampy Condition huh? Time to SLAM!!
Do you have your own test kit. If so, which one?
Are these your own test results? If so, you need to SLAM your pool.

First, you'll need to bring your pH down to a 7.2 by using muriatic acid to lower the level of your pH. You want to add the muriatic acid at the return into the pool with the pump running. You should pour it in a pencil size stream. Some people like to use measuring devices, so if you want to use a measuring device, transfer the acid to the measuring device as close to the surface of the pool water as possible. Please DO NOT pre-mix the acid with water in a bucket. After adding, mix with a brush. Note: Make sure to use PoolMath to get an accurate measurement of how much you need.

Next, you'll need to bring your CYA up to a 30. Use PoolMath to determine how much stabilizer you will need to add. To add a stabilizer, I recommend you add the granular in a sock and hang it close to your return jet. You can gently massage the sock to dissolve the granular once you have it hanging in your pool (at least that’s what I do). It speeds up the process a bit. Wait 24-48 hours before you retest again your CYA. Nevertheless,you can go ahead and start the SLAM. You don't want to delay that waiting for the CYA to dissolve entirely.

As your CYA is dissolving, you can bring your FC to shock level for a CYA of 30 (and that would be 12)- FC/CYA - Maintain your FC at a 12 by adding bleach (the plain stuff..no additive) or by adding liquid chlorine (Sold at Walmart or Home Depot at 10%) when necessary. Use PoolMath to determine how much chlorine you'll need to reach shock level. Make sure you leave you pump running 24/7 while SLAMing your pool (proper circulation/filtration of the pool water is recommended).

Brush Brush Brush your walls and ladder area while in SLAM mode. Once pool is clear, its time to perform the following. Here’s the link: Overnight FC Loss Test (OCLT)

 

[binyamingavriel]

What is the location of this pool? Can you add your city/State/Country in your Profile?

Also add a signature - see Pool School - Read This BEFORE You Post. Be sure to add what test kit you are using.

Updated

You should lower your pH to 7.2 and then follow the SLAM process.

It may be a couple of days until I can get hold of the acid. Can I or should I add the CYA in the meantime? Also, just realized that I don't have enough CYA. If I can add it now, is it better to wait for full amount or can I do it stepwise (half now and half in a couple of days)?

 

[mknauss]

Add the CYA. No harm in that. It will lower your pH a bit.

Thanks for the update. Helps us understand the climate you are dealing with.

 

[binyamingavriel]

I think I overshot the CYA a bit. I tested today and it looks to be around 50. The water level has gone down a bit from evaporation, so I refilled and I'm going this brings it down a bit, although I figure it will be a very modest reduction. Anyway, looking forward to OCLT. If I'm not at shock level, but above recommended FC level, can I still do it? Perhaps I'm wrong, but I assume once you reach the shock level you then let it drift down to the recommended level.

 

[mknauss]

SLAM with a CYA of 50. Evaporation does not reduce CYA. It stays in the water, like salt and calcium.

Maintain the FC at SLAM for a day and then run OCLT tomorrow night.

 

[binyamingavriel]

I know evaporation wouldn't lower CYA, but I meant that replacing the evaporated water with fresh water would.

 

[mknauss]

I doubt the volume of water you are adding due to evaporation is more than 5% of the pool volume, so not significant.

 

[binyamingavriel]

On a related note, is there a need for further CYA testing this season, or can I assume minimal change if I only use LC?

 

[mknauss]

You should test your CYA monthly when your pool is open. It does degrade some and you will lose some due to backwashing your filter.

 

[binyamingavriel]

Out of curiosity, is there a calculation as to how much gets lost due to degradation and backwashing?
And thanks for your help and patience. Progress is definitely being made!

 

[mknauss]

For degradation - it varies. Most in your climate do not see much, maybe 3-5 ppm per month. I see much more here in the SW desert in the summer. Backwashing depends on how much water volume you replace each time you do that procedure.

 

[binyamingavriel]

Hopefully starting OCLT tonight. Should I keep the pump running overnight for it?
EDIT: Also, must I wait for sunset or is it enough that the sun has dipped below my roof line and the pool is now in shadow?

 

[binyamingavriel]

I blew it! Ran out of reagent mid morning test! That'll teach me to use 25mL samples! New batch won't arrive until Thursday. Can I just test at that level then or should I bring it back up to shock first?