Testing frequency, trichlor tablets, and pale-brown deposits

[bercy]

Hi,

First off, my pool : chlorine, in-ground, sand filter, heat-pump heated, vinyl, rectangular 16x32 with 3-foot shallow end and 8-foot deep end.

I've been using Cal-Hypo and Trichlor tablets (in automatic dispenser) for many summers. I plan to start using 6% bleach. My success at keeping my water clear has been... variable over the years

I was using an OTO test kit until today, when I started using my new Taylor K-2006 kit.

Here are my readings for today:

FC: 3
CC: 0
pH: 7.7
Calcium Hardness: 200
TA: 120
CYA: 42

Water looks fine at the moment. I just added the required amount of dry acid to lower the pH to 7.5.


I have three questions.

1- My routine used to be to put 2 stabilized tablets in the chlorinator every thursday, and add a "bucket" (about 15-20 ounces) of Cal-Hypo also once a week, or more if my tests warranted it. My understanding is that the Trichlor tablets will increase CYA. At a reading of 42, should I continue using Trichlor, or just test more often and use bleach only ? Sub-question would be : does Trichlor produce FC or does it produce CC ? If it produces FC, I'm guessing that the chlorine testing frequency could be reduced by using Trichlor every week ?

2- How often should I test each component ? I understand that big rain or heat waves can be a factor, but I was thinking something like this, am I way off ? :

FC: every 2-3 days
pH: every 2-3 days
TA: every 2 weeks
Calcium hardness: every 4 weeks
CYA: every 4 weeks


3- I have deposits at the bottom of my pool. They are a pale brownish powdery substance. Any movement near the deposits will make them disappear (they are not stains). If I vacuum to waste, they will reappear within 1 day. Are those calcium deposits from the Cal-Hypo ? That's the main reason why I'm considering using bleach instead, but could it be something else ? I don't think it's sand, I think it's a much smaller grain than that, and it tends to follow whatever vinyl wrinkles I have at the bottom of my pool.

Thanks.

 

[JohnT]

Re: Testing frequency, trichlor tablets, and pale-brown depo

Welcome to TFP!

How did you come up with 42ppm for your CYA? The accuracy of that test is pretty coarse, and the markings are at 10ppm intervals. Using tabs usually drives your CYA extremely high. Mine goes up by about 7.5ppm per week.

I'd expect your deposits are dead algae that is being barely controlled.

I'd test FC with the OTO test daily until you already know what the result will be before you test. Same for pH, though you may find it doesn't take nearly as long to figure that one out.

TA and CH I almost never test for after opening the pool. They change very slowly unless you are adding things to the water that affect them. Same with CYA. If you have to add a lot of water to the pool or get a lot of rain, every 4 weeks may be appropriate, but I don't think there is really a scheduled requirement for them.

 

[bercy]

Re: Testing frequency, trichlor tablets, and pale-brown depo

How did you come up with 42ppm for your CYA? The accuracy of that test is pretty coarse, and the markings are at 10ppm intervals. Using tabs usually drives your CYA extremely high. Mine goes up by about 7.5ppm per week.

I'd expect your deposits are dead algae that is being barely controlled.

Thanks for the quick reply.

Ya, the CYA test is the black-dot test (at least with the Taylor kit), and you get to a point where you ask yourself "do I still see the dot or not". Anyway, I said 42 because it was a bit over 40.

At a CYA of 40, what should I aim for FC ? I was thinking I was fine at 3, am I wrong ?

Also, if indeed the deposits are dead algae, how do I get rid of them ? I did a complete waste-vacuum 4 days ago, followed by two days of shocking, it didn't seem to help much at all...

 

[linen]

Re: Testing frequency, trichlor tablets, and pale-brown depo

Welcome to tfp, bercy

Take a look at the link for what the dot should look like at end of cya test: http://www.taylortechnologies.com/ChemistryTopicsCM.ASP?ContentID=44 Keep in mind, the test should be done with full sun at your back and the vial held ~ waist level.

For a cya of 40 ppm 3 ppm FC is the minimum you want (per poolcalculator.com).

Also, if indeed the deposits are dead algae, how do I get rid of them ? I did a complete waste-vacuum 4 days ago, followed by two days of shocking, it didn't seem to help much at all...

The SLAM process...it is a process that you do until you pass all three criteria simultaneously: http://www.troublefreepool.com/pool-school/shocking_your_pool

 

[bercy]

Re: Testing frequency, trichlor tablets, and pale-brown depo

Take a look at the link for what the dot should look like at end of cya test: http://www.taylortechnologies.com/ChemistryTopicsCM.ASP?ContentID=44 Keep in mind, the test should be done with full sun at your back and the vial held ~ waist level.

For a cya of 40 ppm 3 ppm FC is the minimum you want (per poolcalculator.com).

Also, if indeed the deposits are dead algae, how do I get rid of them ? I did a complete waste-vacuum 4 days ago, followed by two days of shocking, it didn't seem to help much at all...

The SLAM process...it is a process that you do until you pass all three criteria simultaneously: http://www.troublefreepool.com/pool-school/shocking_your_pool

1- Seems I did the CYA test correctly, so I'll go with 40
2- I knew I'd find useful info here, had never heard of SLAMing the pool ! Great stuff.

Now, if they are algae, should I expect them to disappear once SLAM is completed, or will they stay visible and I'll need to vacuum ? And if SLAM takes more than one night, should I vacuum to waste every day ?

 

[linen]

Re: Testing frequency, trichlor tablets, and pale-brown depo

The SLAM process will eventually kill all algae (the brown stuff is likely dead algae), then it is up to the filtration system or vacuuming to remove it...but no more will show up. You can vacuum, or you might just want to try brushing first to get them up into the water and available to be filtered out.

 

[duraleigh]

Re: Testing frequency, trichlor tablets, and pale-brown depo

Now, if they are algae, should I expect them to disappear once SLAM is completed, or will they stay visible and I'll need to vacuum ? And if SLAM takes more than one night, should I vacuum to waste every day ?

Yes, they will disappear completely and not return if you SLAM correctly and then maintain adequate chlorine (3-5 ppm, but never below 3 ppm).

In my pool, I do not vacuum to waste. That algae debris will go right into your filter, be captured, and then you can clean/backwash the filter to get rid of it.

Clean/backwash your filter each time there is a 25% rise in psi on your guage.

 

[bercy]

Re: Testing frequency, trichlor tablets, and pale-brown depo

Thank you all for your input, I shall report back once SLAM is completed, maybe the post will help someone in the future.

 

[bercy]

Re: Testing frequency, trichlor tablets, and pale-brown depo

Here's my progress :

I have brushed my pool at least twice a day since I last posted.

2 days ago, after the sun had left the pool, I proceeded to raise my FC to 16 with 6% bleach. 2 hours later, I had a reading of FC:20.5, CC:0. The pool calculator suggested 5.9 x 2.85L jugs of 6% bleach, I put 6 in. Maybe my pool volume is significantly less than the 76000 litres I've calculated, or, maybe the 20.5 reading was bad, because I remember putting in 35 drops of reagent without swirling, and then needing 6 while swirling.

Yesterday morning, before sun, FC: 16.5, CC: 0.5. This time I swirled at every drop.

Last night around 9:30 pm, FC: 10, CC: 0. I wanted to raise it to 16 again, but that required 4 jugs, I had only 2 left, so I left it as-is. Anyway, this is saturday, there will be swimming, I don't want the chloring exceedingly high...

And then this morning before sun, FC: 9, CC: 0.5.

Water is sparkling.

I can't say that I've noticed a significant drop in the amount of deposits I see at the bottom.

I've taken a couple of snapshots, one in the deep end, one in the shallow end.

Deep end
Shallow end

So, as far as I'm concerned, I think I've passed the OCLT, and yet I still have deposits.

Now, water is a bit low, so I had the intention of vacuuming to waste this morning and adding new water, but maybe there's other tests you guys would want to suggest before I do that ?

Also, since I'm new to bleach, roughly how many of those 2.85 Litre jugs am I going to need every week to maintain my FC ? From the last 2 days experience it's looking like more than I was expecting ? I don't want to have to go to the store every week...

Thanks.

 

[duraleigh]

Re: Testing frequency, trichlor tablets, and pale-brown depo

Vacuum that stuff up and don't be stingy with your chlorine. It's dirt cheap in the big scheme of things.

I agree that you have passed the OCLT but I think that's dead algae on your pool floor....vacuum or brush it and get it out of your pool.

If that was my pool, I would hold SLAM value another 24 hours brushing and vacuuming any deposits on the floor.

I think you are VERY close, indeed, but I would hate to see you drop your FC prematurely. I think you have just a bit more cleanup to do

It is perfectly safe to swim anytime FC is anywhere below SLAM value so go swimming. :lol:

 

[bercy]

Re: Testing frequency, trichlor tablets, and pale-brown depo

You all seem to agree that my deposits are dead algae...

Does this mean that calcium residue from Cal-Hypo doesn't look at all like what I have (see pics from a couple of posts ago) ?

 

[duraleigh]

Re: Testing frequency, trichlor tablets, and pale-brown depo

Does this mean that calcium residue from Cal-Hypo doesn't look at all like what I have (see pics from a couple of posts ago) ?

No, it does not. If you suspect it is undissolved Cal-hypo, you should stop using it....it'll only get worse.