Trouble Maintaining FC Levels

[iammikeb]

Hey TFP people! I hope everyone is having a great start to summer.

We opened our pool a few weeks ago and I’ve been having a tough time maintaining FC levels this year - they are dropping so much faster. I could really use some advice. Thanks!

Here is a link to my pool: PoolMath Logs

 

[mknauss]

Low FC for very high CYA. How do you chlorinate? Can you fill out your signature?

 

[iammikeb]

I know, it’s crazy! If you look at my logs you can see I’m going through liquid chlorine / bleach (10%) pretty quickly. I’ve even resorted to throwing a couple of hard tablets in a floater to try and keep up with the loss. Given the high CYA level, I’m stumped.

 

[tim5055]

I know, it’s crazy! If you look at my logs you can see I’m going through liquid chlorine / bleach (10%) pretty quickly. I’ve even resorted to throwing a couple of hard tablets in a floater to try and keep up with the loss. Given the high CYA level, I’m stumped.

You shouldn't be stumped. You show CYA of 100, which is the max of the test so it is probably even higher. For some reason a month ago you spent $53 on dry stabilizer and you are using tabs that are almost half stabilizer.

The higher you keep the CYA, the higher you need to keep the chlorine. Even if we assume your CYA was 100 (I think it's much higher) the minimum your FC should ever be is 8 and you shlould target 11 - 13 to make sure it never goes below 8. in your testing I see that it has only been above 8 twice and never to the recommended target.

You are keeping enough chlorine in the pool to hold back a full blast of green algae, but you have stuff growing in the water consuming the chlorine.

You need to do an overnight chlorine loss test and I think it will show that you have something growing in the water.

You will need to do a partial drain and refill to get the CYA down to about 30 - 40 and then SLAM the pool

The Free Chlorine and Cyanuric Acid Relationship

Managing your cyanuric acid and Free Chlorine levels is key to stabilizing your pool. Learn how these two items affect each other.

www.troublefreepool.com

SLAM - Shock Level and Maintain

We’ve all had to deal with a green pool. Clear algae from your pool with a SLAM! Read here to use shock level and maintain to clear your pool.

www.troublefreepool.com

Perform the Overnight FC Loss Test (OCLT)

The Overnight Chlorine Loss Test tells if the SLAM is finished or if you need to start a SLAM. This article says how to do the OCLT.

www.troublefreepool.com

 

[iammikeb]

@tim5055 It sounds like I should do a partial drain (at least 25% - maybe more?) and refill before anything else. It doesn't make sense to me, to start checking for chlorine-eating living algae and slamming when my CYA is at such a high level.

I got into this mess because I was using old inaccurate test strips which were giving me extremely low CYA level readings. I bought the stabilizer and added it according to those results. Not long after I bought a TF-100 test kit and discovered I had over stabilized.

 

[Oly]

Take a look at this link to the extended CYA test, specifically item #8. CYA - Cyanuric Acid Test - Trouble Free Pool
Unless you know your actual CYA level you are guessing on how much you need to drain and refill to meet your target.

 

[DeanP66]

You need to drain at least 50%, and that's assuming that your CYA is only at 100 which it probably isnt. Anything less than that won't get you anywhere in terms of lowering the CYA to a manageable level. Like others have said, run another CYA test with diluted solution to see if it still reaches 100 or more. Don't forget to double the results.

 

[setsailsoon]

Mike,

Welcome to TFP and so sorry to hear of your problems. You are certainly not alone with this problem. We see many, many with similar problems. This is one reason we are so adamant about using a recommended test kit. Strips are worthless in most cases. I've actually done tests myself and CYA are the worst I've tested. Never got any CYA discernment over the range I looked at. Pool store reliability is only slightly better and still falls way short. Sadly, looks like you learned about this the hard way but many do.

So you need to get your CYA in shape before you can use TFP. First dilute a sample with 50% tap water and test again. Double the result and post here. Then follow the advice of experts that are already helping. You'll be in great shape in short order.

Use Pool Math app to figure out how much chemical to add based on your TF100 test results. If you have any questions about this just ask. It's the simplest way to be sure you add just the right amount of chemical.

Chris

 

[tim5055]

@tim5055 It sounds like I should do a partial drain (at least 25% - maybe more?) and refill before anything else. It doesn't make sense to me, to start checking for chlorine-eating living algae and slamming when my CYA is at such a high level.

I got into this mess because I was using old inaccurate test strips which were giving me extremely low CYA level readings. I bought the stabilizer and added it according to those results. Not long after I bought a TF-100 test kit and discovered I had over stabilized.

First, I want to say - after reading back thru my answer it may appear i was being a little hard on you. It was not meant that way.

You are not the first, nor sadly will you be the last to show up here as the victim of test strips.

As others have pointed out, a diluted test is going to gie you a better idea of how much you will need to drain and refill, but if you will be using liquid as your chlorine source in sunny AZ your final CYA goal will probably be around 50. But, before you are don you need to SLAM, and the chlorine needs for a SLAM at 50 are a lot higher than 30. But, the cost of the extra time and water to get it to 30 and then raise it back to 50 later may not be worth a little chlorine savings.

Be careful, when draining the plaster should not be left to dry out and bake in your hot sun.

While the full instructions are in the Pool School, here is the short version. Mix 50% pool water with 50% tap water. Use this mixed sample as your test water. If still at a 100 you will need to dilute more. The problem is that when doing a diluted test not only do you multiply the rage of the test you multiply the error rate of the test, so results are a ballpark - not an absolute. Here is a great chart by JamesW to explain dilution rates and what you multiply the results by to get an approximation of your CYA level.

Pool water......Tap or distilled water.........Multiply result by

....1...................1................................2
....1...................2................................3
....1...................4................................5

 

[iammikeb]

@setsailsoon Thanks for the help and support. Definitely a lesson learned the hard way. I only wish I had discovered TFP before I started all of this! Now I’m recruiting all of my pool friends and family. ?

 

[iammikeb]

Okay, better news. I did the CYA test this time with my back to the sun per Pool School instructions and my CYA is at 80. I did the test twice with two different samples to be sure. Still high, but not as bad as I initially thought.

So, we are looking at about a 40-45% drain to get my CYA around 50, correct? That math does my head in.

 

[iammikeb]

First, I want to say - after reading back thru my answer it may appear i was being a little hard on you. It was not meant that way.

It read a little grumpy and RTFM, but it’s fine. Not my first time on a forum. At the end of the day I assume you’re here to help and I’m grateful for it.

 

[tim5055]

Okay, better news. I did the CYA test this time with my back to the sun per Pool School instructions and my CYA is at 80. I did the test twice with two different samples to be sure. Still high, but not as bad as I initially thought.

So, we are looking at about a 40-45% drain to get my CYA around 50, correct? That math does my head in.

Yup, that's in the neighborhood. Draining a pool is difficult to figure exactly where XX% is anyway due to differing depths and volumes. Sometimes it's just a good guess.

So, drain/refill

OCLT

SLAM

 

[mknauss]

When you are ready to drain, let us know. You do not want your plaster exposed to the heat and sun of Phoenix. So you have a couple options we can talk through.

 

[BowserB]

Little side note. You mentioned chlorinating with bleach. That may be wrong if it is bleach with scents or additives, as many have. Also I see a lot of store brand bleach labelled "Concentrated" and the fine print says 6%--or some has no specifics of percent (so assume 6%). Find some 10% or 12.5% liquid chlorine--usually in the pool supplies section at Walmart. Where I live, a local Leslie's is still the best value at $16.99 for four gallons of 12.5%. At that price it beats Walmart's 10% chlorine after adjusting for amount of chlorine per gallon. Your location may be different.

 

[iammikeb]

@mknauss I am ready to drain. I have been reading this thread on draining. I would like to attempt to do an exchange given how much safer it is. However, there is just one part of the instructions that reads wonky to me:

Pump from the deep end or near the surface?

To determine whether you pump from the deep end of the pool or from near the surface of the pool, depends on your fill and pool water characteristic.

Adding water to the deep end while pumping from a top step or near the surface is recommended if your fill water is much colder (>20F) then the pool water.

Put the pump in the deep end and fill from the shallow end if your fill water is nearly the same temperature as the pool water, you have a saltwater pool, or have very high CH. Put the fill hose in the skimmer, if you have one, in the shallow end. If no skimmer, then use a bucket to put the water hose in and have the top of the bucket above the pool water surface. Be sure to secure the hose to the bucket.

That last line in red doesn't compute. Is it saying I should have the water hose poor first into a bucket and then spill out from the bucket into the pool rather than just throwing the water hose into the shallow end of the pool?

 

[iammikeb]

Little side note. You mentioned chlorinating with bleach. That may be wrong if it is bleach with scents or additives, as many have. Also I see a lot of store brand bleach labelled "Concentrated" and the fine print says 6%--or some has no specifics of percent (so assume 6%). Find some 10% or 12.5% liquid chlorine--usually in the pool supplies section at Walmart. Where I live, a local Leslie's is still the best value at $16.99 for four gallons of 12.5%. At that price it beats Walmart's 10% chlorine after adjusting for amount of chlorine per gallon. Your location may be different.

Thanks, @BowserB. I am confident I bought 10% bleach with no scents or additives.

 

[mknauss]

On the process, yes. If you throw the hose into the shallow end of the pool, you are not adding water at the surface. So you will disturb and mix up the stratification of the different waters. The bucket idea is just so your water will gently flow out on the surface of the pool.

With the volume you are needing to drain/refill, you might find you can rent a sump pump from Home Depot, start the drain late afternoon, it will only take a couple hours with your volume, then start filling right after. Your pool should be mostly refilled by the morning.

 

[iammikeb]

On the process, yes. If you throw the hose into the shallow end of the pool, you are not adding water at the surface. So you will disturb and mix up the stratification of the different waters. The bucket idea is just so your water gently flow out on the surface of the pool.

Okay, that makes sense.

With the volume you are needing to drain/refill, you might have find you can rent a sump pump from Home Depot, start the drain late afternoon, it will only take a couple hours with your volume, then start filling right after. Your pool should be mostly refilled by the morning.

I am open to this. However, this post scared the heck out of me in terms of draining and then filling. It's already breaking 100F here in Phoenix.

 

[mknauss]

Your pool will not pop out of the ground in Phoenix. You have no surface water table.