Can't keep FC levels up

[minsx]

I set up my new INTEX pool a few weeks ago, and tried to follow the rules for setting up seasonal/temporary pools shown in pool school.

Everything looks/works great, but I have found that my pool EATS chlorine, even with the recommended levels of CYA. For example, I can put in 11 ppm chlorine in the morning, and by the evening there is 0. Given that the 'ideal' for my pool is supposed to be between 3-7 at all times, it seems like I'd have to add small doses every 4 hours to maintain that amount properly. Am I missing something, or is this to be expected for small pools in the AZ sun? (FC consumption is somewhat slower if I leave the cover on, but that makes the pool *hotter* by the evening.)

Numbers:

FC: 0-11
pH: 7.5-7.8
TA: 180
CYA: 40

I am currently using a combination of some test strips (generally useless but they do a great job of showing if I have ZERO chlorine) and the OTO FC/pH drops.

 

[JohnN]

You say you followed the guide for seasonal pools, so I assume that means you started with dichlor, correct? How much did you add? Test strips are generally worthless, and I think CYA is one of the things they are the worst at. You would be much better off if you get a drop based kit, like the hth 6-way kit from Wal mart.

 

[Patrick_B]

The test kits we like here are the Taylor K2006 and the TF100. If you already have the pH Chlorine block, the TF 50 is a little less expensive with everything you need. Either way, you need a good kit to know what is going on in your pool.

 

[jblizzle]

I second the suggestion for the TF-50 ... that will get you all the good tests including the FAS-DPD and you will KNOW what is going on in the water.

Your loss does seem excessive. How does the water look? Could be that the CYA is lower than you think and you would benefit from adding some more.

 

[JohnN]

TF-50 is by far better than the hth kit. However, if you tell us exactly what you have added to the pool since start-up, you would be able to get by with the hth kit. Either way you need to get rid of the strips.

 

[minsx]

I did use dichlor at the start, and added enough to bring the CYA up to ~ 40 ppm, so I trusted the readings on that. I did take the water in to the pool store today and they confirmed, CYA is at 35, pH is at ~ 8.0, so those readings are pretty accurate. I'll get some solid pH down at the store today if I can to address the pH problem but it still leaves me with the FC puzzle.

If you want to know *exactly* how I set it up. . .

I put it up ~ July 2-3. I filled it with hose water (it does not have iron, etc. It's municipal AZ water). I used the pool calculator to calculate amounts for a 1200 gallon pool. I added 1/3 c. dichlor granules every evening for three evenings, and then I skipped an evening (the chlorine levels were > 10 ppm) and then I added the last 1/3 c. dichlor the next evening. (At this point I also added polyquat algaecide as a insurance at this point).

From then on out, I've been using only chlorine to keep FC levels up in the pool. I add ~ 1 cup/evening, and check it again in the morning before we swim. I may add 1/2-1 c in the mornings as well, but in the afternoon before we swim again it can read at 0 ppm chlorine.

 

[Smykowski]

Here's my guess: The CYA is on the lower range of normal, and I think the AZ sun is eating the chlorine at a faster rate than usual/anticipated. However, the wrench in the works is that you let it repeatedly get down to zero, which can allow a nascent algae bloom to start even though it's not visible. You are keeping it clear because you are diligently adding chlorine everyday, but as fast as you add it, it's used up by a combination of sunlight and "something" in the pool. It's doing the job, but just barely.
I would do an OCLT to make sure there's nothing living in the pool. If you pass, bump the CYA up to 50 and adjust your min FC accordingly. If you fail, SLAM it, then raise CYA a little. If there is a problem, the SLAM process shouldn't take very long at all.

 

[Patrick_B]

Here's my guess: The CYA is on the lower range of normal, and I think the AZ sun is eating the chlorine at a faster rate than usual/anticipated. However, the wrench in the works is that you let it repeatedly get down to zero, which can allow a nascent algae bloom to start even though it's not visible. You are keeping it clear because you are diligently adding chlorine everyday, but as fast as you add it, it's used up by a combination of sunlight and "something" in the pool. It's doing the job, but just barely.
I would do an OCLT to make sure there's nothing living in the pool. If you pass, bump the CYA up to 50 and adjust your min FC accordingly. If you fail, SLAM it, then raise CYA a little. If there is a problem, the SLAM process shouldn't take very long at all.

I like it.

I bet you are right too. With a good SLAM it will go really fast and be right as rain.