Very Interesting Problem

[CarlD]

1 gal of 12.5% chlorine will raise 1000 gal 10 ppm so these pools are needing LARGE amounts of chlorine to reach breakpoint (12 ppm and up)!

WHOOPS!!!! This math is all wrong! 1 gallon of 12.5% chlorine will raise 1,000 gallons of water to 125ppm! 'Way, WAY too high. Lost a zero somewhere. It will raise 10,000 gallons to 12.5ppm, rather than 10ppm, assuming, of course, that the 12.5% didn't break down to 10% (which is likely). If it has broken down to 10%, then, of course, it will only add 10ppm, not 12.5

Test strips, although they do give accurate results, do NOT have the precision (resoluton) to base water chemisty adjustments on! For example, how can you ajust pH when all you know is that the pH is somehwere between 7.2 and 7.8 which is what the majority of strips will tell you?

Waterbear is using his language very, very precisely ( ) here. It is extremely easy to get spurious results with most test strips. If you run the test even slightly wrong, or there's the tiniest contamination on the strip, you'll get bad readings.

Pools with very high TDS from old water that have been using stabilized chlorine will also have very high CYA levels. The problem is NOT from the high TDS but from the high CYA. Both readings go up when the water is old. If high TDS had an effect then every pool on a SWG would be in trouble since their TDS is going to be higher than their salt reading and well above what is considered to be too high (even in new pools), which is a part of the measured TDS! Obviously, this is not the case.

The accepted cure for high TDS is to drain and refill, exactly the same as for too high a CYA reading! Which is the culprit, TDS or CYA? I put my money on CYA every time!

IF you want to make your customers happy invest in one of the water labs available to the industry from companies like Tayor or LaMotte and stop using the strips so you can accurately diagnose what is going on in their pools!

Other than that, I sure appreciate Waterbear doing my job so I don't have to!

[waterbear]

WHOOPS!!!! This math is all wrong! 1 gallon of 12.5% chlorine will raise 1,000 gallons of water to 125ppm! 'Way, WAY too high. Lost a zero somewhere. It will raise 10,000 gallons to 12.5ppm, rather than 10ppm, assuming, of course, that the 12.5% didn't break down to 10% (which is likely). If it has broken down to 10%, then, of course, it will only add 10ppm, not 12.5

Math neve was my strong piont. Niether is typoing I dropped a 0! (and I treat 12.5% chlorine as 10% because it probably is by the time it goes in the pool! I was rounding off for simplicity. 100 oz is closer to 3 1/4 qts. (10 oz of 10% will raise 1000 gal 10 ppm) Thanks for catching that, Carl!

My point still holds. These pools are needing HUGH amounts of chlorine to reach breakpoint. 12 to 16 gallons in a 10000 gal pool means 120 or higher ppm chlorine!

[CarlD]

Math neve was my strong piont. Niether is typoing I dropped a 0! (and I treat 12.5% chlorine as 10% because it probably is by the time it goes in the pool! I was rounding off for simplicity. 100 oz is closer to 3 1/4 qts. (10 oz of 10% will raise 1000 gal 10 ppm) Thanks for catching that, Carl!

My point still holds. These pools are needing HUGH amounts of chlorine to reach breakpoint. 12 to 16 gallons in a 10000 gal pool means 120 or higher ppm chlorine!

LOL!

Remember my rule of thumb: 1 gallon will add EXACTLY it's concentration to 10,000 gallons. So 1 gal of 5.25% adds 5.25ppm FC, 1 gal of 12.5% adds-----10ppm! (when it should add 12.5ppm--and will if it's new and properly stored).

Yes, your point still holds. But a ppm of 120 is bad, real bad...I sure hope it isn't a vinyl pool. If CYA is that high, then water replacement is the best option.

[waterbear]

LOL!

Yes, your point still holds. But a ppm of 120 is bad, real bad...I sure hope it isn't a vinyl pool. If CYA is that high, then water replacement is the best option.

Said that! (at least implied that on my rant about TDS!)

[F3AFlyer7]

Hmm...


See I originally thought it was the CYA also. However, these are all happening on pools that are being opened for the first time this season. We check their stabilizer every year because we drain our pools half in the winter. They all have very low stabilizer from the loss of water. So that means the too high CYA level is not the problem. As for our strips, the FC and the TC are the levels we are looking at for this problem. When this problem occurrs, its never on the slightest of hugh difference. Its always a major difference and definitely noticable every time. Large amount of TC, and no FC, any more chlorine added doesnt show up until a break point shock.

[waterbear]

Hmm...


See I originally thought it was the CYA also. However, these are all happening on pools that are being opened for the first time this season. We check their stabilizer every year because we drain our pools half in the winter. They all have very low stabilizer from the loss of water.

BINGO! Closed pools can lose CYA by biodegrationl. The lowered levels are not completely from the loss of water. A 50% drain will only remove 50% of the CYA. I will bet money that your levels are lower than that after refilling! Anerobic bacteria will eat the CYA and excrete large amounts of ammonia and urea. Symptoms are high TC and FC not holding until the ammonia compounds are burnt off. Not a recognized phenomenom but one that has had much discussion in this forum and there is research that backs it up. Don't have time to find some of the other threads on this right, have to get to work very soon, but there are several with links to some of the science behind it. You need to compare the CYA level on closing with the level on opening BEFORE you refill. If the CYA has dropped that is the problem.

[CarlD]

Hmm...


See I originally thought it was the CYA also. However, these are all happening on pools that are being opened for the first time this season. We check their stabilizer every year because we drain our pools half in the winter. They all have very low stabilizer from the loss of water. So that means the too high CYA level is not the problem. As for our strips, the FC and the TC are the levels we are looking at for this problem. When this problem occurrs, its never on the slightest of hugh difference. Its always a major difference and definitely noticable every time. Large amount of TC, and no FC, any more chlorine added doesnt show up until a break point shock.

I suggest you stop using strips and go to drop testing kits, and get one with FAS-DPD powder testing of chlorine. You will get more precise and reliable results. TC and FC tabs on strips rarely match up correctly. Since TC = FC + CC, you will be better off getting a direct CC reading from FAS-DPD.

The tabs for CYA, CH, and pH are nearly unreadable on strips--so much so I consider them nearly worthless. But drop testing, again, will give a much better read.

CYA should not drop so much unless the water has lots of contaminants that metabolized it. Draining is simple: Drain half your water and refill and CYA will be cut in half. If it was high, like 100ppm, then replacing half the water takes it to 50--a high but reasonable figure.

[gonefishin]

Hmm...


See I originally thought it was the CYA also. However, these are all happening on pools that are being opened for the first time this season. We check their stabilizer every year because we drain our pools half in the winter. They all have very low stabilizer from the loss of water. So that means the too high CYA level is not the problem. As for our strips, the FC and the TC are the levels we are looking at for this problem. When this problem occurrs, its never on the slightest of hugh difference. Its always a major difference and definitely noticable every time. Large amount of TC, and no FC, any more chlorine added doesnt show up until a break point shock.

Hi F3AFlyer7,

I know that you posted earlier that you primarily use test strips. But do you also have a drop kit? If you had a complete (or at least more complete) set of numbers from a customer or two (both end of last season and this season) it seems that some of the other members here may be able to help you better. They've really only got a description of the signs and symptoms of what has happened and is happening. It would also be useful to see what some drop tests say along side these signs and symptoms.

First off...let me say that I am a complete pool newbie! Let me second say...I love Ben's kit. It has not only been an instrument in getting me off to a good start with my pool water...but it's also contributed to my understanding of why I needed to stabilize my water and what changes took place to implement those changes. I'm learning...slowly but surely

take care,
dan