Chlorine Demand Test = 83 lbs!

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jjoshua

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May 23, 2009
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My 15,000 gallon plaster pool is having a chlorine demand problem. The local bioguard dealer ran a chlorine demand test and came back with 83lbs of their burnout extreme which is cal-hypo 47%.

I'm not going to use the bioguard product because it is too expensive and cal-hypo is going to raise the hardness through the roof.

What can I do to fix this problem?
 
Post a complete set of testing results.

You will need a good testkit to get these results, but for starters you could post what the pool store gave you.

Then chlorine, liquid bleach will provide all the chlorine that you need without the use of cal-hypo.

dave
 
There is a bucket test you can do to figure the chlorine demand. 1/8th of a teaspoon of 6% bleach in 1 gallon of water is around 10 ppm FC. (If you use more water it's probably easier to measure the bleach; e.g. 4 gal water and 1/2 tsp bleach.) Add bleach, stir, let it sit a few minutes, then test. Repeat until you hold 10ppm. Now you know how many ppm of bleach to add to the pool, before it will hold at 10.
--paulr
 
Typically, we do not use chlorine demand on the forum.

Your Pool Store should not be using it, either. 83 lbs of Cal Hypo in your pool is so over the top as to approach absurdity.

Anyway, thanks for the test results. Tell us how your water looks and how long it has looked like that?
Well get your pool clear......stay away from that pool store
 
jjoshua said:
TC = 4
FC = .2
PH = 6.8
TA = 115
CYA = 100
CH = 400

I'm currently adding PH increaser to get that up. Normal chlorine demand calculations have not worked for me.
Click to expand...

To begin with your CYA is high. Is it really 100 or is that just the limit of the test used? With a CYA this high it will be hard to get the chems inline. You'll need to replace some water to get it down. I don't see if you have a SWG or not, but your target CYA will depend on your chosen method of chlorination. Replace enough water to hit that CYA level.

Then add enough bleach to bring your pool up to shock levels and hold it there until you loose < 1ppm FC and have <0.5 ppm CC overnight.

All the charts can be found in pool school, or in peoples signature.

hope that helps a little,
dave
 
I agree, you need to bring down the CYA with a couple partial water replacements.

Who knows, your CYA could even be higher! :shock: It's no wonder you can't get a reading for chlorine. :(
 
You can repeat the CYA test with 1/2 pool water 1/2 tap water; double the result. This will tell you if it's really 100, or higher.

duraleigh said:
Typically, we do not use chlorine demand on the forum.
Click to expand...
Not by that name; here it's usually called "getting to know your pool." When you learn that you need to add 1.5ppm or 2ppm or whatever per day to maintain your level, that's your typical chlorine demand, even if we don't call it that.

In extreme cases like this the bucket test can help with planning how many skids of bleach you need to bring home.
--paulr
 
The normal approach is to bring the FC level up to shock level, wait an hour or more, test the FC level, bring it back up to shock level, and so on. You just keep repeating that process until the FC level holds steady overnight.

Having an extreme chlorine demand test result is handy when you are dealing with something like ammonia, which requires a more or less fixed amount of chlorine to deal with. But it can be misleading, because adding chlorine to the entire pool will not always produce the same results as adding chlorine to a bucket for a variety of reasons.
 

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Hi jjoshua,

I agree with the need for a series of partial drains/refills to lower your CYA. It appears from the #'s so far that your pool is overstabilized, which we see all the time.
Folks being Pool Stored so much they can't even enjoy their pools :(

It would be very helpful if you added you pool & equipment specs in your sig. You can do this thru the User Control Panel, upper left, select Profile, then select Edit Sig.

Also, a great test kit. I recommend the TF100 from TFTestKits.Net sold by duraleigh. Link in my sig. Best investment we made in our pool.

Welcome to the forum :wave:
 
I went out and bought a test kit. Here are the results:

FC = 3
TC = 7
CC = 4
PH = 6.8
TA = 180

I also went to my local pool store for a test. They reported similar numbers but also came up with:

TDS = 1850
CYA = 100
 
Pool store gave you CYA 100 twice, which is too high. You should get yourself a CYA test and run your own to be sure. If it is over 100, rerun the test with 1/2 sample water 1/2 tap water and double the result. If it's that high for real you need to drain and refill a bunch of water.

Your TC is outasight... but shocking with such a high CYA is really hard. Do the water replacement first, and then shock afterward.

The refill will make it pointless to do any other adjustments now, it's just a waste of chems.
--paulr
 
It's going to be a few days before I can try to take some water out of the pool. It's only going to be 4-5" at a time anyway. Is there anything I can do with the chemicals to get going with the pH?

BTW, my test strips show minimal CYA.
 
I wouldn't trust the test strip CYA reading at all. The pool store CYA reading is also questionable. Before you do a massive water replacement I would try to get confirmation of your CYA level. By far the best thing is to get your own test kit that can measure CYA, preferably something like the TF100 from TFTestKits.net or the Taylor K-2006.

Adjusting the PH up to around 7.2 is a good idea.
 
This is the scenario that led me to poolforum.com a few years back...the absurdity of it is mind blowing...especially because I went along with it... :grrrr:

Run from that store and NEVER let them test your water again...spend the $80 on a test kit...they were going to have you spend hundreds of $$$ on calcium hypochlorite and your pool would have never been clear again...
 
After you finish filling the pool back up, raise the PH to around 7.2-7.4.

One of the problems with a CYA level of 100 is that the most common CYA test reads CYA levels higher than 100 as 100, so you CYA level might actually be higher. Hopefully it isn't and your current water replacement will get CYA down to a reasonable level.
 

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