Short Cycling

[waterbear]

Dave-

If by drops based kit you mean the kind in which you add drops of OTO solution and compare the color with the samples, that is what I am using. Lowe's carries these kits which max out at 3 ppm and the Walmart kits max out at 5 ppm.

Is there another type of drops based kit? How high will Ben's kit read?

I have owned a pool for 13 years and have never had this type of problem so it is really driving me crazy.

Don

First (I appologize if you already know this but sometimes it's good to start with the basics, I also appoligize for this being somewhat lengthy) there are 3 types of chlorine that needs to be measured:
Free Chlorine (chlorine that is available to act as a sanitizer)
Combine chloine (chorine that has combined with organics in the water and is usually not an effecient sanitizer)
Total chlorine (the total of both FC and CC)

Both FC and TC can be directly measured with the proper tests. CC is found by subtracting the FC from the TC. Ideally your FC and TC measurements should be the same. If they are not it is time to shock.

There are acutally different drop based reagents to test for chlorine

OTO (turns yellow) only measures Total Chlorine. Some people say that if you read it in the first 15 seconds it will give you a free chlorine reading and then let it sit for 2 minutes you can get a total chlorine reading but, IMHO, the results just aren't accurate (Walmart test kit has this in their instructions). It is good for a quick check on your chlorine levels when you know there are no problems or in some situations like yours as PoolDoc indicated.

DPD (turns pink) can measure both Free chlorine and Total Chlorine. It is a much better test but it has drawbacks. the differences in color are sometimes difficult to detect (especially for men) and it can 'bleach out" (turn clear) at chlorine levels above about 10 ppm leading you to believe that you have NO chlorine in the pool when you really have a lot! This can be overcome to an extent by diluting the sample with distilled water and multipling the reading by the dilution factor but this reduces the accuracy and can be time consuming. (dilution can also be used with OTO in the same way andhas the same problems)

FAS-DPD (also pink) is a titration test (pink color will turn clear to give you the reading...endpoint is DISTINCT) that can accurately measure very high chlorine levels (both FC and TC) (up to 50 ppm I believe) with an accuracy up to .2 ppm Combined Chlorine. It takes a bit longer than the other 2 but the results are easier to determine and much more accurate at high clorine levels, which is important when you are dealing with the type of problem you are having.

The general consenus that I have seen on this board (and I agree with it) is that OTO is good for a quick check and that FAS-DPD is good for actually determining your FC and TC.

Ben's kit which is sold on the sister website www.poolsolutions.com has both OTO and FAS-DPD tests in it. Taylor K-2006 is an FAS-DPD test kit. Either one is good. Ben's is a 'better bang for the buck'!

Both Pooldoc and Duraleigh are saying the same thing and it is sound advice. With the type of chlorine demand that you have your chlorine levels will be constanly dropping. You can put the bleach in your pool and then test it later and the level will be down! Algae creates a huge chlorine demand! You need to keep the level up and keep getting it back up.

Pooldoc's post is certainly is worth following since he is our forum moderator and has the experience to back up what he is saying. Dump in at least the amount of bleach he says and keep testing the water with OTO (since you will certainly have combined chlorine and you are really only interested in the total chlorine at this point) and EVERY TIME it drops below 3 ppm add more bleach. This could be several times a day. His note on pH and whether the pool opened with no CYA or high CYA is important. You never stated if the CYA levels are because you just added stabilizer or if they are from before. (the reasons are VERY technical but if you do what he suggests it will certainly be helpful!)

Once the pool clears and your filter is working might then be the time to start testing for CC and to keep the bleach levels up until it is 0 ppm.
As Dave (duraleigh) stated in his post, with a current CYA of 100 ppm you might need to go up to about 25 ppm FC to achive this. This is based on Ben's (PoolDoc) Best guess CYA chart. Here is that thread:
http://www.poolforum.com/pf2/showthread.php?t=365