Can't keep chlorine levels up

[cbednara]

I have a 17x31 Grecian vinyl inground pool. I holds arond 17500 gallons. We this year converted from using Baquacil to Chlorine. I can not keep the chlorine levels up. We are using the pucks in our auto-chlorinator (it "eats" about 3 pucks a week) and 10% liquid chlorine. We are also using an algeside weekly. The pool has been crystal clear since it first cleared up at opening, but the temps have been mild (started in the 70's, in 80's or low 90's most of the time). It is getting a bit cloudy and I notice what looks like "dust in the light" when I have my light on at night.

I have moved the hose on my auto-chlorinator from bottom to top to try to get more water over the pucks.

Early this week we had 0.03 reading on chlorine, so we super shocked it with 4 gallons of 10% liq. Chlorine. The Free Chlorine was reading 5 the next day, but back to 0.01 the following.

Last night at dusk, I put in 2 gallons and the FC reading was all the way back down to 1.3 this morning, I fully expect it to be at 0.X tomorrow.

I am worried with the temp going to be above 100 this week, I am going lose what little contol I have and have a cloudy or worse pool soon.

We live in a farm town, so lots of crops around us and our pool gets no shade.

Any ideas???

[aylad]

Hi cbednara,
Sounds like you've got algae trying to grow. I would shock the pool and hold it at shock level until you can go from dusk one night to just before sunup the next morning without losing more than 1 ppm of chlorine.

Otherwise, what are your test results on your water? Can you please post a set of test results taken with a drop-based kit (no strips!), especially your CYA level?

Welcome to the forum!!

Janet

[cbednara]

I use a LaMotte ColorQ7. Here is my readings from this morning (shocked with 2 gallons of 10% LQ at dusk the night before).

FC -1.38
TC- 1.65
pH - 7.1
TA - 153
CH - 227
CYA - 64

[cbednara]

Also, what would you say is a good FC level as "shock level"?

[Watermom]

Take a look at the Best Guess Chlorine Chart in Janet's signature above. With a CYA reading of 64, your shock level is going to be 20ppm. So, you need to add enough chlorine to get the cl up to 20 right now and as Janet advised, try and hold it there. Your chlorine levels are too low and I'm sure she is right -- you have an algae bloom trying to take over your pool. Don't let it!

You want to hold it at shock level until you can go from sundown one evening to within 2 hours of sunrise the next day without losing more than 1ppm of chlorine and without having a CC reading that is any higher than 0.5ppm and having clear water. At that point, we usually suggest holding the chlorine high for one extra day for added insurance and then you can let the chlorine level drift down and keep it within the minimum and maximum levels based on your CYA reading.

Since your CYA is 64, I would suggest not using the trichlor pucks any more. They are stabilized which means they add CYA and yours is high enough.

Also, your pH is a little low. Bump it up some with some 20 Mule Team Borax (laundry aisle at Walmart).

Hope this helps. Welcome to the Pool Forum!

Oh, almost forgot. Will you please put your pool's information in our Pool Chart. It makes it easier for us to help you.

Pool Chart Entry Form
Pool Chart Results

[PoolDoc]

readings from this morning (shocked with 2 gallons of 10% LQ at dusk the night before).
FC -1.38
TC- 1.65

Pool volume of 17,500 => PF:7

2 gallons of 10% *should* have raised your FC by 12 ppm. There are 3 possibilities: your 10% bleach is actually 2 - 4% (common when bleach is stored at high temps) OR you've got something (like agae as mentioned) creating a high chlorine demand, or you are getting bogus ColorQ readings (it *is* a 'guess-strip' reader!)

Buy 18 gallons of PLAIN 6% store brand bleach from a store with high volume sales (=fresh bleach), like Walmart. Add 6 gallons EACH evening after you get the bleach, and test FC in the AM. You *should* be seeing levels of 20+ ppm in the AM. Also get a cheap OTO drops kit: at 20 ppm, OTO is very dark yellow with an orange tinge. The 2nd evening, brush the heck out of your pool. Also, add the bleach VIA the skimmer, after making sure ALL chemicals, tablets, pills, feeders, etc in the skimmer or pipeline, are removed. Adding the bleach that way will help clean your filter.

By the way, you can test the ColorQ by collecting a sample, and then testing that sample every 20 minutes for an hour. The variations between the results is reflects the minimum (not: maximum) testing error you should assume in every ColorQ result.

[CarlD]

You mentioned using algaecide. What algaecide, namely, what is in it? Are you still using it or did you stop? Algaecides can cause more trouble than they cure. Even Polyquat, the only type we recommend, can cause your FC to drop (I count on it when I'm closing my pool).

I'm not suggesting that stopping using algaecide will stop your problems, but it will reduce them.

[cbednara]

or you are getting bogus ColorQ readings (it *is* a 'guess-strip' ).

Is the lamotte colorq not reputable? Here is a link to what I have. http://www.lamotte.com/component/opt.../mid,/page,19/

I wanted a test kit that used drops of reagent. Reviews were good for what I read and I liked the photometer giving me readings rather than myself eyeballing the color match.

[PoolDoc]

My bad -- I was thinking of the AquaCheck strip reader. The Lamotte ColorQ is

- 3x as expensive as the K2006
+ possibly more accurate than the K2006 on pH and CYA
- probably less accurate on TA and CH
- less accurate on chlorine at low levels
- much less accurate than the K2006 at high levels (> 7 ppm)

I've asked Waterbear (who's been out with surgery) to take a look when he gets a chance. He's played with more test kits than I have. By the way, the K2006 does a titration (color change, not color match) for chlorine, TA, & CH.