Yet another green pool - now getting "blue"

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run53

LifeTime Supporter
May 4, 2010
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New member here. I read all the Pool school and I think it gave me enough base of knowledge to be dangerous. I've owed and maintained my own in-ground pool for several years and fortunately, when i opened mine this past weekend it was crystal clear.

However, the reason I am posting here is not for my pool. I am helping my father with his pool. We opened it up 2 days ago and it was green. I could actually see the bottom of the deep end (16x32 8 ft, 19,000 gallons) and it was covered with green algae. After a brushing, the pool turned to pea soup and has been like that ever since.


Had the water tested at the local pool store last night:

FC 0
TC 0
CC 0
ph 7.0
TA 50
CH 120
CYA 100 (he's used pucks for 20 years).

They suggested 5 gallons of liquid chlorine and brushing. Based on the calculator that should be more than enough to get the FC up to 25 (needed for CYA=100). The calculator suggested about 4 gallons of 12%.

Here's what happened....

1) around 11:00 this morning he put 2 gallons of liquid Chlorine (12%) and 3 packs (1 lb each) of di-chlor and then brushed (I know, that made the CYA problem worse).
2) I get out of work at 5:00pm and picked up 10 gallons of liquid chlorine.

So, I'm sure it is shocked enough (probably too much). By the end of the day (around 8:00pm) the water is still as green as when we started. The filter is a sand filter running 24/7.

One problem is that I don't have a test kit (ordered the TF-100 today) thus I'll have no way of telling what the FC is or how it changes until my kit arrives probably this weekend. I do have test strips but both the TC and FC only go to 10 on the strip so the only thing I know is that the FC was at least 10 when I left his house tonight. So I was planning to keep shocking at 5 gallons/day and brushing until the water turns grey/milky. Does that sound reasonable? I know it would be much easier to to it properly, but he really wanted to get started ASAP so I'm doing this blindly until the kit arrives.

Actually, after we use all the liquid chlorine tomorrow, I suggested that we move to clorox based on what I've read here. I think that means I'll need double since clorox is 6%.

So, again my plan is to add 4-5 gallons (or equivalent clorox) each day and brush until my test kit arrives or until the water turns gray. Hopefully by then I'll have the test kit.

Anything i should be doing differently?

Thanks....
 
Re: Yet another green pool

You can test that water with the tests you have by diluting the sample.

First, he added 3 lbs dichlor which could have brought the FC to 8 plus 2 gal 12% chlorine which adds another 13 FC. You added 5 gallons which adds 33 FC. So while it may have reached 54 FC at some point, you can be sure it is less than that now. ( I am using the calculations provided at the bottom of the Pool Calculator page)

Since you need to get to 25 FC, you should use one portion pool water and 2 portions distilled water and multiply by 3 to get a top end of 30.

Won't be too accurate but that should get you into the ball park. I'd err on the side of above the 25 FC rather than below.
 
Re: Yet another green pool

I am concerned that your CYA level may actually be much higher. The common CYA test will report CYA levels of over 100 as if they are 100. Even if your CYA level is only 100, it is a much better idea to lower your CYA level first, and then fight algae.
 
Re: Yet another green pool

Welcome to TFP! Good on ya for reading Pool School. I can tell that you have some understanding about the situation you are dealing with.

The best thing to do right now is to drain off some water to lose some of that CYA. The amounts of bleach (or any chlorine source for that matter) needed to shock that pool and maintain a good FC relative to the CYA level is going to be enormous. I would drain half the water, fill it back up, get it circulating again, and take a sample to the pool store to test. If you lose half of the water, assuming that the CYA is 100, that should get the CYA level to around 50 and this is a much more manageable situation for you and your FIL to deal with.

I'll tell you though, if he has been using trichlor pucks for years and years without water changes, the actual CYA level may be > 100 ppm. Since 100 is as high as a turbidimetric test can read, he may have this problem.

For now, stay away from the dichlor and tablets, period. Change out some water and we will see where to go from there.
 
Re: Yet another green pool

One thing to remember is most tests for CYA only go upto 100, so if they say you have 100, i could be 500 or more! (pucks for 20 years, could be bad!). Try taking 50% pool water, and 50% tap water and try the test again, hopefully it will read 50, but it may still be 100 (giving you a total reading of 200). More cya the more chlorine needed, over 100 cya will make it very hard to clear your problem up.

<begin edit>
Everybody responded before i could hit submit! Good advice from everybody though, defiantly double check cya and replace water as needed, THEN try to shock.
<end edit>
 
Re: Yet another green pool

Thanks for the quick responses. This place is really great!

I forgot to add that when I tested this evening with a test strip, the CYA showed up in the 30-50 range. So, I guess I'm not sure if i believe the pool store readings or the test strip.

I should also mention that the sample was taken before all the chlorine was added today, and the strip was before I added my 5 gallons of liquid chlorine around 5:00 this evening. Also, the sample that I took to the pool place was sitting in a bottle for about 24 hours before it was tested (I had no choice due to my work schedule and the pool place hours). Would that impact the CYA reading at the pool place?

If the CYA is really 100+, it sounds like the recommendation is to stop wasting the liquid chlorine and empty the pool about half way (and re-filling) before fighting the algae.
 
Re: Yet another green pool

257WbyMag said:
I'll tell you though, if he has been using trichlor pucks for years and years without water changes, the actual CYA level may be > 100 ppm. Since 100 is as high as a turbidimetric test can read, he may have this problem.
Click to expand...


Well, to be honest, he changed his liner about 7-8 years ago, so when I said he was using pucks for 20 years, it was true, but water was changed when he got the new liner. Still 7-8 years of pucks could lead to high CYA. Also, last year he had the same green pool when he opened (eventually got it cleared, but never looked great) and he used a TON of di-clor to shcok with. Yep...I too am nervous about the real CYA reading. Will the TF-100 be able to measure such large amounts?
 
Re: Yet another green pool

I'll go with the pool store test results over the test strips any ol' day.

Yes, if the swim season is long enough, you can end up with too much CYA in a year, much less 7 or 8 years. Depending on the method of delivery, those trichlor tablets can get the CYA up but quick. Dichlor is light years quicker than that too. You need to take the bags of dichlor away from him and hide them.

The TF-100 can only measure to 100 ppm max.

You are correct in that you should stop with the bleach until you get some water changed out. For now, the main issue to focus on is getting the CYA down to a manageable level. Little can be done until then.
 
Re: Yet another green pool

Dale.s said:
The tf-100 will be able too after you use the method i posted above, try 100% pool water to start, then 50/50 pool/tap water if it reads high, more you dilute the lower the accuracy, but at least you get a ballpark figure.
Click to expand...


Yes...thanks to everyone once again. I never would have thought to dilute the water before testing. Great idea. Sounds like those test strips are useless.

I'm curious...... how many CYA tests will I be able to do with my new TF-100 before I need to get more reagents?

Also....I will ask him to start replacing the water a few inches at a time (until it gets to the bottom of the skimmer level) and re-filling. That will be his job, while I'm at work tomorrow. Looks like we should aim for getting CYA down to 50 before wasting any more chlorine.
 

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Re: Yet another green pool

OK...update from this morning.

Before i got a chance to give him the instructions to start emptying the pool to lower the CYA, he had already dumped another 5 gallons of liquid chlorine into the pool.

Anyway, his report was that the water color was significantly lighter green when he got up this morning. Recall this is after dumping all that chlorine into the pool yesterday (still can't see the bottom on shallow end though). in a 6-7 hour period, between the 2 of us we dumped (7) gallons of 12% and (3) lbs. of di-chlor. Before he put the additional 5 gallons in this morning, he stuck a test strip in the pool and the TC/FC was still measuring 10+ (that's as high as the test strips go and I couldn't explain the dilution method to him).

So, I'm guessing that if between the 10+ gallons yesterday and 5 additional ones this morning, it that doesn't start turning the water gray, then the CYA must be sky high.

I did tell him that if no additional change in water color today, we'll have to start draining the pool (about 50%) and retest the CYA. Hopefully I'll have my TF-100 by this weekend so we can stop guessing.
 
Re: Yet another green pool

Well, if he isn't going to take your advice, there is only so much you can do other than encourage. I would continue with the plan to change out water and await the arrival of the TF-100.
 
Re: Yet another green pool

Quick Update....things are looking better after yesterdays dumping of chlorine.

As of 6:30pm this evening, the green color is just about gone, although I can still see some traces of algae on the steps and liner wall (cracks/crevices). I would call it a milky grey color with the slightest green tint. I think this is good news since yesterday before we started, it was dark green (swampy).

Since I still don't have my TF-100 (hopefully this weekend), I am still guessing at bleach amounts. The test strips are still reading off the charts for both TC and FC.

Since it seems to be working (based on the new color), I think we should keep up the shocking while continuing to lower the CYA by replacing water slowly. Problem is I have no idea of how much bleach to use now that it's a milky grayish color. I seem to be beating the algae but i don't want it to make a comeback.

Just to recap, here's what we did................

5/4 @ 11:00am - 2 gallons Liquid Chlorine (12.5) and 3 lbs di-chlor
5/4 @ 6:00pm - 5 gallons 12.5% LC
5/5 @ 10:00am - color improving, still a bit greeinsh. Added 5 gallons 12.5% LC
5/6 @ 6:00pm - milky gray color but still can't see the bottom of shallow end (3.5 ft).

This evening I purchased (10) more bottles of 1.42 gallon bleach (6%).

I am thinking another 3 containers of that tomorrow morning (1.42x3) = 4.26 gallons of 6%. Repeating each of the next 3 mornings with brushing a couple times a day.

I feel like I'm totally blind w/o taking tests but it's working, so I'll keep it up. Does this plan sound reasonable?
 
Re: Yet another green pool - now milky gray

Given the size of the pool - and the high CYA, and the condition of the water.... yes. My reasoning is in your size pool 3 jugs is a little under 10 FC so it certainly won't hurt anything at this point...at least for another day then we can reassess things tomorrow...
 
Re: Yet another green pool - now milky gray

frustratedpoolmom said:
Given the size of the pool - and the high CYA, and the condition of the water.... yes. My reasoning is in your size pool 3 jugs is a little under 10 FC so it certainly won't hurt anything at this point...at least for another day then we can reassess things tomorrow...
Click to expand...

OK....sounds like a plan. But the calculator says that the 3 jugs will raise the FC by 13. The jugs are 1.42 gallons as opposed to 128 oz. jugs.

So I figure that since the strips are always indicating at least 10ppm FC, then I at least get to 23 FC with 3 more jugs. Although probably more since the strips top out at 10ppm.
 
Re: Yet another green pool - now milky gray

Lershac said:
Try some reverse psychology and tell him " we really shouldnt change out half the water" See if that works out.
Click to expand...

I know hear you!

Actually, we are vacuuming to waste, so in fact we are actually slowly changing the water without him even realizing it (although at a slower rate than I'd like). Over time, I'll make sure we work the CYA down to 50 or so. I think that will help his pool stay algae free in the long run without as much need for FC.

I am trying to convince him to stop using the pucks and throwing in di-Chlor to shock.

Making progress.
 

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