Green Pool

[arc111]

Hi,
I've been a frequent visitor to this forum for probably 8 years. Thanks for all of the good advice!

I now inherited a pool maintenance problem; 17,000 gallon plaster pool that is green. Sand filter.

The previous pool maintenance was to add tri-chlor tabs.

I had the water tested with the following results:
CYA 100+
pH 6.8
TA 20
FC 1

The testing lady at the pool supply store said that I should disregard the CYA, although the automatic print out said in large bold letters to DRAIN 1/3 OF POOL WATER AND RETEST!

She actually readjusted the CYA level to 90 and reran the test, which resulted in about $150 worth of chemicals recommended. I DID NOT PURCHASE ANYTHING BUT 4 GALLONS OF LIQUID CHLORINE.

I have since raised the pH to 7.2 and the TA to 60 using Borax and baking soda. I have also removed about 1/3 of the water and refilled (before adjusting the pH etc).

I am going to retest and I will post the results this afternoon.

[PoolDoc]

You need to do a dilution, till you get in the range of the test method being used. For example, you can mix your pool water 50:50 with tap water (no CYA!), test, and then multiply the results by 2.

Once you know the actual CYA level, you can determine your correct chlorine level from the Best Guess chart. (link in signature box) .

Of course, you ALSO need to stop using whatever chlorine source is adding all the stabilizer, and switch to either cal hypo or plain bleach.

[arc111]

Tested again today:

ph = 7.5
CYA = 60
TA = 60
FC = 0
TC = .4

I am getting ready to add 3 gallons of household bleach. The pool is green.

Other suggestions appreciated.

Thanks again!

[Watermom]

3 gallons isn't enough. With a CYA of 60, you need to shock the pool up to 20ppm and try and hold it there. In your pool, each gallon (4 quarts) of 6% bleach will add about 3.5ppm of chlorine. Test at least twice per day and each time add enough bleach to get back up to 20. Run the pump 24/7 and backwash whenever the filter pressure rises 5-10psi over clean filter pressure.

BTW -- Welcome to the Pool Forum!

[arc111]

3 gallons isn't enough. With a CYA of 60, you need to shock the pool up to 20ppm and try and hold it there. In your pool, each gallon (4 quarts) of 6% bleach will add about 3.5ppm of chlorine. Test at least twice per day and each time add enough bleach to get back up to 20. Run the pump 24/7 and backwash whenever the filter pressure rises 5-10psi over clean filter pressure.

BTW -- Welcome to the Pool Forum!

I actually added 8 X 3 quart bottles = 6 gallons of 6% bleach. 6 X 3.5 = 21ppm. The cheapo test kit that I have only reads to 10 PPM Chlorine level, but it is at least 10.
I brushed down the pool and will check again in the morning.

Any other suggestions? It has a Hayward sand filter (300 lbs of sand) and I think that it needs 'help'. Should I try adding DE to filter the dead algae? I will try vacuming to waste the worst part of the algae in the morning.

[arc111]

Got everything balanced

pH = 7.5
CYA = 60

6 gallons of household bleach (6%) and the chlorine went to 20 PPM yesterday evening. This morning the chlorine was back down to 3 PPM, so I backwashed and added 2 more gallons of bleach. I plan to add another 2 gallons this evening.

How long will I need to hold the chlorine level to 20 PPM?

THE WATER WAS NOT GREEN, BUT CLOUDY/BLUE THIS MORNING!

[aylad]

Hi, and let me add my welcome!

You need to hold the chlorine level to 20 ppm until 1) the pool clears, 2)you are not losing more than 1 ppm of chlorine when measuring at night after the sun is off the pool, and again in the morning before the sun is on the pool. When both of those conditions are reached, then you can let your chlorine drift back down into the normal ranges for your pool, which are 5-10 ppm....from this point forward, you never want to let your chlorine get below 5 ppm, because doing so is an invitation for more algae problems. And no more trichlor for you!!

The blue water means it's clearing--the cloudiness is the dead algae, which will be removed by the filter. Just keep an eye on your filter pressure and backwash it as the pressure indicates. You can always add DE to the filter to help it along--you just want to add enough to raise your psi by 1 --and that rise may be slow, so add a handful or so, and then check it in 20-30 minutes. IF the pressure went up more than 1 psi, then you can always backwash it out and start over with a smaller amount of DE.

Janet